diff options
| author | Sean Christopherson <seanjc@google.com> | 2025-11-18 14:23:25 -0800 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-11-18 16:22:46 -0800 |
| commit | ebd1a336550096bf7543699bab2e89fa401deac6 (patch) | |
| tree | 9bb58894369d91a850eecfb908a83bbc127884ef /arch/x86/kvm/svm/svm.c | |
| parent | 38ee66cb1845dbf1e97c5e5d3db01ae4513f66a9 (diff) | |
KVM: SVM: Handle #MCs in guest outside of fastpath
Handle Machine Checks (#MC) that happen in the guest (by forwarding them
to the host) outside of KVM's fastpath so that as much host state as
possible is re-loaded before invoking the kernel's #MC handler. The only
requirement is that KVM invokes the #MC handler before enabling IRQs (and
even that could _probably_ be relaxed to handling #MCs before enabling
preemption).
Waiting to handle #MCs until "more" host state is loaded hardens KVM
against flaws in the #MC handler, which has historically been quite
brittle. E.g. prior to commit 5567d11c21a1 ("x86/mce: Send #MC singal from
task work"), the #MC code could trigger a schedule() with IRQs and
preemption disabled. That led to a KVM hack-a-fix in commit 1811d979c716
("x86/kvm: move kvm_load/put_guest_xcr0 into atomic context").
Note, except for #MCs on VM-Enter, VMX already handles #MCs outside of the
fastpath.
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Jon Kohler <jon@nutanix.com>
Link: https://patch.msgid.link/20251118222328.2265758-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/svm/svm.c')
| -rw-r--r-- | arch/x86/kvm/svm/svm.c | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 59d896322855..ff6ddba16a26 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4325,14 +4325,6 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags) vcpu->arch.regs_avail &= ~SVM_REGS_LAZY_LOAD_SET; - /* - * We need to handle MC intercepts here before the vcpu has a chance to - * change the physical cpu - */ - if (unlikely(svm->vmcb->control.exit_code == - SVM_EXIT_EXCP_BASE + MC_VECTOR)) - svm_handle_mce(vcpu); - trace_kvm_exit(vcpu, KVM_ISA_SVM); svm_complete_interrupts(vcpu); @@ -4621,8 +4613,16 @@ out: static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu) { - if (to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_INTR) + switch (to_svm(vcpu)->vmcb->control.exit_code) { + case SVM_EXIT_EXCP_BASE + MC_VECTOR: + svm_handle_mce(vcpu); + break; + case SVM_EXIT_INTR: vcpu->arch.at_instruction_boundary = true; + break; + default: + break; + } } static void svm_setup_mce(struct kvm_vcpu *vcpu) |