On Thu, Jun 30, 2022, Jim Mattson wrote: > 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. The shortlog and this sentence need to be updated, the stuffing code is still in-line, but the JMP is being dropped. > 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 >
