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Groups > linux.kernel > #1553488
| From | Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 4.8 53/96] arm64: KVM: pmu: Reset PMSELR_EL0.SEL to a sane value before entering the guest |
| Date | 2017-01-07 00:10 +0100 |
| Message-ID | <sWLO3-sV-67@gated-at.bofh.it> (permalink) |
| References | <sWKyC-7RC-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marc Zyngier <marc.zyngier@arm.com> 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> --- arch/arm64/kvm/hyp/switch.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/arch/arm64/kvm/hyp/switch.c +++ b/arch/arm64/kvm/hyp/switch.c @@ -82,7 +82,13 @@ static void __hyp_text __activate_traps( 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()();
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[PATCH 4.8 00/96] 4.8.17-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 17/96] hv: acquire vmbus_connection.channel_mutex in vmbus_free_channels() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 52/96] s390/kexec: use node 0 when re-adding crash kernel memory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 26/96] drm/nouveau/ltc: protect clearing of comptags with mutex Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 03/96] perf/x86: Fix exclusion of BTS and LBR for Goldmont Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 53/96] arm64: KVM: pmu: Reset PMSELR_EL0.SEL to a sane value before entering the guest Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 06/96] cfg80211/mac80211: fix BSS leaks when abandoning assoc attempts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 [PATCH 4.8 55/96] md/raid5: limit request size according to implementation limits Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-01-07 00:10 +0100 Re: [PATCH 4.8 00/96] 4.8.17-stable review Shuah Khan <shuah.kh@samsung.com> - 2017-01-07 03:10 +0100 Re: [PATCH 4.8 00/96] 4.8.17-stable review Guenter Roeck <linux@roeck-us.net> - 2017-01-07 17:00 +0100
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