KVM: arm64: Hide PMU registers from userspace when not available

It appears that while we are now able to properly hide PMU
registers from the guest when a PMU isn't available (either
because none has been configured, the host doesn't have
the PMU support compiled in, or that the HW doesn't have
one at all), we are still exposing more than we should to
userspace.

Introduce a visibility callback gating all the PMU registers,
which covers both usrespace and guest.
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/sys_regs.c

@@ -590,6 +590,15 @@ static void reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 	vcpu_write_sys_reg(vcpu, (1ULL << 31) | mpidr, MPIDR_EL1);
 }
 
+static unsigned int pmu_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *r)
+{
+	if (kvm_vcpu_has_pmu(vcpu))
+		return 0;
+
+	return REG_HIDDEN;
+}
+
 static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 {
 	u64 pmcr, val;
@@ -936,15 +945,18 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	{ SYS_DESC(SYS_DBGWCRn_EL1(n)),					\
 	  trap_wcr, reset_wcr, 0, 0,  get_wcr, set_wcr }
 
+#define PMU_SYS_REG(r)						\
+	SYS_DESC(r), .reset = reset_unknown, .visibility = pmu_visibility
+
 /* Macro to expand the PMEVCNTRn_EL0 register */
 #define PMU_PMEVCNTR_EL0(n)						\
-	{ SYS_DESC(SYS_PMEVCNTRn_EL0(n)),					\
-	  access_pmu_evcntr, reset_unknown, (PMEVCNTR0_EL0 + n), }
+	{ PMU_SYS_REG(SYS_PMEVCNTRn_EL0(n)),				\
+	  .access = access_pmu_evcntr, .reg = (PMEVCNTR0_EL0 + n), }
 
 /* Macro to expand the PMEVTYPERn_EL0 register */
 #define PMU_PMEVTYPER_EL0(n)						\
-	{ SYS_DESC(SYS_PMEVTYPERn_EL0(n)),					\
-	  access_pmu_evtyper, reset_unknown, (PMEVTYPER0_EL0 + n), }
+	{ PMU_SYS_REG(SYS_PMEVTYPERn_EL0(n)),				\
+	  .access = access_pmu_evtyper, .reg = (PMEVTYPER0_EL0 + n), }
 
 static bool undef_access(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 			 const struct sys_reg_desc *r)
@@ -1486,8 +1498,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
 
-	{ SYS_DESC(SYS_PMINTENSET_EL1), access_pminten, reset_unknown, PMINTENSET_EL1 },
-	{ SYS_DESC(SYS_PMINTENCLR_EL1), access_pminten, reset_unknown, PMINTENSET_EL1 },
+	{ PMU_SYS_REG(SYS_PMINTENSET_EL1),
+	  .access = access_pminten, .reg = PMINTENSET_EL1 },
+	{ PMU_SYS_REG(SYS_PMINTENCLR_EL1),
+	  .access = access_pminten, .reg = PMINTENSET_EL1 },
 
 	{ SYS_DESC(SYS_MAIR_EL1), access_vm_reg, reset_unknown, MAIR_EL1 },
 	{ SYS_DESC(SYS_AMAIR_EL1), access_vm_reg, reset_amair_el1, AMAIR_EL1 },
@@ -1526,23 +1540,36 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
 	{ SYS_DESC(SYS_CTR_EL0), access_ctr },
 
