KVM: arm64: Use read-only helper for reading VM ID registers

IDREG() expands to the storage of a particular ID reg, which can be
useful for handling both reads and writes. However, outside of a select
few situations, the ID registers should be considered read only.

Replace current readers with a new macro that expands to the value of
the field rather than the field itself.

Reviewed-by: Sebastian Ott <sebott@redhat.com>
Link: https://lore.kernel.org/r/20240619174036.483943-4-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8170c04fde914c8d09f299f82c9492c8a2afea5b..1201af636551b1d27b3ea949560678584e5a2209 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1332,6 +1332,20 @@ static inline void kvm_hyp_reserve(void) { }
 void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu);
 bool kvm_arm_vcpu_stopped(struct kvm_vcpu *vcpu);
 
+static inline u64 *__vm_id_reg(struct kvm_arch *ka, u32 reg)
+{
+       switch (reg) {
+       case sys_reg(3, 0, 0, 1, 0) ... sys_reg(3, 0, 0, 7, 7):
+               return &ka->id_regs[IDREG_IDX(reg)];
+       default:
+               WARN_ON_ONCE(1);
+               return NULL;
+       }
+}
+
+#define kvm_read_vm_id_reg(kvm, reg)                                   \
+       ({ u64 __val = *__vm_id_reg(&(kvm)->arch, reg); __val; })
+
 #define __expand_field_sign_unsigned(id, fld, val)                     \
        ((u64)SYS_FIELD_VALUE(id, fld, val))
 
@@ -1348,7 +1362,7 @@ bool kvm_arm_vcpu_stopped(struct kvm_vcpu *vcpu);
 
 #define get_idreg_field_unsigned(kvm, id, fld)                         \
        ({                                                              \
-               u64 __val = IDREG((kvm), SYS_##id);                     \
+               u64 __val = kvm_read_vm_id_reg((kvm), SYS_##id);        \
                FIELD_GET(id##_##fld##_MASK, __val);                    \
        })
 

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index a35ce10e0a9f3efe554cbf4b1d11fc2300ed54e4..7848daeafd038eeaf9a83e6b0478953df6fd1ec1 100644 (file)
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -54,7 +54,7 @@ static u32 __kvm_pmu_event_mask(unsigned int pmuver)
 
 static u32 kvm_pmu_event_mask(struct kvm *kvm)
 {
-       u64 dfr0 = IDREG(kvm, SYS_ID_AA64DFR0_EL1);
+       u64 dfr0 = kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1);
        u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, dfr0);
 
        return __kvm_pmu_event_mask(pmuver);

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 1036f865c826556e68b5f18170789fb9f662426a..0692a109fd4d3858545f404744656f038fbd86b0 100644 (file)
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1565,7 +1565,7 @@ static u64 kvm_read_sanitised_id_reg(struct kvm_vcpu *vcpu,
 
 static u64 read_id_reg(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 {
-       return IDREG(vcpu->kvm, reg_to_encoding(r));
+       return kvm_read_vm_id_reg(vcpu->kvm, reg_to_encoding(r));
 }
 
 static bool is_feature_id_reg(u32 encoding)
@@ -2760,7 +2760,7 @@ static bool trap_dbgdidr(struct kvm_vcpu *vcpu,
        if (p->is_write) {
                return ignore_write(vcpu, p);
        } else {
-               u64 dfr = IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1);
+               u64 dfr = kvm_read_vm_id_reg(vcpu->kvm, SYS_ID_AA64DFR0_EL1);
                u32 el3 = kvm_has_feat(vcpu->kvm, ID_AA64PFR0_EL1, EL3, IMP);
 
                p->regval = ((SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr) << 28) |
@@ -3519,7 +3519,7 @@ static int idregs_debug_show(struct seq_file *s, void *v)
                return 0;
 
        seq_printf(s, "%20s:\t%016llx\n",
-                  desc->name, IDREG(kvm, reg_to_encoding(desc)));
+                  desc->name, kvm_read_vm_id_reg(kvm, reg_to_encoding(desc)));
 
        return 0;
 }