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authorMark Rutland <mark.rutland@arm.com>2018-10-17 17:42:10 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-11-21 09:26:04 +0100
commit7088c66504c236003cb2f138d9fec9f7c6076c40 (patch)
parentcc5bd86e271d97d8b29ba7524074600344a4505a (diff)
KVM: arm64: Fix caching of host MDCR_EL2 value
commit da5a3ce66b8bb51b0ea8a89f42aac153903f90fb upstream. 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. Cc: Christopher Dall <christoffer.dall@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: stable@vger.kernel.org Fixes: 1e947bad0b63b351 ("arm64: KVM: Skip HYP setup when already running in HYP") Tested-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 20436972537f..a670c70f4def 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -1092,8 +1092,6 @@ static void cpu_init_hyp_mode(void *dummy)
__cpu_init_hyp_mode(pgd_ptr, hyp_stack_ptr, vector_ptr);
- kvm_arm_init_debug();
static void cpu_hyp_reinit(void)
@@ -1108,6 +1106,8 @@ static void cpu_hyp_reinit(void)
if (__hyp_get_vectors() == hyp_default_vectors)
+ kvm_arm_init_debug();
static void cpu_hyp_reset(void)