| Message ID | 20200224020751.1469-2-xiaoyao.li@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: VMX: Use basic exit reason for cheking and indexing | expand |
Xiaoyao Li <xiaoyao.li@intel.com> writes: > Current kvm uses the 32-bit exit reason to check if it's any specific VM > EXIT, however only the low 16-bit of VM EXIT REASON acts as the basic > exit reason. > > Introduce Macro basic(exit_reaso) "exit_reason" > to help retrieve the basic exit reason > from VM EXIT REASON, and use the basic exit reason for checking and > indexing the exit hanlder. > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> > --- > arch/x86/kvm/vmx/vmx.c | 44 ++++++++++++++++++++++-------------------- > arch/x86/kvm/vmx/vmx.h | 2 ++ > 2 files changed, 25 insertions(+), 21 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 9a6664886f2e..85da72d4dc92 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -1584,7 +1584,7 @@ static int skip_emulated_instruction(struct kvm_vcpu *vcpu) > * i.e. we end up advancing IP with some random value. > */ > if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || > - to_vmx(vcpu)->exit_reason != EXIT_REASON_EPT_MISCONFIG) { > + basic(to_vmx(vcpu)->exit_reason) != EXIT_REASON_EPT_MISCONFIG) { "basic" word is probably 'too basic' to be used for this purpose. Even if we need a macro for it (I'm not really convinced it improves the readability), I'd suggest we name it 'basic_exit_reason()' instead. > rip = kvm_rip_read(vcpu); > rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); > kvm_rip_write(vcpu, rip); > @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > u32 exit_reason = vmx->exit_reason; > + u16 basic_exit_reason = basic(exit_reason); I don't think renaming local variable is needed, let's just do 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the rest of the code as-is. > u32 vectoring_info = vmx->idt_vectoring_info; > > trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX); > @@ -5842,17 +5843,17 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, > * will cause infinite loop. > */ > if ((vectoring_info & VECTORING_INFO_VALID_MASK) && > - (exit_reason != EXIT_REASON_EXCEPTION_NMI && > - exit_reason != EXIT_REASON_EPT_VIOLATION && > - exit_reason != EXIT_REASON_PML_FULL && > - exit_reason != EXIT_REASON_TASK_SWITCH)) { > + (basic_exit_reason != EXIT_REASON_EXCEPTION_NMI && > + basic_exit_reason != EXIT_REASON_EPT_VIOLATION && > + basic_exit_reason != EXIT_REASON_PML_FULL && > + basic_exit_reason != EXIT_REASON_TASK_SWITCH)) { > vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; > vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_DELIVERY_EV; > vcpu->run->internal.ndata = 3; > vcpu->run->internal.data[0] = vectoring_info; > vcpu->run->internal.data[1] = exit_reason; > vcpu->run->internal.data[2] = vcpu->arch.exit_qualification; > - if (exit_reason == EXIT_REASON_EPT_MISCONFIG) { > + if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) { > vcpu->run->internal.ndata++; > vcpu->run->internal.data[3] = > vmcs_read64(GUEST_PHYSICAL_ADDRESS); > @@ -5884,32 +5885,32 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, > return 1; > } > > - if (exit_reason >= kvm_vmx_max_exit_handlers) > + if (basic_exit_reason >= kvm_vmx_max_exit_handlers) > goto unexpected_vmexit; > #ifdef CONFIG_RETPOLINE > - if (exit_reason == EXIT_REASON_MSR_WRITE) > + if (basic_exit_reason == EXIT_REASON_MSR_WRITE) > return kvm_emulate_wrmsr(vcpu); > - else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER) > + else if (basic_exit_reason == EXIT_REASON_PREEMPTION_TIMER) > return handle_preemption_timer(vcpu); > - else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW) > + else if (basic_exit_reason == EXIT_REASON_INTERRUPT_WINDOW) > return handle_interrupt_window(vcpu); > - else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) > + else if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) > return handle_external_interrupt(vcpu); > - else if (exit_reason == EXIT_REASON_HLT) > + else if (basic_exit_reason == EXIT_REASON_HLT) > return kvm_emulate_halt(vcpu); > - else if (exit_reason == EXIT_REASON_EPT_MISCONFIG) > + else if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) > return handle_ept_misconfig(vcpu); > #endif > > - exit_reason = array_index_nospec(exit_reason, > + basic_exit_reason = array_index_nospec(basic_exit_reason, > kvm_vmx_max_exit_handlers); > - if (!kvm_vmx_exit_handlers[exit_reason]) > + if (!kvm_vmx_exit_handlers[basic_exit_reason]) > goto unexpected_vmexit; > > - return kvm_vmx_exit_handlers[exit_reason](vcpu); > + return kvm_vmx_exit_handlers[basic_exit_reason](vcpu); > > unexpected_vmexit: > - vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason); > + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", basic_exit_reason); > dump_vmcs(); > vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; > vcpu->run->internal.suberror = > @@ -6241,13 +6242,14 @@ static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu, > enum exit_fastpath_completion *exit_fastpath) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > + u16 basic_exit_reason = basic(vmx->exit_reason); Here I'd suggest we also use the same 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' as above. > > - if (vmx->exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) > + if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) > handle_external_interrupt_irqoff(vcpu); > - else if (vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI) > + else if (basic_exit_reason == EXIT_REASON_EXCEPTION_NMI) > handle_exception_nmi_irqoff(vmx); > else if (!is_guest_mode(vcpu) && > - vmx->exit_reason == EXIT_REASON_MSR_WRITE) > + basic_exit_reason == EXIT_REASON_MSR_WRITE) > *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu); > } > > @@ -6621,7 +6623,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) > vmx->idt_vectoring_info = 0; > > vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); > - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) > + if (basic(vmx->exit_reason) == EXIT_REASON_MCE_DURING_VMENTRY) > kvm_machine_check(); > > if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index 7f42cf3dcd70..c6ba33eedb59 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -22,6 +22,8 @@ extern u32 get_umwait_control_msr(void); > > #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4)) > > +#define basic(exit_reason) ((u16)(exit_reason)) > + > #ifdef CONFIG_X86_64 > #define NR_SHARED_MSRS 7 > #else
