On Mon, Mar 8, 2021 at 3:26 AM Xu, Like <like.xu@xxxxxxxxx> wrote: > > On 2021/3/6 6:33, Sean Christopherson wrote: > > Handle a NULL x86_pmu.guest_get_msrs at invocation instead of patching > > in perf_guest_get_msrs_nop() during setup. If there is no PMU, setup > > "If there is no PMU" ... > > How to set up this kind of environment, > and what changes are needed in .config or boot parameters ? Hi Xu, This can be reproduced in qemu with "-cpu max,-pmu" flag using this reproducer: https://groups.google.com/g/syzkaller-bugs/c/D8eHw3LIOd0/m/L2G0lVkVBAAJ > > 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. > > > > Fixes: abd562df94d1 ("x86/perf: Use static_call for x86_pmu.guest_get_msrs") > > Cc: Like Xu <like.xu@xxxxxxxxxxxxxxx> > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > Cc: Jim Mattson <jmattson@xxxxxxxxxx> > > Cc: kvm@xxxxxxxxxxxxxxx > > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > --- > > arch/x86/events/core.c | 16 +++++----------- > > 1 file changed, 5 insertions(+), 11 deletions(-) > > > > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c > > index 6ddeed3cd2ac..ff874461f14c 100644 > > --- a/arch/x86/events/core.c > > +++ b/arch/x86/events/core.c > > @@ -671,7 +671,11 @@ void x86_pmu_disable_all(void) > > > > struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr) > > { > > - return static_call(x86_pmu_guest_get_msrs)(nr); > > + if (x86_pmu.guest_get_msrs) > > + return static_call(x86_pmu_guest_get_msrs)(nr); > > How about using "static_call_cond" per commit "452cddbff7" ? > > > + > > + *nr = 0; > > + return NULL; > > } > > EXPORT_SYMBOL_GPL(perf_guest_get_msrs); > > > > @@ -1944,13 +1948,6 @@ static void _x86_pmu_read(struct perf_event *event) > > x86_perf_event_update(event); > > } > > > > -static inline struct perf_guest_switch_msr * > > -perf_guest_get_msrs_nop(int *nr) > > -{ > > - *nr = 0; > > - return NULL; > > -} > > - > > static int __init init_hw_perf_events(void) > > { > > struct x86_pmu_quirk *quirk; > > @@ -2024,9 +2021,6 @@ static int __init init_hw_perf_events(void) > > if (!x86_pmu.read) > > x86_pmu.read = _x86_pmu_read; > > > > - if (!x86_pmu.guest_get_msrs) > > - x86_pmu.guest_get_msrs = perf_guest_get_msrs_nop; > > - > > x86_pmu_static_call_update(); > > > > /* >
