On 09/10/19 19:05, Sasha Levin wrote: > From: Sebastian Andrzej Siewior <[email protected]> > > [ Upstream commit 504ce1954fba888936c9d13ccc1e3db9b8f613d5 ] > > I was surprised to see that the guest reported `fxsave_leak' while the > host did not. After digging deeper I noticed that the bits are simply > masked out during enumeration. > > The XSAVEERPTR feature is actually a bug fix on AMD which means the > kernel can disable a workaround. > > Pass XSAVEERPTR to the guest if available on the host. > > Signed-off-by: Sebastian Andrzej Siewior <[email protected]> > Signed-off-by: Paolo Bonzini <[email protected]> > Signed-off-by: Sasha Levin <[email protected]> > --- > arch/x86/kvm/cpuid.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index fd1b8db8bf242..59b66e343fa5a 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -479,6 +479,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 > *entry, u32 function, > > /* cpuid 0x80000008.ebx */ > const u32 kvm_cpuid_8000_0008_ebx_x86_features = > + F(XSAVEERPTR) | > F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | > F(VIRT_SSBD) | > F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON); > >
Yet another example of a patch that shouldn't be stable material (in this case it's fine, but there can certainly be cases where just adding a single flag depends on core kernel changes). Paolo
