From: Marc Zyngier <maz@kernel.org> To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Cc: kernel-team@android.com Subject: [PATCH] KVM: arm64: Don't access PMCR_EL0 when no PMU is available Date: Thu, 10 Dec 2020 08:30:59 +0000 [thread overview] Message-ID: <20201210083059.1277162-1-maz@kernel.org> (raw) We reset the guest's view of PMCR_EL0 unconditionally, based on the host's view of this register. It is however legal for an imnplementation not to provide any PMU, resulting in an UNDEF. The obvious fix is to skip the reset of this shadow register when no PMU is available, sidestepping the issue entirely. If no PMU is available, the guest is not able to request a virtual PMU anyway, so not doing nothing is the right thing to do! It is unlikely that this bug can hit any HW implementation though, as they all provide a PMU. It has been found using nested virt with the host KVM not implementing the PMU itself. Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register") Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/kvm/sys_regs.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index bc15246775d0..6c64d010102b 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -923,6 +923,10 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) { u64 pmcr, val; + /* No PMU available, PMCR_EL0 may UNDEF... */ + if (!kvm_arm_support_pmu_v3()) + return; + pmcr = read_sysreg(pmcr_el0); /* * Writable bits of PMCR_EL0 (ARMV8_PMU_PMCR_MASK) are reset to UNKNOWN -- 2.29.2 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org> To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Cc: James Morse <james.morse@arm.com>, Alexandru Elisei <alexandru.elisei@arm.com>, kernel-team@android.com, Julien Thierry <julien.thierry.kdev@gmail.com>, Suzuki K Poulose <suzuki.poulose@arm.com> Subject: [PATCH] KVM: arm64: Don't access PMCR_EL0 when no PMU is available Date: Thu, 10 Dec 2020 08:30:59 +0000 [thread overview] Message-ID: <20201210083059.1277162-1-maz@kernel.org> (raw) We reset the guest's view of PMCR_EL0 unconditionally, based on the host's view of this register. It is however legal for an imnplementation not to provide any PMU, resulting in an UNDEF. The obvious fix is to skip the reset of this shadow register when no PMU is available, sidestepping the issue entirely. If no PMU is available, the guest is not able to request a virtual PMU anyway, so not doing nothing is the right thing to do! It is unlikely that this bug can hit any HW implementation though, as they all provide a PMU. It has been found using nested virt with the host KVM not implementing the PMU itself. Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register") Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/kvm/sys_regs.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index bc15246775d0..6c64d010102b 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -923,6 +923,10 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) { u64 pmcr, val; + /* No PMU available, PMCR_EL0 may UNDEF... */ + if (!kvm_arm_support_pmu_v3()) + return; + pmcr = read_sysreg(pmcr_el0); /* * Writable bits of PMCR_EL0 (ARMV8_PMU_PMCR_MASK) are reset to UNKNOWN -- 2.29.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2020-12-10 8:31 UTC|newest] Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-10 8:30 Marc Zyngier [this message] 2020-12-10 8:30 ` [PATCH] KVM: arm64: Don't access PMCR_EL0 when no PMU is available Marc Zyngier 2020-12-10 10:12 ` Alexandru Elisei 2020-12-10 10:12 ` Alexandru Elisei 2020-12-10 11:16 ` Marc Zyngier 2020-12-10 11:16 ` Marc Zyngier 2020-12-10 12:22 ` Alexandru Elisei 2020-12-10 12:22 ` Alexandru Elisei 2021-01-04 15:47 ` Qian Cai 2021-01-04 15:47 ` Qian Cai 2021-01-04 15:47 ` Qian Cai 2021-01-04 16:08 ` Marc Zyngier 2021-01-04 16:08 ` Marc Zyngier 2021-01-04 16:08 ` Marc Zyngier 2021-01-04 16:22 ` Qian Cai 2021-01-04 16:22 ` Qian Cai 2021-01-04 16:22 ` Qian Cai 2021-01-04 16:27 ` Marc Zyngier 2021-01-04 16:27 ` Marc Zyngier 2021-01-04 16:27 ` Marc Zyngier 2021-01-04 18:20 ` Qian Cai 2021-01-04 18:20 ` Qian Cai 2021-01-04 18:20 ` Qian Cai 2021-01-04 18:26 ` Marc Zyngier 2021-01-04 18:26 ` Marc Zyngier 2021-01-04 18:26 ` Marc Zyngier 2021-01-04 18:42 ` Qian Cai 2021-01-04 18:42 ` Qian Cai 2021-01-04 18:42 ` Qian Cai 2021-01-04 19:32 ` Marc Zyngier 2021-01-04 19:32 ` Marc Zyngier 2021-01-04 19:32 ` Marc Zyngier
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