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| author |   Sean Christopherson <seanjc@google.com> | 2024-12-20 17:16:47 -0800 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-01-08 14:08:25 -0800 |
| commit | 4c20cd4cee929aef89118ac8820cefab427c6ae1 (patch) | |
| tree | b5a42f0bf35bf9e7d428a58d0e6c69c7fbc66f32 | |
| parent | KVM: x86: Use LVT_TIMER instead of an open coded literal (diff) | |
| download | wireguard-linux-4c20cd4cee929aef89118ac8820cefab427c6ae1.tar.xz wireguard-linux-4c20cd4cee929aef89118ac8820cefab427c6ae1.zip | |
KVM: x86: Avoid double RDPKRU when loading host/guest PKRU
Use the raw wrpkru() helper when loading the guest/host's PKRU on switch
to/from guest context, as the write_pkru() wrapper incurs an unnecessary
rdpkru(). In both paths, KVM is guaranteed to have performed RDPKRU since
the last possible write, i.e. KVM has a fresh cache of the current value
in hardware.
This effectively restores KVM's behavior to that of KVM prior to commit
c806e88734b9 ("x86/pkeys: Provide *pkru() helpers"), which renamed the raw
helper from __write_pkru() => wrpkru(), and turned __write_pkru() into a
wrapper. Commit 577ff465f5a6 ("x86/fpu: Only write PKRU if it is different
from current") then added the extra RDPKRU to avoid an unnecessary WRPKRU,
but completely missed that KVM already optimized away pointless writes.
Reported-by: Adrian Hunter <adrian.hunter@intel.com>
Fixes: 577ff465f5a6 ("x86/fpu: Only write PKRU if it is different from current")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20241221011647.3747448-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kvm/x86.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7bbdf916a136..46d12128f032 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1186,7 +1186,7 @@ void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu) vcpu->arch.pkru != vcpu->arch.host_pkru && ((vcpu->arch.xcr0 & XFEATURE_MASK_PKRU) || kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE))) - write_pkru(vcpu->arch.pkru); + wrpkru(vcpu->arch.pkru); } EXPORT_SYMBOL_GPL(kvm_load_guest_xsave_state); @@ -1200,7 +1200,7 @@ void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu) kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE))) { vcpu->arch.pkru = rdpkru(); if (vcpu->arch.pkru != vcpu->arch.host_pkru) - write_pkru(vcpu->arch.host_pkru); + wrpkru(vcpu->arch.host_pkru); } if (kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE)) { |