On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: > Xiaoyao Li <xiaoyao.li@intel.com> writes: > >> Current kvm uses the 32-bit exit reason to check if it's any specific VM >> EXIT, however only the low 16-bit of VM EXIT REASON acts as the basic >> exit reason. >> >> Introduce Macro basic(exit_reaso) > > "exit_reason" Ah, will correct it in v2. >> to help retrieve the basic exit reason >> from VM EXIT REASON, and use the basic exit reason for checking and >> indexing the exit hanlder. >> >> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> >> --- >> arch/x86/kvm/vmx/vmx.c | 44 ++++++++++++++++++++++-------------------- >> arch/x86/kvm/vmx/vmx.h | 2 ++ >> 2 files changed, 25 insertions(+), 21 deletions(-) >> >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> index 9a6664886f2e..85da72d4dc92 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -1584,7 +1584,7 @@ static int skip_emulated_instruction(struct kvm_vcpu *vcpu) >> * i.e. we end up advancing IP with some random value. >> */ >> if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || >> - to_vmx(vcpu)->exit_reason != EXIT_REASON_EPT_MISCONFIG) { >> + basic(to_vmx(vcpu)->exit_reason) != EXIT_REASON_EPT_MISCONFIG) { > > "basic" word is probably 'too basic' to be used for this purpose. Even > if we need a macro for it (I'm not really convinced it improves the > readability), I'd suggest we name it 'basic_exit_reason()' instead. Agreed. >> rip = kvm_rip_read(vcpu); >> rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); >> kvm_rip_write(vcpu, rip); >> @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >> { >> struct vcpu_vmx *vmx = to_vmx(vcpu); >> u32 exit_reason = vmx->exit_reason; >> + u16 basic_exit_reason = basic(exit_reason); > > I don't think renaming local variable is needed, let's just do > > 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the > rest of the code as-is. No, we can't do this. It's not just renaming local variable, the full 32-bit exit reason is used elsewhere in this function that needs the upper 16-bit. Here variable basic_exit_reason is added for the cases where only basic exit reason number is needed. >> u32 vectoring_info = vmx->idt_vectoring_info; >> >> trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX); >> @@ -5842,17 +5843,17 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >> * will cause infinite loop. >> */ >> if ((vectoring_info & VECTORING_INFO_VALID_MASK) && >> - (exit_reason != EXIT_REASON_EXCEPTION_NMI && >> - exit_reason != EXIT_REASON_EPT_VIOLATION && >> - exit_reason != EXIT_REASON_PML_FULL && >> - exit_reason != EXIT_REASON_TASK_SWITCH)) { >> + (basic_exit_reason != EXIT_REASON_EXCEPTION_NMI && >> + basic_exit_reason != EXIT_REASON_EPT_VIOLATION && >> + basic_exit_reason != EXIT_REASON_PML_FULL && >> + basic_exit_reason != EXIT_REASON_TASK_SWITCH)) { >> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >> vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_DELIVERY_EV; >> vcpu->run->internal.ndata = 3; >> vcpu->run->internal.data[0] = vectoring_info; >> vcpu->run->internal.data[1] = exit_reason; >> vcpu->run->internal.data[2] = vcpu->arch.exit_qualification; >> - if (exit_reason == EXIT_REASON_EPT_MISCONFIG) { >> + if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) { >> vcpu->run->internal.ndata++; >> vcpu->run->internal.data[3] = >> vmcs_read64(GUEST_PHYSICAL_ADDRESS); >> @@ -5884,32 +5885,32 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >> return 1; >> } >> >> - if (exit_reason >= kvm_vmx_max_exit_handlers) >> + if (basic_exit_reason >= kvm_vmx_max_exit_handlers) >> goto unexpected_vmexit; >> #ifdef CONFIG_RETPOLINE >> - if (exit_reason == EXIT_REASON_MSR_WRITE) >> + if (basic_exit_reason == EXIT_REASON_MSR_WRITE) >> return kvm_emulate_wrmsr(vcpu); >> - else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER) >> + else if (basic_exit_reason == EXIT_REASON_PREEMPTION_TIMER) >> return handle_preemption_timer(vcpu); >> - else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW) >> + else if (basic_exit_reason == EXIT_REASON_INTERRUPT_WINDOW) >> return handle_interrupt_window(vcpu); >> - else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >> + else if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >> return handle_external_interrupt(vcpu); >> - else if (exit_reason == EXIT_REASON_HLT) >> + else if (basic_exit_reason == EXIT_REASON_HLT) >> return kvm_emulate_halt(vcpu); >> - else if (exit_reason == EXIT_REASON_EPT_MISCONFIG) >> + else if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) >> return handle_ept_misconfig(vcpu); >> #endif >> >> - exit_reason = array_index_nospec(exit_reason, >> + basic_exit_reason = array_index_nospec(basic_exit_reason, >> kvm_vmx_max_exit_handlers); >> - if (!kvm_vmx_exit_handlers[exit_reason]) >> + if (!kvm_vmx_exit_handlers[basic_exit_reason]) >> goto unexpected_vmexit; >> >> - return kvm_vmx_exit_handlers[exit_reason](vcpu); >> + return kvm_vmx_exit_handlers[basic_exit_reason](vcpu); >> >> unexpected_vmexit: >> - vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason); >> + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", basic_exit_reason); >> dump_vmcs(); >> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >> vcpu->run->internal.suberror = >> @@ -6241,13 +6242,14 @@ static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu, >> enum exit_fastpath_completion *exit_fastpath) >> { >> struct vcpu_vmx *vmx = to_vmx(vcpu); >> + u16 basic_exit_reason = basic(vmx->exit_reason); > > Here I'd suggest we also use the same > > 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' > > as above. > >> >> - if (vmx->exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >> + if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >> handle_external_interrupt_irqoff(vcpu); >> - else if (vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI) >> + else if (basic_exit_reason == EXIT_REASON_EXCEPTION_NMI) >> handle_exception_nmi_irqoff(vmx); >> else if (!is_guest_mode(vcpu) && >> - vmx->exit_reason == EXIT_REASON_MSR_WRITE) >> + basic_exit_reason == EXIT_REASON_MSR_WRITE) >> *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu); >> } >> >> @@ -6621,7 +6623,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) >> vmx->idt_vectoring_info = 0; >> >> vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); >> - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) >> + if (basic(vmx->exit_reason) == EXIT_REASON_MCE_DURING_VMENTRY) >> kvm_machine_check(); >> >> if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) >> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h >> index 7f42cf3dcd70..c6ba33eedb59 100644 >> --- a/arch/x86/kvm/vmx/vmx.h >> +++ b/arch/x86/kvm/vmx/vmx.h >> @@ -22,6 +22,8 @@ extern u32 get_umwait_control_msr(void); >> >> #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4)) >> >> +#define basic(exit_reason) ((u16)(exit_reason)) >> + >> #ifdef CONFIG_X86_64 >> #define NR_SHARED_MSRS 7 >> #else >
Xiaoyao Li <xiaoyao.li@intel.com> writes: > On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: >> Xiaoyao Li <xiaoyao.li@intel.com> writes: >> ... >>> rip = kvm_rip_read(vcpu); >>> rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); >>> kvm_rip_write(vcpu, rip); >>> @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >>> { >>> struct vcpu_vmx *vmx = to_vmx(vcpu); >>> u32 exit_reason = vmx->exit_reason; >>> + u16 basic_exit_reason = basic(exit_reason); >> >> I don't think renaming local variable is needed, let's just do >> >> 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the >> rest of the code as-is. > > No, we can't do this. > > It's not just renaming local variable, the full 32-bit exit reason is > used elsewhere in this function that needs the upper 16-bit. > > Here variable basic_exit_reason is added for the cases where only basic > exit reason number is needed. > Can we do the other way around, i.e. introduce 'extended_exit_reason' and use it where all 32 bits are needed? I'm fine with the change, just trying to minimize the (unneeded) code churn.
