4.9-stable review patch. If anyone has any objections, please let me know.
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From: Mark Rutland mark.rutland@arm.com
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
--- arch/arm/kvm/arm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -1092,8 +1092,6 @@ static void cpu_init_hyp_mode(void *dumm
__cpu_init_hyp_mode(pgd_ptr, hyp_stack_ptr, vector_ptr); __cpu_init_stage2(); - - 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) cpu_init_hyp_mode(NULL); } + + kvm_arm_init_debug(); }
static void cpu_hyp_reset(void)