arm64: KVM: Hide PMU from guests when disabled

Since commit 93390c0a1b20 ("arm64: KVM: Hide unsupported AArch64 CPU
features from guests") we can hide cpu features from guests. Apply
this to a long standing issue where guests see a PMU available, but
it's not, because it was not enabled by KVM's userspace.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 1830ebc227d18d7c5ad06e8f1858bbe8f33fa53a..503144f13af02231c1be371e5f86fd3f6d5d55b8 100644 (file)
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -881,18 +881,25 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
 }
 
 /* Read a sanitised cpufeature ID register by sys_reg_desc */
-static u64 read_id_reg(struct sys_reg_desc const *r, bool raz)
+static u64 read_id_reg(struct kvm_vcpu *vcpu,
+                      struct sys_reg_desc const *r,
+                      bool raz)
 {
        u32 id = sys_reg((u32)r->Op0, (u32)r->Op1,
                         (u32)r->CRn, (u32)r->CRm, (u32)r->Op2);
        u64 val = raz ? 0 : read_sanitised_ftr_reg(id);
 
-       if (id == SYS_ID_AA64PFR0_EL1) {
+       switch (id) {
+       case SYS_ID_AA64DFR0_EL1:
+               if (!kvm_arm_pmu_v3_ready(vcpu))
+                       val &= ~(0xfUL << ID_AA64DFR0_PMUVER_SHIFT);
+               break;
+       case SYS_ID_AA64PFR0_EL1:
                if (val & (0xfUL << ID_AA64PFR0_SVE_SHIFT))
                        pr_err_once("kvm [%i]: SVE unsupported for guests, suppressing\n",
                                    task_pid_nr(current));
-
                val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
+               break;
        }
 
        return val;
@@ -908,7 +915,7 @@ static bool __access_id_reg(struct kvm_vcpu *vcpu,
        if (p->is_write)
                return write_to_read_only(vcpu, p, r);
 
-       p->regval = read_id_reg(r, raz);
+       p->regval = read_id_reg(vcpu, r, raz);
        return true;
 }
 
@@ -937,17 +944,17 @@ static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
  * are stored, and for set_id_reg() we don't allow the effective value
  * to be changed.
  */
-static int __get_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
-                       bool raz)
+static int __get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+                       void __user *uaddr, bool raz)
 {
        const u64 id = sys_reg_to_index(rd);
-       const u64 val = read_id_reg(rd, raz);
+       const u64 val = read_id_reg(vcpu, rd, raz);
 
        return reg_to_user(uaddr, &val, id);
 }
 
-static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
-                       bool raz)
+static int __set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+                       void __user *uaddr, bool raz)
 {
        const u64 id = sys_reg_to_index(rd);
        int err;
@@ -958,7 +965,7 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
                return err;
 
        /* This is what we mean by invariant: you can't change it. */
-       if (val != read_id_reg(rd, raz))
+       if (val != read_id_reg(vcpu, rd, raz))
                return -EINVAL;
 
        return 0;
@@ -967,25 +974,25 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
 static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
                      const struct kvm_one_reg *reg, void __user *uaddr)
 {
-       return __get_id_reg(rd, uaddr, false);
+       return __get_id_reg(vcpu, rd, uaddr, false);
 }
 
 static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
                      const struct kvm_one_reg *reg, void __user *uaddr)
 {
-       return __set_id_reg(rd, uaddr, false);
+       return __set_id_reg(vcpu, rd, uaddr, false);
 }
 
 static int get_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
                          const struct kvm_one_reg *reg, void __user *uaddr)
 {
-       return __get_id_reg(rd, uaddr, true);
+       return __get_id_reg(vcpu, rd, uaddr, true);
 }
 
 static int set_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
                          const struct kvm_one_reg *reg, void __user *uaddr)
 {
-       return __set_id_reg(rd, uaddr, true);
+       return __set_id_reg(vcpu, rd, uaddr, true);
 }
 
 /* sys_reg_desc initialiser for known cpufeature ID registers */