On Mon, Feb 24, 2020 at 02:04:46PM +0100, Vitaly Kuznetsov wrote: > Xiaoyao Li <xiaoyao.li@intel.com> writes: > > > On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: > >> Xiaoyao Li <xiaoyao.li@intel.com> writes: > >> > > ... > > >>> rip = kvm_rip_read(vcpu); > >>> rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); > >>> kvm_rip_write(vcpu, rip); > >>> @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, > >>> { > >>> struct vcpu_vmx *vmx = to_vmx(vcpu); > >>> u32 exit_reason = vmx->exit_reason; > >>> + u16 basic_exit_reason = basic(exit_reason); > >> > >> I don't think renaming local variable is needed, let's just do > >> > >> 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the > >> rest of the code as-is. > > > > No, we can't do this. > > > > It's not just renaming local variable, the full 32-bit exit reason is > > used elsewhere in this function that needs the upper 16-bit. > > > > Here variable basic_exit_reason is added for the cases where only basic > > exit reason number is needed. > > > > Can we do the other way around, i.e. introduce 'extended_exit_reason' > and use it where all 32 bits are needed? I'm fine with the change, just > trying to minimize the (unneeded) code churn. 100% agree. Even better than adding a second field to vcpu_vmx would be to make it a union, though we'd probably want to call it something like full_exit_reason in that case. That should give us compile-time checks on exit_reason, e.g. if we try to query one of the upper bits using a u16, e.g. --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5818,7 +5818,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) return nested_vmx_reflect_vmexit(vcpu, exit_reason); - if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { + if (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { dump_vmcs(); vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY; vcpu->run->fail_entry.hardware_entry_failure_reason @@ -6620,11 +6620,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) vmx->nested.nested_run_pending = 0; vmx->idt_vectoring_info = 0; - vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) + vmx->full_exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); + if (vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) kvm_machine_check(); - if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) + if (vmx->fail || + (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) return; vmx->loaded_vmcs->launched = 1; diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 7f42cf3dcd70..60c09640ea59 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -260,7 +260,10 @@ struct vcpu_vmx { int vpid; bool emulation_required; - u32 exit_reason; + union { + u16 exit_reason; + u32 full_exit_reason; + } /* Posted interrupt descriptor */ struct pi_desc pi_desc; > -- > Vitaly >
On 2/25/2020 12:17 AM, Sean Christopherson wrote: > On Mon, Feb 24, 2020 at 02:04:46PM +0100, Vitaly Kuznetsov wrote: >> Xiaoyao Li <xiaoyao.li@intel.com> writes: >> >>> On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: >>>> Xiaoyao Li <xiaoyao.li@intel.com> writes: >>>> >> >> ... >> >>>>> rip = kvm_rip_read(vcpu); >>>>> rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); >>>>> kvm_rip_write(vcpu, rip); >>>>> @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >>>>> { >>>>> struct vcpu_vmx *vmx = to_vmx(vcpu); >>>>> u32 exit_reason = vmx->exit_reason; >>>>> + u16 basic_exit_reason = basic(exit_reason); >>>> >>>> I don't think renaming local variable is needed, let's just do >>>> >>>> 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the >>>> rest of the code as-is. >>> >>> No, we can't do this. >>> >>> It's not just renaming local variable, the full 32-bit exit reason is >>> used elsewhere in this function that needs the upper 16-bit. >>> >>> Here variable basic_exit_reason is added for the cases where only basic >>> exit reason number is needed. >>> >> >> Can we do the other way around, i.e. introduce 'extended_exit_reason' >> and use it where all 32 bits are needed? I'm fine with the change, just >> trying to minimize the (unneeded) code churn. > > 100% agree. Even better than adding a second field to vcpu_vmx would be > to make it a union, though we'd probably want to call it something like > full_exit_reason in that case. That should give us compile-time checks on > exit_reason, e.g. if we try to query one of the upper bits using a u16, e.g. I have thought about union, but it seems union { u16 exit_reason; u32 full_exit_reason; } is not a good name. Since there are many codes in vmx.c and nested.c assume that exit_reason stands for 32-bit EXIT REASON vmcs field as well as evmcs->vm_exit_reason and vmcs12->vm_exit_reason. Do we really want to also rename them to full_exit_reason? Maybe we name it union { u16 basic_exit_reason; u32 exit_reason; } as what SDM defines? > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -5818,7 +5818,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, > if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) > return nested_vmx_reflect_vmexit(vcpu, exit_reason); > > - if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { > + if (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { > dump_vmcs(); > vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY; > vcpu->run->fail_entry.hardware_entry_failure_reason > @@ -6620,11 +6620,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) > vmx->nested.nested_run_pending = 0; > vmx->idt_vectoring_info = 0; > > - vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); > - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) > + vmx->full_exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); > + if (vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) > kvm_machine_check(); > > - if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) > + if (vmx->fail || > + (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) > return; > > vmx->loaded_vmcs->launched = 1; > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index 7f42cf3dcd70..60c09640ea59 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -260,7 +260,10 @@ struct vcpu_vmx { > int vpid; > bool emulation_required; > > - u32 exit_reason; > + union { > + u16 exit_reason; > + u32 full_exit_reason; > + } > > /* Posted interrupt descriptor */ > struct pi_desc pi_desc; > > > > > >> -- >> Vitaly >>
