diff options
| author | Marc Zyngier <marc.zyngier@arm.com> | 2016-12-06 14:34:22 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-09 08:32:22 +0100 |
| commit | 959e95305f1316475dbbfa5b366d82d5ac65562b (patch) | |
| tree | e87a4415ef01d81aad5c8adcf3a5867abd2874be /arch | |
| parent | 111e0ccaf979c688ca8b56e96561e7207e971b6a (diff) | |
arm64: KVM: pmu: Reset PMSELR_EL0.SEL to a sane value before entering the guest
commit 21cbe3cc8a48ff17059912e019fbde28ed54745a upstream.
The ARMv8 architecture allows the cycle counter to be configured
by setting PMSELR_EL0.SEL==0x1f and then accessing PMXEVTYPER_EL0,
hence accessing PMCCFILTR_EL0. But it disallows the use of
PMSELR_EL0.SEL==0x1f to access the cycle counter itself through
PMXEVCNTR_EL0.
Linux itself doesn't violate this rule, but we may end up with
PMSELR_EL0.SEL being set to 0x1f when we enter a guest. If that
guest accesses PMXEVCNTR_EL0, the access may UNDEF at EL1,
despite the guest not having done anything wrong.
In order to avoid this unfortunate course of events (haha!), let's
sanitize PMSELR_EL0 on guest entry. This ensures that the guest
won't explode unexpectedly.
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/kvm/hyp/switch.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c index 83037cd62d01..0c848c18ca44 100644 --- a/arch/arm64/kvm/hyp/switch.c +++ b/arch/arm64/kvm/hyp/switch.c @@ -85,7 +85,13 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu) write_sysreg(val, hcr_el2); /* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */ write_sysreg(1 << 15, hstr_el2); - /* Make sure we trap PMU access from EL0 to EL2 */ + /* + * Make sure we trap PMU access from EL0 to EL2. Also sanitize + * PMSELR_EL0 to make sure it never contains the cycle + * counter, which could make a PMXEVCNTR_EL0 access UNDEF at + * EL1 instead of being trapped to EL2. + */ + write_sysreg(0, pmselr_el0); write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0); write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); __activate_traps_arch()(); |