[PATCH] KVM: arm64: Read PMUVer as unsigned

From: James Clark

Date: Thu Mar 05 2026 - 06:56:13 EST


ID_AA64DFR0_EL1.PMUVer is an unsigned field, so this skips
initialization of host_data_ptr(nr_event_counters) for PMUv3 for Armv8.8
onwards as they appear as negative values.

Fix it by reading it as unsigned.

Fixes: 2417218f2f23 ("KVM: arm64: Get rid of __kvm_get_mdcr_el2() and related warts")
Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
---
arch/arm64/kvm/debug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 3ad6b7c6e4ba..b8632edba9a3 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -76,7 +76,7 @@ void kvm_init_host_debug_data(void)
{
u64 dfr0 = read_sysreg(id_aa64dfr0_el1);

- if (cpuid_feature_extract_signed_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0)
+ if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0)
*host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N,
read_sysreg(pmcr_el0));


---
base-commit: c107785c7e8dbabd1c18301a1c362544b5786282
change-id: 20260305-james-kvm-pmuver-sign-fe830bdead2d

Best regards,
--
James Clark <james.clark@xxxxxxxxxx>