On 02/24/2020 04:01 AM, Xiaoyao Li wrote: > On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: >> Xiaoyao Li <xiaoyao.li@intel.com> writes: >> >>> Current kvm uses the 32-bit exit reason to check if it's any >>> specific VM >>> EXIT, however only the low 16-bit of VM EXIT REASON acts as the basic >>> exit reason. >>> >>> Introduce Macro basic(exit_reaso) >> >> "exit_reason" > > Ah, will correct it in v2. > >>> to help retrieve the basic exit reason >>> from VM EXIT REASON, and use the basic exit reason for checking and >>> indexing the exit hanlder. >>> >>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> >>> --- >>> arch/x86/kvm/vmx/vmx.c | 44 >>> ++++++++++++++++++++++-------------------- >>> arch/x86/kvm/vmx/vmx.h | 2 ++ >>> 2 files changed, 25 insertions(+), 21 deletions(-) >>> >>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >>> index 9a6664886f2e..85da72d4dc92 100644 >>> --- a/arch/x86/kvm/vmx/vmx.c >>> +++ b/arch/x86/kvm/vmx/vmx.c >>> @@ -1584,7 +1584,7 @@ static int skip_emulated_instruction(struct >>> kvm_vcpu *vcpu) >>> * i.e. we end up advancing IP with some random value. >>> */ >>> if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || >>> - to_vmx(vcpu)->exit_reason != EXIT_REASON_EPT_MISCONFIG) { >>> + basic(to_vmx(vcpu)->exit_reason) != >>> EXIT_REASON_EPT_MISCONFIG) { >> >> "basic" word is probably 'too basic' to be used for this purpose. Even >> if we need a macro for it (I'm not really convinced it improves the >> readability), I'd suggest we name it 'basic_exit_reason()' instead. > > Agreed. > >>> rip = kvm_rip_read(vcpu); >>> rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); >>> kvm_rip_write(vcpu, rip); >>> @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >>> { >>> struct vcpu_vmx *vmx = to_vmx(vcpu); >>> u32 exit_reason = vmx->exit_reason; >>> + u16 basic_exit_reason = basic(exit_reason); >> >> I don't think renaming local variable is needed, let's just do >> >> 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' and keep the >> rest of the code as-is. > > No, we can't do this. > > It's not just renaming local variable, the full 32-bit exit reason is > used elsewhere in this function that needs the upper 16-bit. > > Here variable basic_exit_reason is added for the cases where only > basic exit reason number is needed. > >>> u32 vectoring_info = vmx->idt_vectoring_info; >>> trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX); >>> @@ -5842,17 +5843,17 @@ static int vmx_handle_exit(struct kvm_vcpu >>> *vcpu, >>> * will cause infinite loop. >>> */ >>> if ((vectoring_info & VECTORING_INFO_VALID_MASK) && >>> - (exit_reason != EXIT_REASON_EXCEPTION_NMI && >>> - exit_reason != EXIT_REASON_EPT_VIOLATION && >>> - exit_reason != EXIT_REASON_PML_FULL && >>> - exit_reason != EXIT_REASON_TASK_SWITCH)) { >>> + (basic_exit_reason != EXIT_REASON_EXCEPTION_NMI && >>> + basic_exit_reason != EXIT_REASON_EPT_VIOLATION && >>> + basic_exit_reason != EXIT_REASON_PML_FULL && >>> + basic_exit_reason != EXIT_REASON_TASK_SWITCH)) { >>> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >>> vcpu->run->internal.suberror = >>> KVM_INTERNAL_ERROR_DELIVERY_EV; >>> vcpu->run->internal.ndata = 3; >>> vcpu->run->internal.data[0] = vectoring_info; >>> vcpu->run->internal.data[1] = exit_reason; >>> vcpu->run->internal.data[2] = vcpu->arch.exit_qualification; >>> - if (exit_reason == EXIT_REASON_EPT_MISCONFIG) { >>> + if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) { >>> vcpu->run->internal.ndata++; >>> vcpu->run->internal.data[3] = >>> vmcs_read64(GUEST_PHYSICAL_ADDRESS); >>> @@ -5884,32 +5885,32 @@ static int vmx_handle_exit(struct kvm_vcpu >>> *vcpu, >>> return 1; >>> } >>> - if (exit_reason >= kvm_vmx_max_exit_handlers) >>> + if (basic_exit_reason >= kvm_vmx_max_exit_handlers) >>> goto unexpected_vmexit; >>> #ifdef CONFIG_RETPOLINE >>> - if (exit_reason == EXIT_REASON_MSR_WRITE) >>> + if (basic_exit_reason == EXIT_REASON_MSR_WRITE) >>> return kvm_emulate_wrmsr(vcpu); >>> - else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER) >>> + else if (basic_exit_reason == EXIT_REASON_PREEMPTION_TIMER) >>> return handle_preemption_timer(vcpu); >>> - else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW) >>> + else if (basic_exit_reason == EXIT_REASON_INTERRUPT_WINDOW) >>> return handle_interrupt_window(vcpu); >>> - else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >>> + else if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >>> return handle_external_interrupt(vcpu); >>> - else if (exit_reason == EXIT_REASON_HLT) >>> + else if (basic_exit_reason == EXIT_REASON_HLT) >>> return kvm_emulate_halt(vcpu); >>> - else if (exit_reason == EXIT_REASON_EPT_MISCONFIG) >>> + else if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) >>> return handle_ept_misconfig(vcpu); >>> #endif >>> - exit_reason = array_index_nospec(exit_reason, >>> + basic_exit_reason = array_index_nospec(basic_exit_reason, >>> kvm_vmx_max_exit_handlers); >>> - if (!kvm_vmx_exit_handlers[exit_reason]) >>> + if (!kvm_vmx_exit_handlers[basic_exit_reason]) >>> goto unexpected_vmexit; >>> - return kvm_vmx_exit_handlers[exit_reason](vcpu); >>> + return kvm_vmx_exit_handlers[basic_exit_reason](vcpu); >>> unexpected_vmexit: >>> - vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", >>> exit_reason); >>> + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", >>> basic_exit_reason); >>> dump_vmcs(); >>> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >>> vcpu->run->internal.suberror = >>> @@ -6241,13 +6242,14 @@ static void vmx_handle_exit_irqoff(struct >>> kvm_vcpu *vcpu, >>> enum exit_fastpath_completion *exit_fastpath) >>> { >>> struct vcpu_vmx *vmx = to_vmx(vcpu); >>> + u16 basic_exit_reason = basic(vmx->exit_reason); >> >> Here I'd suggest we also use the same >> >> 'u16 exit_reason = basic_exit_reason(vmx->exit_reason)' >> >> as above. >> >>> - if (vmx->exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >>> + if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) >>> handle_external_interrupt_irqoff(vcpu); >>> - else if (vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI) >>> + else if (basic_exit_reason == EXIT_REASON_EXCEPTION_NMI) >>> handle_exception_nmi_irqoff(vmx); >>> else if (!is_guest_mode(vcpu) && >>> - vmx->exit_reason == EXIT_REASON_MSR_WRITE) >>> + basic_exit_reason == EXIT_REASON_MSR_WRITE) >>> *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu); >>> } >>> @@ -6621,7 +6623,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) >>> vmx->idt_vectoring_info = 0; >>> vmx->exit_reason = vmx->fail ? 