[PATCH v1] KVM: arm64: Use the host kvm_host_data for nr_event_counters

[Vincent Donnefort]

nr_event_counters is only used by the host to populate mdcr_el2.
However, host_data_ptr() for pKVM switches between the hypervisor copy
of kvm_host_data before it is deprivileged to the host copy after.

So kvm_init_host_debug_data() initialises nr_event_counters in the
hypervisor's kvm_host_data, while kvm_arm_setup_mdcr_el2() reads the
host copy which is 0. With a HPMN of 0, this stops programmable event
counters from counting a non-protected guest.

Always use the host copy for nr_event_counters.

Fixes: 2417218f2f23 ("KVM: arm64: Get rid of __kvm_get_mdcr_el2() and related warts")
Signed-off-by: Vincent Donnefort <vdonnefort at google.com>
---
 arch/arm64/kvm/debug.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index f4d7b12045e8..a00771339c62 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -44,7 +44,7 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
 	 * to disable guest access to the profiling and trace buffers
 	 */
 	vcpu->arch.mdcr_el2 = FIELD_PREP(MDCR_EL2_HPMN,
-					 *host_data_ptr(nr_event_counters));
+					 __this_cpu_read(kvm_host_data.nr_event_counters));
 	vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
 				MDCR_EL2_TPMS |
 				MDCR_EL2_TTRF |
@@ -80,8 +80,8 @@ void kvm_init_host_debug_data(void)
 								   ID_AA64DFR0_EL1_PMUVer_SHIFT);
 
 	if (pmuv3_implemented(pmuver))
-		*host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N,
-							      read_sysreg(pmcr_el0));
+		__this_cpu_write(kvm_host_data.nr_event_counters,
+				 FIELD_GET(ARMV8_PMU_PMCR_N, read_sysreg(pmcr_el0)));
 
 	*host_data_ptr(debug_brps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0);
 	*host_data_ptr(debug_wrps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0);

base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
-- 
2.56.0.257.gf7497c7d27-goog