[RFC 01/21] kvm: kvm_get_writable_id_regs

[Eric Auger <eric.auger@redhat.com>]

From: Cornelia Huck <cohuck@redhat.com>

Add an helper to retrieve the writable id reg bitmask. The
status of the query is stored in the CPU struct so that an
an error, if any, can be reported on vcpu realize().

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
 target/arm/cpu.h     | 19 +++++++++++++++++++
 target/arm/kvm_arm.h |  7 +++++++
 target/arm/kvm.c     | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index d8eb986a04..1493b35d99 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -821,6 +821,19 @@ typedef struct {
     uint32_t map, init, supported;
 } ARMVQMap;
 
+typedef enum ARMIdRegsState {
+    WRITABLE_ID_REGS_UNKNOWN,
+    WRITABLE_ID_REGS_NOT_DISCOVERABLE,
+    WRITABLE_ID_REGS_FAILED,
+    WRITABLE_ID_REGS_AVAIL,
+} ARMIdRegsState;
+
+#define NR_ID_REGS (3 * 8 * 8)
+
+typedef struct IdRegMap {
+    uint64_t regs[NR_ID_REGS];
+} IdRegMap;
+
 /**
  * ARMCPU:
  * @env: #CPUARMState
@@ -960,6 +973,12 @@ struct ArchCPU {
      */
     bool host_cpu_probe_failed;
 
+    /*
+     * state of writable id regs query used to report an error, if any,
+     * on KVM custom vcpu model realize
+     */
+    ARMIdRegsState writable_id_regs;
+
     /* QOM property to indicate we should use the back-compat CNTFRQ default */
     bool backcompat_cntfrq;
 
diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index cfaa0d9bc7..9868065277 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -214,6 +214,8 @@ void kvm_arm_pvtime_init(ARMCPU *cpu, uint64_t ipa);
 
 int kvm_arm_set_irq(int cpu, int irqtype, int irq, int level);
 
+int kvm_arm_get_writable_id_regs(ARMCPU *cpu, IdRegMap *idregmap);
+
 #else
 
 /*
@@ -235,6 +237,11 @@ static inline bool kvm_arm_sve_supported(void)
     return false;
 }
 
+static inline int kvm_arm_get_writable_id_regs(ARMCPU *cpu, IdRegMap *idregmap)
+{
+    return -ENOSYS;
+}
+
 /*
  * These functions should never actually be called without KVM support.
  */
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 70f79eda33..be98f8be18 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -47,6 +47,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
 static bool cap_has_mp_state;
 static bool cap_has_inject_serror_esr;
 static bool cap_has_inject_ext_dabt;
+static int cap_writable_id_regs;
 
 /**
  * ARMHostCPUFeatures: information about the host CPU (identified
@@ -478,6 +479,37 @@ void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
     env->features = arm_host_cpu_features.features;
 }
 
+int kvm_arm_get_writable_id_regs(ARMCPU *cpu, IdRegMap *idregmap)
+{
+    struct reg_mask_range range = {
+        .range = 0, /* up to now only a single range is supported */
+        .addr = (uint64_t)idregmap,
+    };
+    int ret;
+
+    if (!kvm_enabled()) {
+        cpu->writable_id_regs = WRITABLE_ID_REGS_NOT_DISCOVERABLE;
+        return -ENOSYS;
+    }
+
+    cap_writable_id_regs =
+        kvm_check_extension(kvm_state, KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES);
+
+    if (!cap_writable_id_regs ||
+        !(cap_writable_id_regs & (1 << KVM_ARM_FEATURE_ID_RANGE))) {
+        cpu->writable_id_regs = WRITABLE_ID_REGS_NOT_DISCOVERABLE;
+        return -ENOSYS;
+    }
+
+    ret = kvm_vm_ioctl(kvm_state, KVM_ARM_GET_REG_WRITABLE_MASKS, &range);
+    if (ret) {
+        cpu->writable_id_regs = WRITABLE_ID_REGS_FAILED;
+        return ret;
+     }
+    cpu->writable_id_regs = WRITABLE_ID_REGS_AVAIL;
+    return ret;
+}
+
 static bool kvm_no_adjvtime_get(Object *obj, Error **errp)
 {
     return !ARM_CPU(obj)->kvm_adjvtime;
-- 
2.41.0