From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Wed, 17 Oct 2018 17:42:10 +0100 Subject: [PATCH] kvm: arm64: fix caching of host MDCR_EL2 value Message-ID: <20181017164210.16094-1-mark.rutland@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org At boot time, KVM stashes the host MDCR_EL2 value, but only does this when the kernel is not running in hyp mode (i.e. is non-VHE). In these cases, the stashed value of MDCR_EL2.HPMN happens to be zero, which can lead to CONSTRAINED UNPREDICTABLE behaviour. Since we use this value to derive the MDCR_EL2 value when switching to/from a guest, after a guest have been run, the performance counters do not behave as expected. This has been observed to result in accesses via PMXEVTYPER_EL0 and PMXEVCNTR_EL0 not affecting the relevant counters, resulting in events not being counted. In these cases, only the fixed-purpose cycle counter appears to work as expected. Fix this by always stashing the host MDCR_EL2 value, regardless of VHE. Fixes: 1e947bad0b63b351 ("arm64: KVM: Skip HYP setup when already running in HYP") Signed-off-by: Mark Rutland Cc: Christopher Dall Cc: James Morse Cc: Marc Zyngier Cc: Robin Murphy Cc: Will Deacon Cc: kvmarm at lists.cs.columbia.edu --- virt/kvm/arm/arm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index c92053bc3f96..8fb31a7cc22c 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -1295,8 +1295,6 @@ static void cpu_init_hyp_mode(void *dummy) __cpu_init_hyp_mode(pgd_ptr, hyp_stack_ptr, vector_ptr); __cpu_init_stage2(); - - kvm_arm_init_debug(); } static void cpu_hyp_reset(void) @@ -1320,6 +1318,8 @@ static void cpu_hyp_reinit(void) cpu_init_hyp_mode(NULL); } + kvm_arm_init_debug(); + if (vgic_present) kvm_vgic_init_cpu_hardware(); } -- 2.11.0