| Message ID | 20221130230934.1014142-41-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Rework kvm_init() and hardware enabling | expand |
On Wed, 2022-11-30 at 23:09 +0000, Sean Christopherson wrote: > From: Chao Gao <chao.gao@intel.com> > > Do compatibility checks when enabling hardware to effectively add > compatibility checks when onlining a CPU. Abort enabling, i.e. the > online process, if the (hotplugged) CPU is incompatible with the known > good setup. > > At init time, KVM does compatibility checks to ensure that all online > CPUs support hardware virtualization and a common set of features. But > KVM uses hotplugged CPUs without such compatibility checks. On Intel > CPUs, this leads to #GP if the hotplugged CPU doesn't support VMX, or > VM-Entry failure if the hotplugged CPU doesn't support all features > enabled by KVM. > > Note, this is little more than a NOP on SVM, as SVM already checks for > full SVM support during hardware enabling. > > Opportunistically add a pr_err() if setup_vmcs_config() fails, and > tweak all error messages to output which CPU failed. > > Signed-off-by: Chao Gao <chao.gao@intel.com> > Co-developed-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> For VMX: Acked-by: Kai Huang <kai.huang@intel.com> > --- > arch/x86/kvm/svm/svm.c | 8 +++----- > arch/x86/kvm/vmx/vmx.c | 15 ++++++++++----- > arch/x86/kvm/x86.c | 5 +++++ > 3 files changed, 18 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index c2e95c0d9fd8..46b658d0f46e 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -521,11 +521,12 @@ static void svm_init_osvw(struct kvm_vcpu *vcpu) > > static bool kvm_is_svm_supported(void) > { > + int cpu = raw_smp_processor_id(); > const char *msg; > u64 vm_cr; > > if (!cpu_has_svm(&msg)) { > - pr_err("SVM not supported, %s\n", msg); > + pr_err("SVM not supported by CPU %d, %s\n", cpu, msg); > return false; > } > > @@ -536,7 +537,7 @@ static bool kvm_is_svm_supported(void) > > rdmsrl(MSR_VM_CR, vm_cr); > if (vm_cr & (1 << SVM_VM_CR_SVM_DISABLE)) { > - pr_err("SVM disabled (by BIOS) in MSR_VM_CR\n"); > + pr_err("SVM disabled (by BIOS) in MSR_VM_CR on CPU %d\n", cpu); > return false; > } > > @@ -587,9 +588,6 @@ static int svm_hardware_enable(void) > if (efer & EFER_SVME) > return -EBUSY; > > - if (!kvm_is_svm_supported()) > - return -EINVAL; > - > sd = per_cpu_ptr(&svm_data, me); > sd->asid_generation = 1; > sd->max_asid = cpuid_ebx(SVM_CPUID_FUNC) - 1; > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 6416ed5b7f89..39dd3082fcd8 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -2711,14 +2711,16 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf, > > static bool kvm_is_vmx_supported(void) > { > + int cpu = raw_smp_processor_id(); > + > if (!cpu_has_vmx()) { > - pr_err("CPU doesn't support VMX\n"); > + pr_err("VMX not supported by CPU %d\n", cpu); > return false; > } > > if (!this_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || > !this_cpu_has(X86_FEATURE_VMX)) { > - pr_err("VMX not enabled (by BIOS) in MSR_IA32_FEAT_CTL\n"); > + pr_err("VMX not enabled (by BIOS) in MSR_IA32_FEAT_CTL on CPU %d\n", cpu); > return false; > } > > @@ -2727,18 +2729,21 @@ static bool kvm_is_vmx_supported(void) > > static int vmx_check_processor_compat(void) > { > + int cpu = raw_smp_processor_id(); > struct vmcs_config vmcs_conf; > struct vmx_capability vmx_cap; > > if (!kvm_is_vmx_supported()) > return -EIO; > > - if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0) > + if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0) { > + pr_err("Failed to setup VMCS config on CPU %d\n", cpu); > return -EIO; > + } > if (nested) > nested_vmx_setup_ctls_msrs(&vmcs_conf, vmx_cap.ept); > - if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config)) != 0) { > - pr_err("CPU %d feature inconsistency!\n", smp_processor_id()); > + if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config))) { > + pr_err("Inconsistent VMCS config on CPU %d\n", cpu); > return -EIO; > } > return 0; > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index ee9af412ffd4..5a9e74cedbc6 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11967,6 +11967,11 @@ int kvm_arch_hardware_enable(void) > bool stable, backwards_tsc = false; > > kvm_user_return_msr_cpu_online(); > + > + ret = kvm_x86_check_processor_compatibility(); > + if (ret) > + return ret; > + > ret = static_call(kvm_x86_hardware_enable)(); > if (ret != 0) > return ret;
On Wed, 2022-11-30 at 23:09 +0000, Sean Christopherson wrote: > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11967,6 +11967,11 @@ int kvm_arch_hardware_enable(void) > bool stable, backwards_tsc = false; > > kvm_user_return_msr_cpu_online(); > + > + ret = kvm_x86_check_processor_compatibility(); > + if (ret) > + return ret; > + > ret = static_call(kvm_x86_hardware_enable)(); > if (ret != 0) > return ret; Thinking more, AFAICT, kvm_x86_vendor_init() so far still does the compatibility check on all online cpus. Since now kvm_arch_hardware_enable() also does the compatibility check, IIUC the compatibility check will be done twice -- one in kvm_x86_vendor_init() and one in hardware_enable_all() when creating the first VM. Do you think it's still worth to do compatibility check in vm_x86_vendor_init()? The behaviour difference should be "KVM module fail to load" vs "failing to create the first VM" IIUC. I don't know whether the former is better than the better, but it seems duplicated compatibility checking isn't needed?
