Re: [PATCH v3 4/6] KVM: arm64: Use per guest ID register for ID_AA64DFR0_EL1.PMUVer

With per guest ID registers, PMUver settings from userspace
can be stored in its corresponding ID register.

No functional change intended.

Signed-off-by: Jing Zhang <redacted>
---
 arch/arm64/include/asm/kvm_host.h | 11 ++++---
 arch/arm64/kvm/arm.c              |  6 ----
 arch/arm64/kvm/id_regs.c          | 52 ++++++++++++++++++++++++-------
 include/kvm/arm_pmu.h             |  6 ++--
 4 files changed, 51 insertions(+), 24 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f64347eb77c2..effb61a9a855 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h

@@ -218,6 +218,12 @@ struct kvm_arch {
 #define KVM_ARCH_FLAG_EL1_32BIT                                4
        /* PSCI SYSTEM_SUSPEND enabled for the guest */
 #define KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED           5
+       /*
+        * AA64DFR0_EL1.PMUver was set as ID_AA64DFR0_EL1_PMUVer_IMP_DEF
+        * or DFR0_EL1.PerfMon was set as ID_DFR0_EL1_PerfMon_IMPDEF from
+        * userspace for VCPUs without PMU.
+        */
+#define KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU             6

        unsigned long flags;

@@ -230,11 +236,6 @@ struct kvm_arch {

        cpumask_var_t supported_cpus;

-       struct {
-               u8 imp:4;
-               u8 unimp:4;
-       } dfr0_pmuver;
-
        /* Hypercall features firmware registers' descriptor */
        struct kvm_smccc_features smccc_feat;

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index c78d68d011cb..fb2de2cb98cb 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c

@@ -138,12 +138,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
        kvm_arm_set_default_id_regs(kvm);
        kvm_arm_init_hypercalls(kvm);

-       /*
-        * Initialise the default PMUver before there is a chance to
-        * create an actual PMU.
-        */
-       kvm->arch.dfr0_pmuver.imp = kvm_arm_pmu_get_pmuver_limit();
-
        return 0;

 err_free_cpumask:

diff --git a/arch/arm64/kvm/id_regs.c b/arch/arm64/kvm/id_regs.c
index 36859e4caf02..21ec8fc10d79 100644
--- a/arch/arm64/kvm/id_regs.c
+++ b/arch/arm64/kvm/id_regs.c

@@ -21,9 +21,12 @@
 static u8 vcpu_pmuver(const struct kvm_vcpu *vcpu)
 {
        if (kvm_vcpu_has_pmu(vcpu))
-               return vcpu->kvm->arch.dfr0_pmuver.imp;
-
-       return vcpu->kvm->arch.dfr0_pmuver.unimp;
+               return FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer),
+                               IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1));
+       else if (test_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags))
+               return ID_AA64DFR0_EL1_PMUVer_IMP_DEF;
+       else
+               return 0;
 }

 static u8 perfmon_to_pmuver(u8 perfmon)

@@ -256,10 +259,19 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
        if (val)
                return -EINVAL;

-       if (valid_pmu)
-               vcpu->kvm->arch.dfr0_pmuver.imp = pmuver;
-       else
-               vcpu->kvm->arch.dfr0_pmuver.unimp = pmuver;
+       if (valid_pmu) {
+               IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer);
+               IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1) |=
+                       FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), pmuver);
+
+               IDREG(vcpu->kvm, SYS_ID_DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_DFR0_EL1_PerfMon);
+               IDREG(vcpu->kvm, SYS_ID_DFR0_EL1) |=
+                       FIELD_PREP(ARM64_FEATURE_MASK(ID_DFR0_EL1_PerfMon), pmuver);

+       } else if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF) {
+               set_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
+       } else {
+               clear_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
+       }

        return 0;
 }

@@ -296,10 +308,19 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
        if (val)
                return -EINVAL;

-       if (valid_pmu)
-               vcpu->kvm->arch.dfr0_pmuver.imp = perfmon_to_pmuver(perfmon);
-       else
-               vcpu->kvm->arch.dfr0_pmuver.unimp = perfmon_to_pmuver(perfmon);
+       if (valid_pmu) {
+               IDREG(vcpu->kvm, SYS_ID_DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_DFR0_EL1_PerfMon);
+               IDREG(vcpu->kvm, SYS_ID_DFR0_EL1) |= FIELD_PREP(
+                       ARM64_FEATURE_MASK(ID_DFR0_EL1_PerfMon), perfmon_to_pmuver(perfmon));

+
+               IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer);
+               IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1) |= FIELD_PREP(
+                       ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), perfmon_to_pmuver(perfmon));
+       } else if (perfmon == ID_DFR0_EL1_PerfMon_IMPDEF) {
+               set_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
+       } else {
+               clear_bit(KVM_ARCH_FLAG_VCPU_HAS_IMP_DEF_PMU, &vcpu->kvm->arch.flags);
+       }

        return 0;
 }

@@ -543,4 +564,13 @@ void kvm_arm_set_default_id_regs(struct kvm *kvm)
        }

        IDREG(kvm, SYS_ID_AA64PFR0_EL1) = val;
+
+       /*
+        * Initialise the default PMUver before there is a chance to
+        * create an actual PMU.
+        */
+       IDREG(kvm, SYS_ID_AA64DFR0_EL1) &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer);
+       IDREG(kvm, SYS_ID_AA64DFR0_EL1) |=
+               FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer),
+                          kvm_arm_pmu_get_pmuver_limit());
 }

diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 628775334d5e..eef67b7d9751 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h

@@ -92,8 +92,10 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
 /*
  * Evaluates as true when emulating PMUv3p5, and false otherwise.
  */
-#define kvm_pmu_is_3p5(vcpu)                                           \
-       (vcpu->kvm->arch.dfr0_pmuver.imp >= ID_AA64DFR0_EL1_PMUVer_V3P5)
+#define kvm_pmu_is_3p5(vcpu)                                                                   \
+       (kvm_vcpu_has_pmu(vcpu) &&                                                              \