[PATCH v4 11/17] 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>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
 target/arm/kvm.c        | 59 ++++++++++++++++++++++++++++++++++++++++-
 target/arm/trace-events |  1 +
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 1a9b91bf8a..ca9a7d9439 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -275,6 +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 int idregs_idx_to_kvm_feature_idx(ARMIDRegisterIdx idx)
 {
     ARMSysRegs sysreg = id_register_sysreg[idx];
@@ -1197,6 +1212,39 @@ bool kvm_arm_cpu_post_load(ARMCPU *cpu)
     return true;
 }
 
+static void kvm_arm_writable_idregs_to_cpreg_list(ARMCPU *cpu)
+{
+    if (!cpu->writable_map) {
+        return;
+    }
+    for (int i = 0; i < NR_ID_REG_MASKS; i++) {
+        uint64_t writable_mask = cpu->writable_map->regs[i];
+        uint64_t *cpreg;
+
+        if (writable_mask) {
+            uint64_t previous, new;
+            int idx = kvm_feature_idx_to_idregs_idx(i);
+            ARM64SysReg *sysregdesc;
+            uint32_t sysreg;
+
+            if (idx == -1) {
+                /* sysreg writable, but we don't know it */
+                continue;
+            }
+            sysregdesc = &arm64_id_regs[idx];
+            sysreg = sysregdesc->sysreg;
+            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;
@@ -2148,7 +2196,16 @@ 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, KVM_PUT_FULL_STATE);
+
+    return 0;
 }
 
 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