linux-kernel - [PATCH 5.12 304/700] KVM: arm64: Dont zero the cycle count register when PMCR

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Message-Id: <20210712061008.740786960@linuxfoundation.org>
Date:   Mon, 12 Jul 2021 08:06:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexandru Elisei <alexandru.elisei@....com>,
        Marc Zyngier <maz@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 304/700] KVM: arm64: Dont zero the cycle count register when PMCR_EL0.P is set

From: Alexandru Elisei <alexandru.elisei@....com>

[ Upstream commit 2a71fabf6a1bc9162a84e18d6ab991230ca4d588 ]

According to ARM DDI 0487G.a, page D13-3895, setting the PMCR_EL0.P bit to
1 has the following effect:

"Reset all event counters accessible in the current Exception level, not
including PMCCNTR_EL0, to zero."

Similar behaviour is described for AArch32 on page G8-7022. Make it so.

Fixes: c01d6a18023b ("KVM: arm64: pmu: Only handle supported event counters")
Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20210618105139.83795-1-alexandru.elisei@arm.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kvm/pmu-emul.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index e9699d10d2bd..14957f7c7303 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -578,6 +578,7 @@ void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val)
 		kvm_pmu_set_counter_value(vcpu, ARMV8_PMU_CYCLE_IDX, 0);
 
 	if (val & ARMV8_PMU_PMCR_P) {
+		mask &= ~BIT(ARMV8_PMU_CYCLE_IDX);
 		for_each_set_bit(i, &mask, 32)
 			kvm_pmu_set_counter_value(vcpu, i, 0);
 	}
-- 
2.30.2