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From: James Clark <james.clark@arm.com>
To: kvmarm@lists.linux.dev
Cc: James Clark <james.clark@arm.com>, Marc Zyngier <maz@kernel.org>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Oliver Upton <oliver.upton@linux.dev>,
Catalin Marinas <catalin.marinas@arm.com>,
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linux-kernel@vger.kernel.org
Subject: [PATCH 1/1] KVM: arm64: PMU: Fix PMCR_EL0 reset value
Date: Fri, 9 Dec 2022 16:44:46 +0000
Message-Id: <20221209164446.1972014-2-james.clark@arm.com>
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KVM: arm64: PMU: Fix PMCR_EL0 reset value
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Commit Message
James Clark
Dec. 9, 2022, 4:44 p.m. UTC
ARMV8_PMU_PMCR_N_MASK is an unshifted value which results in the wrong
reset value for PMCR_EL0, so shift it to fix it.
This fixes the following error when running qemu:
$ qemu-system-aarch64 -cpu host -machine type=virt,accel=kvm -kernel ...
target/arm/helper.c:1813: pmevcntr_rawwrite: Assertion `counter < pmu_num_counters(env)' failed.
Fixes: 292e8f149476 ("KVM: arm64: PMU: Simplify PMCR_EL0 reset handling")
Signed-off-by: James Clark <james.clark@arm.com>
---
arch/arm64/kvm/sys_regs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Comments
On Fri, Dec 09, 2022 at 04:44:46PM +0000, James Clark wrote: > ARMV8_PMU_PMCR_N_MASK is an unshifted value which results in the wrong > reset value for PMCR_EL0, so shift it to fix it. That's just mean. *_MASK tends to be a shifted mask, although it would appear that asm/perf_event.h does not follow this convention. Fixing that would be nice (as I'm sure somebody else will get burned by this), but for the sake of an immediate fix: > This fixes the following error when running qemu: > > $ qemu-system-aarch64 -cpu host -machine type=virt,accel=kvm -kernel ... > > target/arm/helper.c:1813: pmevcntr_rawwrite: Assertion `counter < pmu_num_counters(env)' failed. > > Fixes: 292e8f149476 ("KVM: arm64: PMU: Simplify PMCR_EL0 reset handling") > Signed-off-by: James Clark <james.clark@arm.com> Reviewed-by: Oliver Upton <oliver.upton@linux.dev> -- Thanks, Oliver > --- > arch/arm64/kvm/sys_regs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index d5ee52d6bf73..c6cbfe6b854b 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -646,7 +646,7 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) > return; > > /* Only preserve PMCR_EL0.N, and reset the rest to 0 */ > - pmcr = read_sysreg(pmcr_el0) & ARMV8_PMU_PMCR_N_MASK; > + pmcr = read_sysreg(pmcr_el0) & (ARMV8_PMU_PMCR_N_MASK << ARMV8_PMU_PMCR_N_SHIFT); > if (!kvm_supports_32bit_el0()) > pmcr |= ARMV8_PMU_PMCR_LC; > > -- > 2.25.1 >
On Fri, 09 Dec 2022 17:58:31 +0000, Oliver Upton <oliver.upton@linux.dev> wrote: > > On Fri, Dec 09, 2022 at 04:44:46PM +0000, James Clark wrote: > > ARMV8_PMU_PMCR_N_MASK is an unshifted value which results in the wrong > > reset value for PMCR_EL0, so shift it to fix it. > > That's just mean. *_MASK tends to be a shifted mask, although it would > appear that asm/perf_event.h does not follow this convention. Fixing > that would be nice (as I'm sure somebody else will get burned by this), > but for the sake of an immediate fix: Well, that'll teach me the usual lesson: last minute changes without full non-regression testing are bound to end in disaster. > > > This fixes the following error when running qemu: > > > > $ qemu-system-aarch64 -cpu host -machine type=virt,accel=kvm -kernel ... > > > > target/arm/helper.c:1813: pmevcntr_rawwrite: Assertion `counter < pmu_num_counters(env)' failed. > > > > Fixes: 292e8f149476 ("KVM: arm64: PMU: Simplify PMCR_EL0 reset handling") > > Signed-off-by: James Clark <james.clark@arm.com> > > Reviewed-by: Oliver Upton <oliver.upton@linux.dev> Thanks both. I'll queue that ASAP as a fix. M.
