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| author | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-07 11:14:27 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-09 18:25:06 +0100 |
| commit | e61ab42de874c5af8c5d98b327c77a374d9e7da1 (patch) | |
| tree | 19fc4417cd0b452e2f8fe523495b5b36025ede22 /arch/x86/kvm/kvm-asm-offsets.c | |
| parent | KVM: SVM: do not allocate struct svm_cpu_data dynamically (diff) | |
| download | linux-e61ab42de874c5af8c5d98b327c77a374d9e7da1.tar.xz linux-e61ab42de874c5af8c5d98b327c77a374d9e7da1.zip | |
KVM: SVM: move guest vmsave/vmload back to assembly
It is error-prone that code after vmexit cannot access percpu data
because GSBASE has not been restored yet. It forces MSR_IA32_SPEC_CTRL
save/restore to happen very late, after the predictor untraining
sequence, and it gets in the way of return stack depth tracking
(a retbleed mitigation that is in linux-next as of 2022-11-09).
As a first step towards fixing that, move the VMCB VMSAVE/VMLOAD to
assembly, essentially undoing commit fb0c4a4fee5a ("KVM: SVM: move
VMLOAD/VMSAVE to C code", 2021-03-15). The reason for that commit was
that it made it simpler to use a different VMCB for VMLOAD/VMSAVE versus
VMRUN; but that is not a big hassle anymore thanks to the kvm-asm-offsets
machinery and other related cleanups.
The idea on how to number the exception tables is stolen from
a prototype patch by Peter Zijlstra.
Cc: stable@vger.kernel.org
Fixes: a149180fbcf3 ("x86: Add magic AMD return-thunk")
Link: <https://lore.kernel.org/all/f571e404-e625-bae1-10e9-449b2eb4cbd8@citrix.com/>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/kvm-asm-offsets.c')
| -rw-r--r-- | arch/x86/kvm/kvm-asm-offsets.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kvm/kvm-asm-offsets.c b/arch/x86/kvm/kvm-asm-offsets.c index f1b694e431ae..f83e88b85bf2 100644 --- a/arch/x86/kvm/kvm-asm-offsets.c +++ b/arch/x86/kvm/kvm-asm-offsets.c @@ -16,6 +16,7 @@ static void __used common(void) BLANK(); OFFSET(SVM_vcpu_arch_regs, vcpu_svm, vcpu.arch.regs); OFFSET(SVM_current_vmcb, vcpu_svm, current_vmcb); + OFFSET(SVM_vmcb01, vcpu_svm, vmcb01); OFFSET(KVM_VMCB_pa, kvm_vmcb_info, pa); } |