[PATCH v5 12/18] arm/kvm: write back modified ID regs to KVM

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

In case some ID reg values were overriden after their
initialization in kvm_arm_get_host_cpu_features() we need to
copy the new value stored in isar.idregs array back to the
cpreg_list and then sync the cpreg_list to KVM.

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

---

v4 -> v5:
- only call kvm_arm_writable_idregs_to_cpreg_list and
  write_list_to_kvmstate if writable_map is allocated
- reinitialize the cpreg list after sync (Jinqian)
---
 target/arm/kvm.c        | 69 ++++++++++++++++++++++++++++++++++++++++-
 target/arm/trace-events |  1 +
 2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 92219ee62e..30c5175c68 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -274,6 +274,21 @@ 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 int idregs_idx_to_kvm_feature_idx(ARMIDRegisterIdx idx)
 {
     ARMSysRegs sysreg = id_register_sysreg[idx];
@@ -1189,6 +1204,40 @@ bool kvm_arm_cpu_post_load(ARMCPU *cpu)
     return true;
 }
 
+/*
+ * Copy writable ID regs from isar.idregs[] to cpreg_list
+ * in case their value differs from the original init cpreg value
+ */
+static void kvm_arm_writable_idregs_to_cpreg_list(ARMCPU *cpu)
+{
+    for (int i = 0; i < KVM_ARM_FEATURE_ID_RANGE_SIZE; i++) {
+        uint64_t writable_mask = cpu->writable_map[i];
+
+        if (writable_mask) {
+            int idx = kvm_feature_idx_to_idregs_idx(i);
+            ARM64SysReg *sysregdesc;
+            uint64_t previous, new;
+            uint64_t *cpreg;
+            uint32_t sysreg;
+
+            if (idx == -1) {
+                /* sysreg writable, but we don't know it */
+                continue;
+            }
+            sysregdesc = &arm64_id_regs[idx];
+            sysreg = id_register_sysreg[idx];
+            cpreg = kvm_arm_get_cpreg_ptr(cpu, idregs_sysreg_to_kvm_reg(sysreg));
+            previous = *cpreg;
+            new = cpu->isar.idregs[idx];
+            if (previous != new) {
+                *cpreg = new;
+                trace_kvm_arm_writable_idregs_to_cpreg_list(sysregdesc->name,
+                                                            previous, new);
+            }
+        }
+    }
+}
+
 void kvm_arm_reset_vcpu(ARMCPU *cpu)
 {
     int ret;
@@ -2140,7 +2189,25 @@ int kvm_arch_init_vcpu(CPUState *cs)
     }
     cpu->mp_affinity = mpidr & ARM64_AFFINITY_MASK;
 
-    return kvm_arm_init_cpreg_list(cpu);
+    ret = kvm_arm_init_cpreg_list(cpu);
+    if (ret) {
+        return ret;
+    }
+    /* overwrite writable ID regs with their updated property values */
+    if (cpu->writable_map) {
+        kvm_arm_writable_idregs_to_cpreg_list(cpu);
+        ret = write_list_to_kvmstate(cpu, KVM_PUT_FULL_STATE);
+        if (!ret) {
+            return -1;
+        }
+        /*
+         * modified values may have changed the visibility of some regs,
+         * reinitialize the cpreg_list accordingly
+         */
+         ret = kvm_arm_init_cpreg_list(cpu);
+    }
+
+    return ret;
 }
 
 int kvm_arch_destroy_vcpu(CPUState *cs)
diff --git a/target/arm/trace-events b/target/arm/trace-events
index 8c7faf57c7..c25d2a1191 100644
--- a/target/arm/trace-events
+++ b/target/arm/trace-events
@@ -14,6 +14,7 @@ arm_gt_update_irq(int timer, int irqstate) "gt_update_irq: timer %d irqstate %d"
 # kvm.c
 kvm_arm_fixup_msi_route(uint64_t iova, uint64_t gpa) "MSI iova = 0x%"PRIx64" is translated into 0x%"PRIx64
 get_host_cpu_idregs(const char *name, uint64_t value) "scratch vcpu host value for %s is 0x%"PRIx64
+kvm_arm_writable_idregs_to_cpreg_list(const char *name, uint64_t previous, uint64_t new) "%s overwrite default 0x%"PRIx64" with 0x%"PRIx64
 
 # cpu.c
 arm_cpu_reset(uint64_t mp_aff) "cpu %" PRIu64
-- 
2.53.0