Allow userspace to write ID_AA64DFR0_EL1, on the condition that only
the PMUver field can be altered and be at most the one that was
initially computed for the guest.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
arch/arm64/kvm/sys_regs.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 7a4cd644b9c0..4fa14b4ae2a6 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1247,6 +1247,40 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
return 0;
}
+static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
+ const struct sys_reg_desc *rd,
+ u64 val)
+{
+ u8 pmuver, host_pmuver;
+
+ host_pmuver = kvm_arm_pmu_get_pmuver_limit();
+
+ /*
+ * Allow AA64DFR0_EL1.PMUver to be set from userspace as long
+ * as it doesn't promise more than what the HW gives us. We
+ * allow an IMPDEF PMU though, only if no PMU is supported
+ * (KVM backward compatibility handling).
+ */
+ pmuver = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), val);
+ if (pmuver != ID_AA64DFR0_EL1_PMUVer_IMP_DEF && pmuver > host_pmuver)
+ return -EINVAL;
+
+ /* We already have a PMU, don't try to disable it... */
+ if (kvm_vcpu_has_pmu(vcpu) &&
+ (pmuver == 0 || pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF))
+ return -EINVAL;
+
+ /* We can only differ with PMUver, and anything else is an error */
+ val ^= read_id_reg(vcpu, rd);
+ val &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer);
+ if (val)
+ return -EINVAL;
+
+ vcpu->kvm->arch.dfr0_pmuver = pmuver;
+
+ return 0;
+}
+
/*
* cpufeature ID register user accessors
*
@@ -1508,7 +1542,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
ID_UNALLOCATED(4,7),
/* CRm=5 */
- ID_SANITISED(ID_AA64DFR0_EL1),
+ { SYS_DESC(SYS_ID_AA64DFR0_EL1), .access = access_id_reg,
+ .get_user = get_id_reg, .set_user = set_id_aa64dfr0_el1, },
ID_SANITISED(ID_AA64DFR1_EL1),
ID_UNALLOCATED(5,2),
ID_UNALLOCATED(5,3),
--
2.34.1
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