0xdead : >>> vmcs_read32(VM_EXIT_REASON); >>> - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) >>> + if (basic(vmx->exit_reason) == EXIT_REASON_MCE_DURING_VMENTRY) >>> kvm_machine_check(); >>> if (vmx->fail || (vmx->exit_reason & >>> VMX_EXIT_REASONS_FAILED_VMENTRY)) >>> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h >>> index 7f42cf3dcd70..c6ba33eedb59 100644 >>> --- a/arch/x86/kvm/vmx/vmx.h >>> +++ b/arch/x86/kvm/vmx/vmx.h >>> @@ -22,6 +22,8 @@ extern u32 get_umwait_control_msr(void); >>> #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4)) >>> +#define basic(exit_reason) ((u16)(exit_reason)) We have a macro for bit 31, VMX_EXIT_REASONS_FAILED_VMENTRY 0x80000000 Does it make sense to define a macro like that instead ? Say, VMX_BASIC_EXIT_REASON 0x0000ffff and then we do, u32 exit_reason = vmx->exit_reason; u16 basic_exit_reason = exit_reason & VMX_BASIC_EXIT_REASON; >>> + >>> #ifdef CONFIG_X86_64 >>> #define NR_SHARED_MSRS 7 >>> #else >> >
On Tue, Feb 25, 2020 at 08:13:15AM +0800, Xiaoyao Li wrote: > On 2/25/2020 12:17 AM, Sean Christopherson wrote: > >On Mon, Feb 24, 2020 at 02:04:46PM +0100, Vitaly Kuznetsov wrote: > >>Xiaoyao Li <xiaoyao.li@intel.com> writes: > >> > >>>On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: > >>>>Xiaoyao Li <xiaoyao.li@intel.com> writes: > >>>> > >>>Here variable basic_exit_reason is added for the cases where only basic > >>>exit reason number is needed. > >>> > >> > >>Can we do the other way around, i.e. introduce 'extended_exit_reason' > >>and use it where all 32 bits are needed? I'm fine with the change, just > >>trying to minimize the (unneeded) code churn. > > > >100% agree. Even better than adding a second field to vcpu_vmx would be > >to make it a union, though we'd probably want to call it something like > >full_exit_reason in that case. That should give us compile-time checks on > >exit_reason, e.g. if we try to query one of the upper bits using a u16, e.g. > > I have thought about union, but it seems > > union { > u16 exit_reason; > u32 full_exit_reason; > } > > is not a good name. Since there are many codes in vmx.c and nested.c assume > that exit_reason stands for 32-bit EXIT REASON vmcs field as well as > evmcs->vm_exit_reason and vmcs12->vm_exit_reason. Do we really want to also > rename them to full_exit_reason? It's actually the opposite, almost all of the VMX code assumes exit_reason holds only the basic exit reason, i.e. a 16-bit value. For example, SGX adds a modifier flag to denote a VM-Exit was from enclave mode, and that bit needs to be stripped from exit_reason, otherwise all the checks like "if (exit_reason == blah_blah_blah)" fail. Making exit_reason a 16-bit alias of the full/extended exit_reason neatly sidesteps that issue. And it is an issue that has caused actual problems in the past, e.g. see commit beb8d93b3e42 ("KVM: VMX: Fix handling of #MC that occurs during VM-Entry"). Coincidentally, that commit also removes a local "u16 basic_exit_reason" :-). Except for one mistake, the pseudo-patch below is the entirety of required changes. Most (all?) of the functions that take "u32 exit_reason" can (and should) continue to take a u32. As for the name, I strongly prefer keeping the exit_reason name for the basic exit reason. The vast majority of VM-Exits do not have modifiers set, i.e. "basic exit reason" == vmcs.EXIT_REASON for nearly all normal usage. This holds true in every form of communication, e.g. when discussing VM-Exit reasons, it's never qualified with "basic", it's simply the exit reason. IMO the code is better off following the colloquial usage of "exit reason". A simple comment above the union would suffice to clear up any confusion with respect to the SDM. > Maybe we name it > > union { > u16 basic_exit_reason; > u32 exit_reason; > } > > as what SDM defines? > > >--- a/arch/x86/kvm/vmx/vmx.c > >+++ b/arch/x86/kvm/vmx/vmx.c > >@@ -5818,7 +5818,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, > > if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) > > return nested_vmx_reflect_vmexit(vcpu, exit_reason); > > > >- if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { > >+ if (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { If we do go the union route, this snippet of code is insufficient, the full/extended exit reason needs to be snapshotted early for use in the tracepoint and in fail_entry.hardware_entry_failure_reason. > > dump_vmcs(); > > vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY; > > vcpu->run->fail_entry.hardware_entry_failure_reason > >@@ -6620,11 +6620,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) > > vmx->nested.nested_run_pending = 0; > > vmx->idt_vectoring_info = 0; > > > >- vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); > >- if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) > >+ vmx->full_exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); > >+ if (vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) > > kvm_machine_check(); > > > >- if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) > >+ if (vmx->fail || > >+ (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) > > return; > > > > vmx->loaded_vmcs->launched = 1; > >diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > >index 7f42cf3dcd70..60c09640ea59 100644 > >--- a/arch/x86/kvm/vmx/vmx.h > >+++ b/arch/x86/kvm/vmx/vmx.h > >@@ -260,7 +260,10 @@ struct vcpu_vmx { > > int vpid; > > bool emulation_required; > > > >- u32 exit_reason; > >+ union { > >+ u16 exit_reason; > >+ u32 full_exit_reason; > >+ } > > > > /* Posted interrupt descriptor */ > > struct pi_desc pi_desc; > > > > > > > > > > > >>-- > >>Vitaly > >> >
