x86/perf: Use RET0 as default for guest_get_msrs to handle "no PMU" case
Initialize x86_pmu.guest_get_msrs to return 0/NULL to handle the "nop" case. Patching in perf_guest_get_msrs_nop() during setup does not work if there is no PMU, as setup bails before updating the static calls, leaving x86_pmu.guest_get_msrs NULL and thus a complete nop. Ultimately, this causes VMX abort on VM-Exit due to KVM putting random garbage from the stack into the MSR load list. Add a comment in KVM to note that nr_msrs is valid if and only if the return value is non-NULL. Fixes: abd562df ("x86/perf: Use static_call for x86_pmu.guest_get_msrs") Reported-by:Dmitry Vyukov <dvyukov@google.com> Reported-by:
<syzbot+cce9ef2dd25246f815ee@syzkaller.appspotmail.com> Suggested-by:
Peter Zijlstra <peterz@infradead.org> Signed-off-by:
Sean Christopherson <seanjc@google.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210309171019.1125243-1-seanjc@google.com
parent
afbef301
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