RSB-stuffing after VM-exit is only needed for legacy CPUs without eIBRS. Move the RSB-stuffing code out of line to avoid the JMP on modern CPUs. Note that CPUs that are subject to SpectreRSB attacks need RSB-stuffing on VM-exit whether or not RETPOLINE is in use as a SpectreBTB mitigation. However, I am leaving the existing mitigation strategy alone. Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx> --- arch/x86/kvm/vmx/vmenter.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index 435c187927c4..ea5986b96004 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -76,7 +76,8 @@ SYM_FUNC_END(vmx_vmenter) */ SYM_FUNC_START(vmx_vmexit) #ifdef CONFIG_RETPOLINE - ALTERNATIVE "jmp .Lvmexit_skip_rsb", "", X86_FEATURE_RETPOLINE + ALTERNATIVE "RET", "", X86_FEATURE_RETPOLINE + /* Preserve guest's RAX, it's used to stuff the RSB. */ push %_ASM_AX @@ -87,7 +88,6 @@ SYM_FUNC_START(vmx_vmexit) or $1, %_ASM_AX pop %_ASM_AX -.Lvmexit_skip_rsb: #endif RET SYM_FUNC_END(vmx_vmexit) -- 2.37.0.rc0.161.g10f37bed90-goog
