[RFC 17/21] arm/kvm: write back modified ID regs to KVM

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

We want to give a chance to override the value of host ID regs.
In a previous patch we made sure all their values could be fetched
through kvm_get_one_reg() calls before their modification. After
their potential modification we need to make sure we write back
the values through kvm_set_one_reg() calls.

Make sure the cpreg_list is modified with updated values and
transfer those values back to kvm.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 target/arm/kvm.c        | 36 +++++++++++++++++++++++++++++++++++-
 target/arm/trace-events |  1 +
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index a0daf4c382..b63578789d 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -1052,6 +1052,31 @@ void kvm_arm_cpu_post_load(ARMCPU *cpu)
     }
 }
 
+static void kvm_arm_writable_idregs_to_cpreg_list(ARMCPU *cpu)
+{
+    for (int i = 0; i < NR_ID_REGS; i++) {
+        uint64_t writable_mask = cpu->writable_map->regs[i];
+        uint64_t *cpreg;
+
+        if (writable_mask) {
+            uint64_t regidx;
+            uint64_t previous, new;
+            ARM64SysReg *sysregdesc = &arm64_id_regs[i];
+            ARMSysReg *sr = sysregdesc->sysreg;
+
+            regidx = ARM64_SYS_REG(sr->op0, sr->op1, sr->crn, sr->crm, sr->op2);
+            cpreg = kvm_arm_get_cpreg_ptr(cpu, regidx);
+            previous = *cpreg;
+            new = cpu->isar.idregs.regs[i];
+            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;
@@ -2019,7 +2044,16 @@ 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 */
+    kvm_arm_writable_idregs_to_cpreg_list(cpu);
+
+    write_list_to_kvmstate(cpu, 3);
+
+    return 0;
 }
 
 int kvm_arch_destroy_vcpu(CPUState *cs)
diff --git a/target/arm/trace-events b/target/arm/trace-events
index 0df3bfafff..668acf94ab 100644
--- a/target/arm/trace-events
+++ b/target/arm/trace-events
@@ -14,3 +14,4 @@ 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 gost 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
-- 
2.41.0