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| author | Sean Christopherson <seanjc@google.com> | 2023-07-21 23:18:59 +0300 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-08-04 01:37:15 +0300 |
| commit | a788fbb763b5001f67f2ecdf207a357f9b12838f (patch) | |
| tree | 7574d983e07db0cd9b8fab1dcb88a2c97661157b | |
| parent | 2e6b9bd49b702c4a52278e35202354b709021116 (diff) | |
| download | linux-a788fbb763b5001f67f2ecdf207a357f9b12838f.tar.xz | |
KVM: VMX: Skip VMCLEAR logic during emergency reboots if CR4.VMXE=0
Bail from vmx_emergency_disable() without processing the list of loaded
VMCSes if CR4.VMXE=0, i.e. if the CPU can't be post-VMXON. It should be
impossible for the list to have entries if VMX is already disabled, and
even if that invariant doesn't hold, VMCLEAR will #UD anyways, i.e.
processing the list is pointless even if it somehow isn't empty.
Assuming no existing KVM bugs, this should be a glorified nop. The
primary motivation for the change is to avoid having code that looks like
it does VMCLEAR, but then skips VMXON, which is nonsensical.
Suggested-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-20-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 415665c40a39..83338872a39f 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -754,12 +754,20 @@ static void vmx_emergency_disable(void) kvm_rebooting = true; + /* + * Note, CR4.VMXE can be _cleared_ in NMI context, but it can only be + * set in task context. If this races with VMX is disabled by an NMI, + * VMCLEAR and VMXOFF may #UD, but KVM will eat those faults due to + * kvm_rebooting set. + */ + if (!(__read_cr4() & X86_CR4_VMXE)) + return; + list_for_each_entry(v, &per_cpu(loaded_vmcss_on_cpu, cpu), loaded_vmcss_on_cpu_link) vmcs_clear(v->vmcs); - if (__read_cr4() & X86_CR4_VMXE) - kvm_cpu_vmxoff(); + kvm_cpu_vmxoff(); } static void __loaded_vmcs_clear(void *arg) |