On 2/25/2020 2:13 PM, Sean Christopherson wrote: > On Tue, Feb 25, 2020 at 08:13:15AM +0800, Xiaoyao Li wrote: >> On 2/25/2020 12:17 AM, Sean Christopherson wrote: >>> On Mon, Feb 24, 2020 at 02:04:46PM +0100, Vitaly Kuznetsov wrote: >>>> Xiaoyao Li <xiaoyao.li@intel.com> writes: >>>> >>>>> On 2/24/2020 6:16 PM, Vitaly Kuznetsov wrote: >>>>>> Xiaoyao Li <xiaoyao.li@intel.com> writes: >>>>>> >>>>> Here variable basic_exit_reason is added for the cases where only basic >>>>> exit reason number is needed. >>>>> >>>> >>>> Can we do the other way around, i.e. introduce 'extended_exit_reason' >>>> and use it where all 32 bits are needed? I'm fine with the change, just >>>> trying to minimize the (unneeded) code churn. >>> >>> 100% agree. Even better than adding a second field to vcpu_vmx would be >>> to make it a union, though we'd probably want to call it something like >>> full_exit_reason in that case. That should give us compile-time checks on >>> exit_reason, e.g. if we try to query one of the upper bits using a u16, e.g. >> >> I have thought about union, but it seems >> >> union { >> u16 exit_reason; >> u32 full_exit_reason; >> } >> >> is not a good name. Since there are many codes in vmx.c and nested.c assume >> that exit_reason stands for 32-bit EXIT REASON vmcs field as well as >> evmcs->vm_exit_reason and vmcs12->vm_exit_reason. Do we really want to also >> rename them to full_exit_reason? > > It's actually the opposite, almost all of the VMX code assumes exit_reason > holds only the basic exit reason, i.e. a 16-bit value. For example, SGX > adds a modifier flag to denote a VM-Exit was from enclave mode, and that > bit needs to be stripped from exit_reason, otherwise all the checks like > "if (exit_reason == blah_blah_blah)" fail. > > Making exit_reason a 16-bit alias of the full/extended exit_reason neatly > sidesteps that issue. And it is an issue that has caused actual problems > in the past, e.g. see commit beb8d93b3e42 ("KVM: VMX: Fix handling of #MC > that occurs during VM-Entry"). Coincidentally, that commit also removes a > local "u16 basic_exit_reason" :-). > > Except for one mistake, the pseudo-patch below is the entirety of required > changes. Most (all?) of the functions that take "u32 exit_reason" can (and > should) continue to take a u32. > > As for the name, I strongly prefer keeping the exit_reason name for the > basic exit reason. The vast majority of VM-Exits do not have modifiers > set, i.e. "basic exit reason" == vmcs.EXIT_REASON for nearly all normal > usage. This holds true in every form of communication, e.g. when discussing > VM-Exit reasons, it's never qualified with "basic", it's simply the exit > reason. IMO the code is better off following the colloquial usage of "exit > reason". A simple comment above the union would suffice to clear up any > confusion with respect to the SDM. Well, for this reason we can keep exit_reason for 16-bit usage, and define full/extended_exit_reason for 32-bit cases. This makes less code churn. But after we choose to use exit_reason and full/extended_exit_reason, what if someday new modifier flags are added and we want to enable some modifier flags for nested case? I guess we need to change existing exit_reason to full/extended_exit_reason in nested.c/nested.h to keep the naming rule consistent. >> Maybe we name it >> >> union { >> u16 basic_exit_reason; >> u32 exit_reason; >> } >> >> as what SDM defines? >> >>> --- a/arch/x86/kvm/vmx/vmx.c >>> +++ b/arch/x86/kvm/vmx/vmx.c >>> @@ -5818,7 +5818,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, >>> if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) >>> return nested_vmx_reflect_vmexit(vcpu, exit_reason); >>> >>> - if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { >>> + if (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) { > > If we do go the union route, this snippet of code is insufficient, the > full/extended exit reason needs to be snapshotted early for use in the > tracepoint and in fail_entry.hardware_entry_failure_reason. > >>> dump_vmcs(); >>> vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY; >>> vcpu->run->fail_entry.hardware_entry_failure_reason >>> @@ -6620,11 +6620,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) >>> vmx->nested.nested_run_pending = 0; >>> vmx->idt_vectoring_info = 0; >>> >>> - vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); >>> - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) >>> + vmx->full_exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); >>> + if (vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) >>> kvm_machine_check(); >>> >>> - if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) >>> + if (vmx->fail || >>> + (vmx->full_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) >>> return; >>> >>> vmx->loaded_vmcs->launched = 1; >>> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h >>> index 7f42cf3dcd70..60c09640ea59 100644 >>> --- a/arch/x86/kvm/vmx/vmx.h >>> +++ b/arch/x86/kvm/vmx/vmx.h >>> @@ -260,7 +260,10 @@ struct vcpu_vmx { >>> int vpid; >>> bool emulation_required; >>> >>> - u32 exit_reason; >>> + union { >>> + u16 exit_reason; >>> + u32 full_exit_reason; >>> + } >>> >>> /* Posted interrupt descriptor */ >>> struct pi_desc pi_desc; >>> >>> >>> >>> >>> >>>> -- >>>> Vitaly >>>> >>
Krish Sadhukhan <krish.sadhukhan@oracle.com> writes: > > We have a macro for bit 31, > > VMX_EXIT_REASONS_FAILED_VMENTRY 0x80000000 > > > Does it make sense to define a macro like that instead ? Say, > > VMX_BASIC_EXIT_REASON 0x0000ffff > 0xffffU ? > and then we do, > > u32 exit_reason = vmx->exit_reason; > u16 basic_exit_reason = exit_reason & VMX_BASIC_EXIT_REASON; > Just a naming suggestion: if we decide to go down this road, let's name it e.g. VMX_BASIC_EXIT_REASON_MASK to make it clear this is *not* an exit reason.
On 2/25/20 5:11 AM, Vitaly Kuznetsov wrote: > Krish Sadhukhan <krish.sadhukhan@oracle.com> writes: > >> We have a macro for bit 31, >> >> VMX_EXIT_REASONS_FAILED_VMENTRY 0x80000000 >> >> >> Does it make sense to define a macro like that instead ? Say, >> >> VMX_BASIC_EXIT_REASON 0x0000ffff >> > 0xffffU ? > >> and then we do, >> >> u32 exit_reason = vmx->exit_reason; >> u16 basic_exit_reason = exit_reason & VMX_BASIC_EXIT_REASON; >> > Just a naming suggestion: if we decide to go down this road, let's name > it e.g. VMX_BASIC_EXIT_REASON_MASK to make it clear this is *not* an > exit reason. > VMX_BASIC_EXIT_REASON_MASK works.
