On Mon, Jun 03, 2024 at 05:02:22PM -0700, Zide Chen wrote: > Date: Mon, 3 Jun 2024 17:02:22 -0700 > From: Zide Chen <zide.c...@intel.com> > Subject: [PATCH V3 2/2] target/i386: Advertise MWAIT iff host supports > X-Mailer: git-send-email 2.34.1 > > host_cpu_realizefn() sets CPUID_EXT_MONITOR without consulting host/KVM > capabilities. This may cause problems: > > - If MWAIT/MONITOR is not available on the host, advertising this > feature to the guest and executing MWAIT/MONITOR from the guest > triggers #UD and the guest doesn't boot. This is because typically > #UD takes priority over VM-Exit interception checks and KVM doesn't > emulate MONITOR/MWAIT on #UD. > > - If KVM doesn't support KVM_X86_DISABLE_EXITS_MWAIT, MWAIT/MONITOR > from the guest are intercepted by KVM, which is not what cpu-pm=on > intends to do. > > In these cases, MWAIT/MONITOR should not be exposed to the guest. > > The logic in kvm_arch_get_supported_cpuid() to handle CPUID_EXT_MONITOR > is correct and sufficient, and we can't set CPUID_EXT_MONITOR after > x86_cpu_filter_features(). > > This was not an issue before commit 662175b91ff ("i386: reorder call to > cpu_exec_realizefn") because the feature added in the accel-specific > realizefn could be checked against host availability and filtered out. > > Additionally, it seems not a good idea to handle guest CPUID leaves in > host_cpu_realizefn(), and this patch merges host_cpu_enable_cpu_pm() > into kvm_cpu_realizefn(). > > Fixes: f5cc5a5c1686 ("i386: split cpu accelerators from cpu.c, using > AccelCPUClass") > Fixes: 662175b91ff2 ("i386: reorder call to cpu_exec_realizefn") > Signed-off-by: Zide Chen <zide.c...@intel.com> > ---
LGTM, Reviewed-by: Zhao Liu <zhao1....@intel.com>