On 6/12/2025 5:18 PM, Sean Christopherson wrote: >> Read the VMCS exit qualification unconditionally since almost all >> upcoming CPUs are expected to enable FRED and NMI-source together. In >> the rare case that NMI-source isn't enabled, the extra VMREAD would be >> harmless since the exit qualification is expected to be zero. > > Nit, instead of "is expected to be zero", something like this > > harmless since the exit qualification is architecturally guaranteed to be > zero on CPUs that don't support NMI-source reporting. Per the SDM's > "Exit qualification" subsection of "Basic VM-Exit Information": > > For all other VM exits, this field is cleared. > -- > Looks good. Clarifying it explicitly reduces ambiguity. If this patchset gets applied directly, I am hoping the clarification can be included while applying. If we end up doing another version, I'll add it to the log. > to make it very explicit that reading the exit qualification on older CPUs is 100% > safe, e.g. even on non-FRED CPUs (see https://lore.kernel.org/all/aBUiwLV4ZY2HdRbz@xxxxxxxxxx). > That's interesting. Thanks for the link. >> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> >> Originally-by: Zeng Guang <guang.zeng@xxxxxxxxx> >> Signed-off-by: Sohil Mehta <sohil.mehta@xxxxxxxxx> >> --- > > Acked-by: Sean Christopherson <seanjc@xxxxxxxxxx> Thank you!