On Fri, Dec 02, 2022, Huang, Kai wrote: > On Wed, 2022-11-30 at 23:09 +0000, Sean Christopherson wrote: > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -11967,6 +11967,11 @@ int kvm_arch_hardware_enable(void) > > bool stable, backwards_tsc = false; > > > > kvm_user_return_msr_cpu_online(); > > + > > + ret = kvm_x86_check_processor_compatibility(); > > + if (ret) > > + return ret; > > + > > ret = static_call(kvm_x86_hardware_enable)(); > > if (ret != 0) > > return ret; > > Thinking more, AFAICT, kvm_x86_vendor_init() so far still does the compatibility > check on all online cpus. Since now kvm_arch_hardware_enable() also does the > compatibility check, IIUC the compatibility check will be done twice -- one in > kvm_x86_vendor_init() and one in hardware_enable_all() when creating the first > VM. > > Do you think it's still worth to do compatibility check in vm_x86_vendor_init()? > > The behaviour difference should be "KVM module fail to load" vs "failing to > create the first VM" IIUC. I don't know whether the former is better than the > better, but it seems duplicated compatibility checking isn't needed? It's not strictly needed, but I think it's worth keeping. The duplicate checking annoys me too, and I considered removing it multiple times when creating this series. But, if there is a hardware incompatibility for whatever reason, failing to load and thus not instantiating /dev/kvm is friendlier to userspace, e.g. userspace can immediately flag the platform as potentially flaky, whereas detecting the likely hardware issue when VM creation fails would essentialy require scraping the kernel logs.
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index c2e95c0d9fd8..46b658d0f46e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -521,11 +521,12 @@ static void svm_init_osvw(struct kvm_vcpu *vcpu) static bool kvm_is_svm_supported(void) { + int cpu = raw_smp_processor_id(); const char *msg; u64 vm_cr; if (!cpu_has_svm(&msg)) { - pr_err("SVM not supported, %s\n", msg); + pr_err("SVM not supported by CPU %d, %s\n", cpu, msg); return false; } @@ -536,7 +537,7 @@ static bool kvm_is_svm_supported(void) rdmsrl(MSR_VM_CR, vm_cr); if (vm_cr & (1 << SVM_VM_CR_SVM_DISABLE)) { - pr_err("SVM disabled (by BIOS) in MSR_VM_CR\n"); + pr_err("SVM disabled (by BIOS) in MSR_VM_CR on CPU %d\n", cpu); return false; } @@ -587,9 +588,6 @@ static int svm_hardware_enable(void) if (efer & EFER_SVME) return -EBUSY; - if (!kvm_is_svm_supported()) - return -EINVAL; - sd = per_cpu_ptr(&svm_data, me); sd->asid_generation = 1; sd->max_asid = cpuid_ebx(SVM_CPUID_FUNC) - 1; diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 6416ed5b7f89..39dd3082fcd8 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2711,14 +2711,16 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf, static bool kvm_is_vmx_supported(void) { + int cpu = raw_smp_processor_id(); + if (!cpu_has_vmx()) { - pr_err("CPU doesn't support VMX\n"); + pr_err("VMX not supported by CPU %d\n", cpu); return false; } if (!this_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || !this_cpu_has(X86_FEATURE_VMX)) { - pr_err("VMX not enabled (by BIOS) in MSR_IA32_FEAT_CTL\n"); + pr_err("VMX not enabled (by BIOS) in MSR_IA32_FEAT_CTL on CPU %d\n", cpu); return false; } @@ -2727,18 +2729,21 @@ static bool kvm_is_vmx_supported(void) static int vmx_check_processor_compat(void) { + int cpu = raw_smp_processor_id(); struct vmcs_config vmcs_conf; struct vmx_capability vmx_cap; if (!kvm_is_vmx_supported()) return -EIO; - if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0) + if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0) { + pr_err("Failed to setup VMCS config on CPU %d\n", cpu); return -EIO; + } if (nested) nested_vmx_setup_ctls_msrs(&vmcs_conf, vmx_cap.ept); - if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config)) != 0) { - pr_err("CPU %d feature inconsistency!\n", smp_processor_id()); + if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config))) { + pr_err("Inconsistent VMCS config on CPU %d\n", cpu); return -EIO; } return 0; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ee9af412ffd4..5a9e74cedbc6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11967,6 +11967,11 @@ int kvm_arch_hardware_enable(void) bool stable, backwards_tsc = false; kvm_user_return_msr_cpu_online(); + + ret = kvm_x86_check_processor_compatibility(); + if (ret) + return ret; + ret = static_call(kvm_x86_hardware_enable)(); if (ret != 0) return ret;