| Message ID | 1500507602-105830-1-git-send-email-wanpeng.li@hotmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
2017-07-19 16:40-0700, Wanpeng Li: > From: Wanpeng Li <wanpeng.li@hotmail.com> > > This can be reproduced by EPT=1, unrestricted_guest=N, emulate_invalid_state=Y > or EPT=0, the trace of kvm-unit-tests/taskswitch2.flat is like below, it tries > to emulate invalid guest state task-switch: > > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > kvm_entry: vcpu 0 > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > ...................... > > It appears that the task-switch emulation updates rflags (and vm86 > flag) only after the segments are loaded, causing vmx->emulation_required > to be set, when in fact invalid guest state emulation is not needed. > > This patch fixes it by updating vmx->emulation_required after the > rflags (and vm86 flag) is updated in task-switch emulation. > > Thanks Radim for moving the update to vmx__set_flags and adding Paolo's > suggestion for the check. > > Suggested-by: Nadav Amit <nadav.amit@gmail.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: Nadav Amit <nadav.amit@gmail.com> > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> > --- > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > { > + unsigned long old_rflags = vmx_get_rflags(vcpu); > + unsigned long save_rflags = rflags; > + > __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); > to_vmx(vcpu)->rflags = rflags; > if (to_vmx(vcpu)->rmode.vm86_active) { > @@ -2370,6 +2378,9 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; > } > vmcs_writel(GUEST_RFLAGS, rflags); > + > + if ((old_rflags ^ save_rflags) & X86_EFLAGS_VM) Looks good, thanks to both. The desired rflags are saved in to_vmx(vcpu)->rflags, so we don't need the temporary variable -- would using that or vmx_get_rflags(vcpu) generate worse code?
2017-07-20 15:57 GMT+08:00 Radim Krčmář <rkrcmar@redhat.com>: > 2017-07-19 16:40-0700, Wanpeng Li: >> From: Wanpeng Li <wanpeng.li@hotmail.com> >> >> This can be reproduced by EPT=1, unrestricted_guest=N, emulate_invalid_state=Y >> or EPT=0, the trace of kvm-unit-tests/taskswitch2.flat is like below, it tries >> to emulate invalid guest state task-switch: >> >> kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 >> kvm_emulate_insn: 42000:0:0f 0b (0x2) >> kvm_emulate_insn: 42000:0:0f 0b (0x2) failed >> kvm_inj_exception: #UD (0x0) >> kvm_entry: vcpu 0 >> kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 >> kvm_emulate_insn: 42000:0:0f 0b (0x2) >> kvm_emulate_insn: 42000:0:0f 0b (0x2) failed >> kvm_inj_exception: #UD (0x0) >> ...................... >> >> It appears that the task-switch emulation updates rflags (and vm86 >> flag) only after the segments are loaded, causing vmx->emulation_required >> to be set, when in fact invalid guest state emulation is not needed. >> >> This patch fixes it by updating vmx->emulation_required after the >> rflags (and vm86 flag) is updated in task-switch emulation. >> >> Thanks Radim for moving the update to vmx__set_flags and adding Paolo's >> suggestion for the check. >> >> Suggested-by: Nadav Amit <nadav.amit@gmail.com> >> Cc: Paolo Bonzini <pbonzini@redhat.com> >> Cc: Radim Krčmář <rkrcmar@redhat.com> >> Cc: Nadav Amit <nadav.amit@gmail.com> >> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> >> --- >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) >> { >> + unsigned long old_rflags = vmx_get_rflags(vcpu); >> + unsigned long save_rflags = rflags; >> + >> __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); >> to_vmx(vcpu)->rflags = rflags; >> if (to_vmx(vcpu)->rmode.vm86_active) { >> @@ -2370,6 +2378,9 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) >> rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; >> } >> vmcs_writel(GUEST_RFLAGS, rflags); >> + >> + if ((old_rflags ^ save_rflags) & X86_EFLAGS_VM) > > Looks good, thanks to both. > > The desired rflags are saved in to_vmx(vcpu)->rflags, so we don't need > the temporary variable -- would using that or vmx_get_rflags(vcpu) > generate worse code? Yeah, I will send out a newer version. Regards, Wanpeng Li
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 84e62ac..287639e 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2326,6 +2326,11 @@ static void vmx_vcpu_put(struct kvm_vcpu *vcpu) __vmx_load_host_state(to_vmx(vcpu)); } +static bool emulation_required(struct kvm_vcpu *vcpu) +{ + return emulate_invalid_guest_state && !guest_state_valid(vcpu); +} + static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu); /* @@ -2363,6 +2368,9 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) { + unsigned long old_rflags = vmx_get_rflags(vcpu); + unsigned long save_rflags = rflags; + __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); to_vmx(vcpu)->rflags = rflags; if (to_vmx(vcpu)->rmode.vm86_active) { @@ -2370,6 +2378,9 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; } vmcs_writel(GUEST_RFLAGS, rflags); + + if ((old_rflags ^ save_rflags) & X86_EFLAGS_VM) + to_vmx(vcpu)->emulation_required = emulation_required(vcpu); } static u32 vmx_get_pkru(struct kvm_vcpu *vcpu) @@ -3857,11 +3868,6 @@ static __init int alloc_kvm_area(void) return 0; } -static bool emulation_required(struct kvm_vcpu *vcpu) -{ - return emulate_invalid_guest_state && !guest_state_valid(vcpu); -} - static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg, struct kvm_segment *save) {