On Wed, May 24, 2023 at 05:24:23PM +0000, Edgecombe, Rick P wrote: > On Wed, 2023-05-24 at 15:53 +0000, John Allen wrote: > > If the CPU supports CET, add CET XSAVES feature bits to the > > supported_xss mask. > > > > Signed-off-by: John Allen <john.allen@xxxxxxx> > > --- > > v2: > > - Remove curly braces around if statement > > --- > > arch/x86/kvm/svm/svm.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > > index 6afd2c44fdb6..cee496bee0a9 100644 > > --- a/arch/x86/kvm/svm/svm.c > > +++ b/arch/x86/kvm/svm/svm.c > > @@ -5070,6 +5070,10 @@ static __init void svm_set_cpu_caps(void) > > boot_cpu_has(X86_FEATURE_AMD_SSBD)) > > kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD); > > > > + if (kvm_cpu_cap_has(X86_FEATURE_SHSTK)) > > + kvm_caps.supported_xss |= XFEATURE_MASK_CET_USER | > > + XFEATURE_MASK_CET_KERNEL; > > + > > Is setting XFEATURE_MASK_CET_KERNEL here ok? The host kernel will not > support XFEATURE_MASK_CET_KERNEL. I guess after this there is a small > window of time where host IA32_XSS could have non-host supported > supervisor state. > > Sort of separately, how does SVM work with respect to saving and > restoring guest supervisor CET state (I mean the CET_S stuff)? Apart from a minor exception involving SEV-ES, we are piggybacking on the state saving/restoring in Yang Weijiang's x86/VMX series. So by inspection, it looks like guest supervisor support is broken as the supervisor XSAVES state and MSRs are not included in that series. I currently don't have a way to test this case, but I think there are operating systems that support it. I'll work on getting a guest set up that can actually test this and hopefully have working guest supervisor support in the next version of the series. Thanks, John > > I'm not sure there is any problem, but just wondering how it all works. > Thanks.
