linux-kernel - [PATCH stable] KVM: x86: remove PMU FIXED_CTR3 from msrs_to_save

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Message-Id: <20220118091107.1007603-1-pbonzini@redhat.com>
Date:   Tue, 18 Jan 2022 04:11:07 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Jim Mattson <jmattson@...gle.com>, Wei Wang <wei.w.wang@...el.com>,
        stable@...r.kernel.org
Subject: [PATCH stable] KVM: x86: remove PMU FIXED_CTR3 from msrs_to_save_all

From: Wei Wang <wei.w.wang@...el.com>

[ upstream commit 9fb12fe5b93b94b9e607509ba461e17f4cc6a264 ]

The fixed counter 3 is used for the Topdown metrics, which hasn't been
enabled for KVM guests. Userspace accessing to it will fail as it's not
included in get_fixed_pmc(). This breaks KVM selftests on ICX+ machines,
which have this counter.

To reproduce it on ICX+ machines, ./state_test reports:
==== Test Assertion Failure ====
lib/x86_64/processor.c:1078: r == nmsrs
pid=4564 tid=4564 - Argument list too long
1  0x000000000040b1b9: vcpu_save_state at processor.c:1077
2  0x0000000000402478: main at state_test.c:209 (discriminator 6)
3  0x00007fbe21ed5f92: ?? ??:0
4  0x000000000040264d: _start at ??:?
 Unexpected result from KVM_GET_MSRS, r: 17 (failed MSR was 0x30c)

With this patch, it works well.

Signed-off-by: Wei Wang <wei.w.wang@...el.com>
Message-Id: <20211217124934.32893-1-wei.w.wang@...el.com>
Fixes: e2ada66ec418 ("kvm: x86: Add Intel PMU MSRs to msrs_to_save[]")
Cc: stable@...r.kernel.org # 5.4.x
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a2972fdae82..d490b83d640c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1331,7 +1331,7 @@ static const u32 msrs_to_save_all[] = {
 	MSR_IA32_UMWAIT_CONTROL,
 
 	MSR_ARCH_PERFMON_FIXED_CTR0, MSR_ARCH_PERFMON_FIXED_CTR1,
-	MSR_ARCH_PERFMON_FIXED_CTR0 + 2, MSR_ARCH_PERFMON_FIXED_CTR0 + 3,
+	MSR_ARCH_PERFMON_FIXED_CTR0 + 2,
 	MSR_CORE_PERF_FIXED_CTR_CTRL, MSR_CORE_PERF_GLOBAL_STATUS,
 	MSR_CORE_PERF_GLOBAL_CTRL, MSR_CORE_PERF_GLOBAL_OVF_CTRL,
 	MSR_ARCH_PERFMON_PERFCTR0, MSR_ARCH_PERFMON_PERFCTR1,
-- 
2.31.1