On Tue, Feb 25, 2020 at 02:41:20PM +0800, Xiaoyao Li wrote: > On 2/25/2020 2:13 PM, Sean Christopherson wrote: > >On Tue, Feb 25, 2020 at 08:13:15AM +0800, Xiaoyao Li wrote: > >>On 2/25/2020 12:17 AM, Sean Christopherson wrote: > >>I have thought about union, but it seems > >> > >>union { > >> u16 exit_reason; > >> u32 full_exit_reason; > >>} > >> > >>is not a good name. Since there are many codes in vmx.c and nested.c assume > >>that exit_reason stands for 32-bit EXIT REASON vmcs field as well as > >>evmcs->vm_exit_reason and vmcs12->vm_exit_reason. Do we really want to also > >>rename them to full_exit_reason? > > > >It's actually the opposite, almost all of the VMX code assumes exit_reason > >holds only the basic exit reason, i.e. a 16-bit value. For example, SGX > >adds a modifier flag to denote a VM-Exit was from enclave mode, and that > >bit needs to be stripped from exit_reason, otherwise all the checks like > >"if (exit_reason == blah_blah_blah)" fail. > > > >Making exit_reason a 16-bit alias of the full/extended exit_reason neatly > >sidesteps that issue. And it is an issue that has caused actual problems > >in the past, e.g. see commit beb8d93b3e42 ("KVM: VMX: Fix handling of #MC > >that occurs during VM-Entry"). Coincidentally, that commit also removes a > >local "u16 basic_exit_reason" :-). > > > >Except for one mistake, the pseudo-patch below is the entirety of required > >changes. Most (all?) of the functions that take "u32 exit_reason" can (and > >should) continue to take a u32. > > > >As for the name, I strongly prefer keeping the exit_reason name for the > >basic exit reason. The vast majority of VM-Exits do not have modifiers > >set, i.e. "basic exit reason" == vmcs.EXIT_REASON for nearly all normal > >usage. This holds true in every form of communication, e.g. when discussing > >VM-Exit reasons, it's never qualified with "basic", it's simply the exit > >reason. IMO the code is better off following the colloquial usage of "exit > >reason". A simple comment above the union would suffice to clear up any > >confusion with respect to the SDM. > > Well, for this reason we can keep exit_reason for 16-bit usage, and define > full/extended_exit_reason for 32-bit cases. This makes less code churn. > > But after we choose to use exit_reason and full/extended_exit_reason, what > if someday new modifier flags are added and we want to enable some modifier > flags for nested case? > I guess we need to change existing exit_reason to full/extended_exit_reason > in nested.c/nested.h to keep the naming rule consistent. Ah, good point. But, that's just another bug in my psuedo patch :-) It's literally one call site that needs to be updated. E.g. if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) return nested_vmx_reflect_vmexit(vcpu, full_exit_reason); Everywhere else KVM calls nested_vmx_reflect_vmexit() is (currently) done with a hardcoded value (except handle_vmfunc(), but I actually want to change that one).
On 2/27/2020 7:59 AM, Sean Christopherson wrote: > On Tue, Feb 25, 2020 at 02:41:20PM +0800, Xiaoyao Li wrote: >> On 2/25/2020 2:13 PM, Sean Christopherson wrote: >>> On Tue, Feb 25, 2020 at 08:13:15AM +0800, Xiaoyao Li wrote: >>>> On 2/25/2020 12:17 AM, Sean Christopherson wrote: >>>> I have thought about union, but it seems >>>> >>>> union { >>>> u16 exit_reason; >>>> u32 full_exit_reason; >>>> } >>>> >>>> is not a good name. Since there are many codes in vmx.c and nested.c assume >>>> that exit_reason stands for 32-bit EXIT REASON vmcs field as well as >>>> evmcs->vm_exit_reason and vmcs12->vm_exit_reason. Do we really want to also >>>> rename them to full_exit_reason? >>> >>> It's actually the opposite, almost all of the VMX code assumes exit_reason >>> holds only the basic exit reason, i.e. a 16-bit value. For example, SGX >>> adds a modifier flag to denote a VM-Exit was from enclave mode, and that >>> bit needs to be stripped from exit_reason, otherwise all the checks like >>> "if (exit_reason == blah_blah_blah)" fail. >>> >>> Making exit_reason a 16-bit alias of the full/extended exit_reason neatly >>> sidesteps that issue. And it is an issue that has caused actual problems >>> in the past, e.g. see commit beb8d93b3e42 ("KVM: VMX: Fix handling of #MC >>> that occurs during VM-Entry"). Coincidentally, that commit also removes a >>> local "u16 basic_exit_reason" :-). >>> >>> Except for one mistake, the pseudo-patch below is the entirety of required >>> changes. Most (all?) of the functions that take "u32 exit_reason" can (and >>> should) continue to take a u32. >>> >>> As for the name, I strongly prefer keeping the exit_reason name for the >>> basic exit reason. The vast majority of VM-Exits do not have modifiers >>> set, i.e. "basic exit reason" == vmcs.EXIT_REASON for nearly all normal >>> usage. This holds true in every form of communication, e.g. when discussing >>> VM-Exit reasons, it's never qualified with "basic", it's simply the exit >>> reason. IMO the code is better off following the colloquial usage of "exit >>> reason". A simple comment above the union would suffice to clear up any >>> confusion with respect to the SDM. >> >> Well, for this reason we can keep exit_reason for 16-bit usage, and define >> full/extended_exit_reason for 32-bit cases. This makes less code churn. >> >> But after we choose to use exit_reason and full/extended_exit_reason, what >> if someday new modifier flags are added and we want to enable some modifier >> flags for nested case? >> I guess we need to change existing exit_reason to full/extended_exit_reason >> in nested.c/nested.h to keep the naming rule consistent. > > Ah, good point. But, that's just another bug in my psuedo patch :-) > It's literally one call site that needs to be updated. E.g. > > if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) > return nested_vmx_reflect_vmexit(vcpu, full_exit_reason); > shouldn't we also pass full_exit_reason to nested_vmx_exit_reflected()? > Everywhere else KVM calls nested_vmx_reflect_vmexit() is (currently) done I guess you wanted to say nested_vmx_vmexit() not nested_vmx_reflect_vmexit() here. > with a hardcoded value (except handle_vmfunc(), but I actually want to > change that one). >
