[PATCH] x86/kvm/pmu: Set AMD's virt PMU version to 1

Borislav Petkov
2019-05-08T17:03:03Z

From: Borislav Petkov <bp@suse.de>

After commit:

672ff6cff80c ("KVM: x86: Raise #GP when guest vCPU do not support PMU")

my AMD guests started #GPing like this:

general protection fault: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 4355 Comm: bash Not tainted 5.1.0-rc6+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:x86_perf_event_update+0x3b/0xa0

with Code: pointing to RDPMC. It is RDPMC because the guest has the
hardware watchdog CONFIG_HARDLOCKUP_DETECTOR_PERF enabled which uses
perf. Instrumenting kvm_pmu_rdpmc() some, showed that it fails due to:

if (!pmu->version)
return 1;

which the above commit added. Since AMD's PMU leaves the version at 0,
that causes the #GP injection into the guest.

Set pmu->version arbitrarily to 1 and move it above the non-applicable
struct kvm_pmu members.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Cc: kvm@vger.kernel.org
Cc: Liran Alon <liran.alon@oracle.com>
Cc: Mihai Carabas <mihai.carabas@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
---
arch/x86/kvm/pmu_amd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu_amd.c b/arch/x86/kvm/pmu_amd.c
index 1495a735b38e..50fa9450fcf1 100644
--- a/arch/x86/kvm/pmu_amd.c
+++ b/arch/x86/kvm/pmu_amd.c
@@ -269,10 +269,10 @@ static void amd_pmu_refresh(struct kvm_vcpu *vcpu)

pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << 48) - 1;
pmu->reserved_bits = 0xffffffff00200000ull;
+ pmu->version = 1;
/* not applicable to AMD; but clean them to prevent any fall out */
pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
pmu->nr_arch_fixed_counters = 0;
- pmu->version = 0;
pmu->global_status = 0;
}

--
2.21.0