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I see that INVLPGB and TLBYSNC >> behavior in a VM is spec'ed in the AMD Programmer's Manual, but >> I wonder about their impact in a multi-tenant host like in a public >> cloud environment. And given what this patch set does in assigning >> global ASIDs, should X86_FEATURE_INVLPGB be disabled if >> running in a VM where the hypervisor for whatever reason has >> enabled INVLPGB/TLBSYNC in its VMs? >> > This patch series enables bare metal INVLPGB functionality. > > Virtual machines should probably not expose the INVPLGB > CPUID feature bit to guests, since virtual machine > invalidation seems to work differently than bare metal > invalidation. > > For one, the ASID seems to actually mean something in > SVM context, while trying to use the ASID in bare metal > blows up :) Note that global ASIDs (relative to VMs) are different from the broadcast ASIDs being used here. IIUC, the broadcast ASIDs here get translated to a PCID value (kern_pcid(asid) or user_pcid(asid) in patch #9). Thanks, Tom > >