-	{ SYS_DESC(SYS_PMCR_EL0), access_pmcr, reset_pmcr, PMCR_EL0 },
-	{ SYS_DESC(SYS_PMCNTENSET_EL0), access_pmcnten, reset_unknown, PMCNTENSET_EL0 },
-	{ SYS_DESC(SYS_PMCNTENCLR_EL0), access_pmcnten, reset_unknown, PMCNTENSET_EL0 },
-	{ SYS_DESC(SYS_PMOVSCLR_EL0), access_pmovs, reset_unknown, PMOVSSET_EL0 },
-	{ SYS_DESC(SYS_PMSWINC_EL0), access_pmswinc, reset_unknown, PMSWINC_EL0 },
-	{ SYS_DESC(SYS_PMSELR_EL0), access_pmselr, reset_unknown, PMSELR_EL0 },
-	{ SYS_DESC(SYS_PMCEID0_EL0), access_pmceid },
-	{ SYS_DESC(SYS_PMCEID1_EL0), access_pmceid },
-	{ SYS_DESC(SYS_PMCCNTR_EL0), access_pmu_evcntr, reset_unknown, PMCCNTR_EL0 },
-	{ SYS_DESC(SYS_PMXEVTYPER_EL0), access_pmu_evtyper },
-	{ SYS_DESC(SYS_PMXEVCNTR_EL0), access_pmu_evcntr },
+	{ PMU_SYS_REG(SYS_PMCR_EL0), .access = access_pmcr,
+	  .reset = reset_pmcr, .reg = PMCR_EL0 },
+	{ PMU_SYS_REG(SYS_PMCNTENSET_EL0),
+	  .access = access_pmcnten, .reg = PMCNTENSET_EL0 },
+	{ PMU_SYS_REG(SYS_PMCNTENCLR_EL0),
+	  .access = access_pmcnten, .reg = PMCNTENSET_EL0 },
+	{ PMU_SYS_REG(SYS_PMOVSCLR_EL0),
+	  .access = access_pmovs, .reg = PMOVSSET_EL0 },
+	{ PMU_SYS_REG(SYS_PMSWINC_EL0),
+	  .access = access_pmswinc, .reg = PMSWINC_EL0 },
+	{ PMU_SYS_REG(SYS_PMSELR_EL0),
+	  .access = access_pmselr, .reg = PMSELR_EL0 },
+	{ PMU_SYS_REG(SYS_PMCEID0_EL0),
+	  .access = access_pmceid, .reset = NULL },
+	{ PMU_SYS_REG(SYS_PMCEID1_EL0),
+	  .access = access_pmceid, .reset = NULL },
+	{ PMU_SYS_REG(SYS_PMCCNTR_EL0),
+	  .access = access_pmu_evcntr, .reg = PMCCNTR_EL0 },
+	{ PMU_SYS_REG(SYS_PMXEVTYPER_EL0),
+	  .access = access_pmu_evtyper, .reset = NULL },
+	{ PMU_SYS_REG(SYS_PMXEVCNTR_EL0),
+	  .access = access_pmu_evcntr, .reset = NULL },
 	/*
 	 * PMUSERENR_EL0 resets as unknown in 64bit mode while it resets as zero
 	 * in 32bit mode. Here we choose to reset it as zero for consistency.
 	 */
-	{ SYS_DESC(SYS_PMUSERENR_EL0), access_pmuserenr, reset_val, PMUSERENR_EL0, 0 },
-	{ SYS_DESC(SYS_PMOVSSET_EL0), access_pmovs, reset_unknown, PMOVSSET_EL0 },
+	{ PMU_SYS_REG(SYS_PMUSERENR_EL0), .access = access_pmuserenr,
+	  .reset = reset_val, .reg = PMUSERENR_EL0, .val = 0 },
+	{ PMU_SYS_REG(SYS_PMOVSSET_EL0),
+	  .access = access_pmovs, .reg = PMOVSSET_EL0 },
 
 	{ SYS_DESC(SYS_TPIDR_EL0), NULL, reset_unknown, TPIDR_EL0 },
 	{ SYS_DESC(SYS_TPIDRRO_EL0), NULL, reset_unknown, TPIDRRO_EL0 },
@@ -1694,7 +1721,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	 * PMCCFILTR_EL0 resets as unknown in 64bit mode while it resets as zero
 	 * in 32bit mode. Here we choose to reset it as zero for consistency.
 	 */
-	{ SYS_DESC(SYS_PMCCFILTR_EL0), access_pmu_evtyper, reset_val, PMCCFILTR_EL0, 0 },
+	{ PMU_SYS_REG(SYS_PMCCFILTR_EL0), .access = access_pmu_evtyper,
+	  .reset = reset_val, .reg = PMCCFILTR_EL0, .val = 0 },
 
 	{ SYS_DESC(SYS_DACR32_EL2), NULL, reset_unknown, DACR32_EL2 },
 	{ SYS_DESC(SYS_IFSR32_EL2), NULL, reset_unknown, IFSR32_EL2 },