On 2021/3/8 15:12, Dmitry Vyukov wrote:
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
Sorry, I couldn't reproduce any VMX abort with "-cpu max,-pmu".
Doe this patch fix this "unexpected kernel reboot" issue ?
If so, you may add "Tested-by" for more attention.
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();
/*