On Thu, Feb 27, 2020 at 04:35:20PM +0800, Xiaoyao Li wrote: > On 2/27/2020 7:59 AM, Sean Christopherson wrote: > >Ah, good point. But, that's just another bug in my psuedo patch :-) > >It's literally one call site that needs to be updated. E.g. > > > > if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason)) > > return nested_vmx_reflect_vmexit(vcpu, full_exit_reason); > > > > shouldn't we also pass full_exit_reason to nested_vmx_exit_reflected()? Yep, see the patch I sent. Alternatively, and perhaps a better approach once we have the union, would be to not pass exit_reason at all and instead have nested_vmx_exit_reflected() grab it directly from vmx->... > > >Everywhere else KVM calls nested_vmx_reflect_vmexit() is (currently) done > > I guess you wanted to say nested_vmx_vmexit() not > nested_vmx_reflect_vmexit() here. Ya. > >with a hardcoded value (except handle_vmfunc(), but I actually want to > >change that one). > > >
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 9a6664886f2e..85da72d4dc92 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1584,7 +1584,7 @@ static int skip_emulated_instruction(struct kvm_vcpu *vcpu) * i.e. we end up advancing IP with some random value. */ if (!static_cpu_has(X86_FEATURE_HYPERVISOR) || - to_vmx(vcpu)->exit_reason != EXIT_REASON_EPT_MISCONFIG) { + basic(to_vmx(vcpu)->exit_reason) != EXIT_REASON_EPT_MISCONFIG) { rip = kvm_rip_read(vcpu); rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN); kvm_rip_write(vcpu, rip); @@ -5797,6 +5797,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, { struct vcpu_vmx *vmx = to_vmx(vcpu); u32 exit_reason = vmx->exit_reason; + u16 basic_exit_reason = basic(exit_reason); u32 vectoring_info = vmx->idt_vectoring_info; trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX); @@ -5842,17 +5843,17 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, * will cause infinite loop. */ if ((vectoring_info & VECTORING_INFO_VALID_MASK) && - (exit_reason != EXIT_REASON_EXCEPTION_NMI && - exit_reason != EXIT_REASON_EPT_VIOLATION && - exit_reason != EXIT_REASON_PML_FULL && - exit_reason != EXIT_REASON_TASK_SWITCH)) { + (basic_exit_reason != EXIT_REASON_EXCEPTION_NMI && + basic_exit_reason != EXIT_REASON_EPT_VIOLATION && + basic_exit_reason != EXIT_REASON_PML_FULL && + basic_exit_reason != EXIT_REASON_TASK_SWITCH)) { vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_DELIVERY_EV; vcpu->run->internal.ndata = 3; vcpu->run->internal.data[0] = vectoring_info; vcpu->run->internal.data[1] = exit_reason; vcpu->run->internal.data[2] = vcpu->arch.exit_qualification; - if (exit_reason == EXIT_REASON_EPT_MISCONFIG) { + if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) { vcpu->run->internal.ndata++; vcpu->run->internal.data[3] = vmcs_read64(GUEST_PHYSICAL_ADDRESS); @@ -5884,32 +5885,32 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, return 1; } - if (exit_reason >= kvm_vmx_max_exit_handlers) + if (basic_exit_reason >= kvm_vmx_max_exit_handlers) goto unexpected_vmexit; #ifdef CONFIG_RETPOLINE - if (exit_reason == EXIT_REASON_MSR_WRITE) + if (basic_exit_reason == EXIT_REASON_MSR_WRITE) return kvm_emulate_wrmsr(vcpu); - else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER) + else if (basic_exit_reason == EXIT_REASON_PREEMPTION_TIMER) return handle_preemption_timer(vcpu); - else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW) + else if (basic_exit_reason == EXIT_REASON_INTERRUPT_WINDOW) return handle_interrupt_window(vcpu); - else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) + else if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) return handle_external_interrupt(vcpu); - else if (exit_reason == EXIT_REASON_HLT) + else if (basic_exit_reason == EXIT_REASON_HLT) return kvm_emulate_halt(vcpu); - else if (exit_reason == EXIT_REASON_EPT_MISCONFIG) + else if (basic_exit_reason == EXIT_REASON_EPT_MISCONFIG) return handle_ept_misconfig(vcpu); #endif - exit_reason = array_index_nospec(exit_reason, + basic_exit_reason = array_index_nospec(basic_exit_reason, kvm_vmx_max_exit_handlers); - if (!kvm_vmx_exit_handlers[exit_reason]) + if (!kvm_vmx_exit_handlers[basic_exit_reason]) goto unexpected_vmexit; - return kvm_vmx_exit_handlers[exit_reason](vcpu); + return kvm_vmx_exit_handlers[basic_exit_reason](vcpu); unexpected_vmexit: - vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason); + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", basic_exit_reason); dump_vmcs(); vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; vcpu->run->internal.suberror = @@ -6241,13 +6242,14 @@ static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu, enum exit_fastpath_completion *exit_fastpath) { struct vcpu_vmx *vmx = to_vmx(vcpu); + u16 basic_exit_reason = basic(vmx->exit_reason); - if (vmx->exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) + if (basic_exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) handle_external_interrupt_irqoff(vcpu); - else if (vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI) + else if (basic_exit_reason == EXIT_REASON_EXCEPTION_NMI) handle_exception_nmi_irqoff(vmx); else if (!is_guest_mode(vcpu) && - vmx->exit_reason == EXIT_REASON_MSR_WRITE) + basic_exit_reason == EXIT_REASON_MSR_WRITE) *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu); } @@ -6621,7 +6623,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) vmx->idt_vectoring_info = 0; vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON); - if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY) + if (basic(vmx->exit_reason) == EXIT_REASON_MCE_DURING_VMENTRY) kvm_machine_check(); if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 7f42cf3dcd70..c6ba33eedb59 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -22,6 +22,8 @@ extern u32 get_umwait_control_msr(void); #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4)) +#define basic(exit_reason) ((u16)(exit_reason)) + #ifdef CONFIG_X86_64 #define NR_SHARED_MSRS 7 #else
Current kvm uses the 32-bit exit reason to check if it's any specific VM EXIT, however only the low 16-bit of VM EXIT REASON acts as the basic exit reason. Introduce Macro basic(exit_reaso) to help retrieve the basic exit reason from VM EXIT REASON, and use the basic exit reason for checking and indexing the exit hanlder. Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> --- arch/x86/kvm/vmx/vmx.c | 44 ++++++++++++++++++++++-------------------- arch/x86/kvm/vmx/vmx.h | 2 ++ 2 files changed, 25 insertions(+), 21 deletions(-)