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| author | Sean Christopherson <seanjc@google.com> | 2023-03-22 04:14:39 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2023-04-06 20:37:37 +0300 |
| commit | da3db168fb671f15e393b227f5c312c698ecb6ea (patch) | |
| tree | 2abbafa3ebb3b959eb21757e891c92017265ceef /arch/x86/kvm/x86.c | |
| parent | 903358c7eddb9a8a83013f967909805e6af050d4 (diff) | |
| download | linux-da3db168fb671f15e393b227f5c312c698ecb6ea.tar.xz | |
KVM: x86: Virtualize FLUSH_L1D and passthrough MSR_IA32_FLUSH_CMD
Virtualize FLUSH_L1D so that the guest can use the performant L1D flush
if one of the many mitigations might require a flush in the guest, e.g.
Linux provides an option to flush the L1D when switching mms.
Passthrough MSR_IA32_FLUSH_CMD for write when it's supported in hardware
and exposed to the guest, i.e. always let the guest write it directly if
FLUSH_L1D is fully supported.
Forward writes to hardware in host context on the off chance that KVM
ends up emulating a WRMSR, or in the really unlikely scenario where
userspace wants to force a flush. Restrict these forwarded WRMSRs to
the known command out of an abundance of caution. Passing through the
MSR means the guest can throw any and all values at hardware, but doing
so in host context is arguably a bit more dangerous.
Link: https://lkml.kernel.org/r/CALMp9eTt3xzAEoQ038bJQ9LN0ZOXrSWsN7xnNUD%2B0SS%3DWwF7Pg%40mail.gmail.com
Link: https://lore.kernel.org/all/20230201132905.549148-2-eesposit@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230322011440.2195485-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c83ec88da043..3c58dbae7b4c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3628,6 +3628,18 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB); break; + case MSR_IA32_FLUSH_CMD: + if (!msr_info->host_initiated && + !guest_cpuid_has(vcpu, X86_FEATURE_FLUSH_L1D)) + return 1; + + if (!boot_cpu_has(X86_FEATURE_FLUSH_L1D) || (data & ~L1D_FLUSH)) + return 1; + if (!data) + break; + + wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH); + break; case MSR_EFER: return set_efer(vcpu, msr_info); case MSR_K7_HWCR: |