On 8/20/20 3:07 PM, Dave Hansen wrote:
On 8/20/20 12:05 PM, Tom Lendacky wrote:
I added a quick hack to save TSC_AUX to a new variable in the SVM
struct and then restore it right after VMEXIT (just after where GS is
restored in svm_vcpu_enter_exit()) and my guest is no longer crashing.
Sorry, I mean my host is no longer crashing.
Just to make sure I've got this:
1. Older CPUs didn't have X86_FEATURE_RDPID
2. FSGSBASE patches started using RDPID in the NMI entry path when
supported *AND* FSGSBASE was enabled
3. There was a latent SVM bug which did not restore the RDPID data
before NMIs were reenabled after VMEXIT
4. If an NMI comes in the window between VMEXIT and the
wrmsr(TSC_AUX)... boom
Right, which means that the setting of TSC_AUX to the guest value needs to
be moved, too.
Thanks,
Tom
If FSGSBASE reverted is disabled (as Tom did on the command-line), then
the RDPID path isn't hit.
Fun.
