On 30/07/2018 21:40, Matthew Whitehead wrote: > early_init_amd() is called on all AMD processors, both 64 and 32 bit. > Presently 32 bit processors get the X86_FEATURE_VMMCALL feature set, which > they do not support. Add conditionals to restrict it to 64 bit processors.
This shouldn't be necessary; for systems that don't have virtualization extensions, the comment explains why setting X86_FEATURE_VMMCALL is safe. But it is also wrong, because you can run a 32-bit kernel as a guest on a 64-bit processor, and then it should set X86_FEATURE_VMMCALL because the processor has the vmmcall instruction and not Intel's vmcall. Thanks, Paolo > Cc: Paolo Bonzini <pbonz...@redhat.com> > Signed-off-by: Matthew Whitehead <tedheads...@gmail.com> > --- > arch/x86/kernel/cpu/amd.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c > index 38915fbfae73..df06919324cd 100644 > --- a/arch/x86/kernel/cpu/amd.c > +++ b/arch/x86/kernel/cpu/amd.c > @@ -662,12 +662,14 @@ static void early_init_amd(struct cpuinfo_x86 *c) > } > #endif > > +#ifdef CONFIG_X86_64 > /* > * This is only needed to tell the kernel whether to use VMCALL > * and VMMCALL. VMMCALL is never executed except under virt, so > * we can set it unconditionally. > */ > set_cpu_cap(c, X86_FEATURE_VMMCALL); > +#endif > > /* F16h erratum 793, CVE-2013-6885 */ > if (c->x86 == 0x16 && c->x86_model <= 0xf) >
