[RFC PATCH v7 10/18] target/arm/kvm: Retrieve writable ID reg map

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

From: Cornelia Huck <cohuck@redhat.com>

Add an helper to retrieve the writable id reg bitmask.

then retrieve the writable_map array and dispatch it in the writable_map
fields of arm64_id_regs[] elements.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

---

v5 -> v6
- use arm64_id_regs[].writable_map
- squashed 2 commits (helper + user)
- removed stub
---
 target/arm/kvm.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index d40a6a9859..d270f9870e 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -28,6 +28,7 @@
 #include "kvm_arm.h"
 #include "cpu.h"
 #include "cpu-sysregs.h"
+#include "cpu-idregs.h"
 #include "trace.h"
 #include "internals.h"
 #include "hw/pci/pci.h"
@@ -51,6 +52,7 @@ 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 bool writable_map_dispatched;
 
 /**
  * ARMHostCPUFeatures: information about the host CPU (identified
@@ -273,6 +275,21 @@ static uint32_t kvm_arm_sve_get_vls(int fd)
     return vls[0] & MAKE_64BIT_MASK(0, ARM_MAX_VQ);
 }
 
+static int kvm_feature_idx_to_idregs_idx(int kidx)
+{
+    int op1, crm, op2;
+    ARMSysRegs sysreg;
+
+    op1 = kidx / 64;
+    if (op1 == 2) {
+        op1 = 3;
+    }
+    crm = (kidx % 64) / 8;
+    op2 = kidx % 8;
+    sysreg = ENCODE_ID_REG(3, op1, 0, crm, op2);
+    return get_sysreg_idx(sysreg);
+}
+
 static void kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
 {
     /* Identify the feature bits corresponding to the host CPU, and
@@ -480,9 +497,53 @@ static void kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     ahcf->features = features;
 }
 
+static int kvm_arm_get_writable_id_regs(uint64_t *idregmap)
+{
+    int cap_writable_id_regs;
+    struct reg_mask_range range = {
+        .range = KVM_ARM_FEATURE_ID_RANGE,
+        .reserved = {0},
+        .addr = (uint64_t)idregmap,
+    };
+
+    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))) {
+        return -ENOSYS;
+    }
+
+    if (kvm_vm_ioctl(kvm_state, KVM_ARM_GET_REG_WRITABLE_MASKS, &range)) {
+        return -errno;
+    }
+    return 0;
+}
+
 void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
 {
     CPUARMState *env = &cpu->env;
+    uint64_t *writable_map;
+
+    writable_map = g_new(uint64_t, KVM_ARM_FEATURE_ID_RANGE_SIZE);
+
+    if (!writable_map_dispatched &&
+        !kvm_arm_get_writable_id_regs(writable_map)) {
+        for (int i = 0; i < KVM_ARM_FEATURE_ID_RANGE_SIZE; i++) {
+            uint64_t mask = writable_map[i];
+
+            if (mask) {
+                int idx = kvm_feature_idx_to_idregs_idx(i);
+
+                if (idx < 0 || idx > ARRAY_SIZE(arm64_id_regs)) {
+                    continue;
+                }
+                arm64_id_regs[idx].writable_mask = mask;
+            }
+        }
+        writable_map_dispatched = true;
+    }
+    g_free(writable_map);
 
     if (!arm_host_cpu_features.dtb_compatible) {
         kvm_arm_get_host_cpu_features(&arm_host_cpu_features);
-- 
2.53.0