On 12/9/22 23:28, Oliver Upton wrote: > On Fri, Dec 09, 2022 at 04:44:46PM +0000, James Clark wrote: >> ARMV8_PMU_PMCR_N_MASK is an unshifted value which results in the wrong >> reset value for PMCR_EL0, so shift it to fix it. > > That's just mean. *_MASK tends to be a shifted mask, although it would > appear that asm/perf_event.h does not follow this convention. Fixing > that would be nice (as I'm sure somebody else will get burned by this), > but for the sake of an immediate fix: New arch/arm64/tools/sysreg generates shifted i.e in place masks for register fields. Once all these PMU registers move into arch/arm64/tools/sysreg, this problem will be solved. > >> This fixes the following error when running qemu: >> >> $ qemu-system-aarch64 -cpu host -machine type=virt,accel=kvm -kernel ... >> >> target/arm/helper.c:1813: pmevcntr_rawwrite: Assertion `counter < pmu_num_counters(env)' failed. >> >> Fixes: 292e8f149476 ("KVM: arm64: PMU: Simplify PMCR_EL0 reset handling") >> Signed-off-by: James Clark <james.clark@arm.com> > > Reviewed-by: Oliver Upton <oliver.upton@linux.dev> > > -- > Thanks, > Oliver > >> --- >> arch/arm64/kvm/sys_regs.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c >> index d5ee52d6bf73..c6cbfe6b854b 100644 >> --- a/arch/arm64/kvm/sys_regs.c >> +++ b/arch/arm64/kvm/sys_regs.c >> @@ -646,7 +646,7 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) >> return; >> >> /* Only preserve PMCR_EL0.N, and reset the rest to 0 */ >> - pmcr = read_sysreg(pmcr_el0) & ARMV8_PMU_PMCR_N_MASK; >> + pmcr = read_sysreg(pmcr_el0) & (ARMV8_PMU_PMCR_N_MASK << ARMV8_PMU_PMCR_N_SHIFT); >> if (!kvm_supports_32bit_el0()) >> pmcr |= ARMV8_PMU_PMCR_LC; >> >> -- >> 2.25.1 >> > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Fri, Dec 09, 2022 at 05:58:31PM +0000, Oliver Upton wrote: > On Fri, Dec 09, 2022 at 04:44:46PM +0000, James Clark wrote: > > ARMV8_PMU_PMCR_N_MASK is an unshifted value which results in the wrong > > reset value for PMCR_EL0, so shift it to fix it. > > That's just mean. *_MASK tends to be a shifted mask, although it would > appear that asm/perf_event.h does not follow this convention. Fixing > that would be nice (as I'm sure somebody else will get burned by this), > but for the sake of an immediate fix: > Even kvm-unit-tests does this: arm/pmu.c: #define PMU_PMCR_N_SHIFT 11 #define PMU_PMCR_N_MASK 0x1f > > This fixes the following error when running qemu: > > > > $ qemu-system-aarch64 -cpu host -machine type=virt,accel=kvm -kernel ... > > > > target/arm/helper.c:1813: pmevcntr_rawwrite: Assertion `counter < pmu_num_counters(env)' failed. > > > > Fixes: 292e8f149476 ("KVM: arm64: PMU: Simplify PMCR_EL0 reset handling") > > Signed-off-by: James Clark <james.clark@arm.com> > > Reviewed-by: Oliver Upton <oliver.upton@linux.dev> > > -- > Thanks, > Oliver > > > --- > > arch/arm64/kvm/sys_regs.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > > index d5ee52d6bf73..c6cbfe6b854b 100644 > > --- a/arch/arm64/kvm/sys_regs.c > > +++ b/arch/arm64/kvm/sys_regs.c > > @@ -646,7 +646,7 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) > > return; > > > > /* Only preserve PMCR_EL0.N, and reset the rest to 0 */ > > - pmcr = read_sysreg(pmcr_el0) & ARMV8_PMU_PMCR_N_MASK; > > + pmcr = read_sysreg(pmcr_el0) & (ARMV8_PMU_PMCR_N_MASK << ARMV8_PMU_PMCR_N_SHIFT); > > if (!kvm_supports_32bit_el0()) > > pmcr |= ARMV8_PMU_PMCR_LC; > > > > -- > > 2.25.1 > > > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index d5ee52d6bf73..c6cbfe6b854b 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -646,7 +646,7 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) return; /* Only preserve PMCR_EL0.N, and reset the rest to 0 */ - pmcr = read_sysreg(pmcr_el0) & ARMV8_PMU_PMCR_N_MASK; + pmcr = read_sysreg(pmcr_el0) & (ARMV8_PMU_PMCR_N_MASK << ARMV8_PMU_PMCR_N_SHIFT); if (!kvm_supports_32bit_el0()) pmcr |= ARMV8_PMU_PMCR_LC;