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KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status

PATCH In review Raghavendra Rao Ananta 2 participants 2 messages Dec 16, 2024 – Dec 17, 2024 Stable branch

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Raghavendra Rao Ananta

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PATCH 1/1 KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status

commit 54bbee190d42166209185d89070c58a343bf514b upstream.

DDI0487K.a D13.3.1 describes the PMU overflow condition, which evaluates to true if any counter's global enable (PMCR_EL0.E), overflow flag (PMOVSSET_EL0[n]), and interrupt enable (PMINTENSET_EL1[n]) are all 1. Of note, this does not require a counter to be enabled
(i.e. PMCNTENSET_EL0[n] = 1) to generate an overflow.

Align kvm_pmu_overflow_status() with the reality of the architecture and stop using PMCNTENSET_EL0 as part of the overflow condition. The bug was discovered while running an SBSA PMU test [*], which only sets PMCR.E, PMOVSSET<0>, PMINTENSET<0>, and expects an overflow interrupt.

Cc [email protected]
Fixes 76d883c4e640 ("arm64: KVM: Add access handler for PMOVSSET and PMOVSCLR register")
Link https://github.com/ARM-software/sbsa-acs/blob/master/test_pool/pmu/operating_system/test_pmu001.c
Signed-off-by Raghavendra Rao Ananta <[email protected]>
[ oliver: massaged changelog ]
Reviewed-by Marc Zyngier <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Oliver Upton <[email protected]>
---
 virt/kvm/arm/pmu.c | 1 -
 1 file changed, 1 deletion(-)
virt/kvm/arm/pmu.c +0 -1
index 4c08fd009768..9732c5e0ed22 100644
@@ -357,7 +357,6 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
 
 	if ((__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E)) {
 		reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
-		reg &= __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
 		reg &= __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
 		reg &= kvm_pmu_valid_counter_mask(vcpu);
 	}

base-commit: 6708005a36cfdb32aa991ebd9ea172e1183231ef

Signature · 1 line
2.47.1.613.gc27f4b7a9f-goog
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#1 lore raw

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: 54bbee190d42166209185d89070c58a343bf514b

Status in newer kernel trees:
6.12.y | Present (different SHA1: 8b6916f4cf7d)

Note: The patch differs from the upstream commit:
---
Failed to apply patch cleanly, falling back to interdiff...

interdiff error output:
/home/sasha/stable/mailbot.sh: line 525: interdiff: command not found interdiff failed, falling back to standard diff...
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Failed     |  N/A       |
| stable/linux-6.6.y        |  Failed     |  N/A       |
| stable/linux-6.1.y        |  Failed     |  N/A       |
| stable/linux-5.15.y       |  Failed     |  N/A       |
| stable/linux-5.10.y       |  Failed     |  N/A       |
| stable/linux-5.4.y        |  Success    |  Success   |