[PATCH v10 21/26] target/arm/cpu64: Add helper to test SYSREG props against a scratch vcpu

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

Add kvm_idreg_write_scratch_vcpu helper that will be used
by qmp_query_cpu_model_expansion code to test SYSREG settings
against a scratch vcpu. Indeed when the expansion code is called
the actual vcpu has not been initialized so we use a scratch vcpu.
This latter has been initialized with features taken from
legacy compositive options (EL2, SVE, ...). So the trial is
very close to the final setup.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 target/arm/kvm_arm.h    |  4 ++++
 target/arm/kvm-stub.c   |  7 +++++++
 target/arm/kvm.c        | 21 +++++++++++++++++++++
 target/arm/trace-events |  1 +
 4 files changed, 33 insertions(+)

diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index e7c40fb003..25a1dec095 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -14,6 +14,7 @@
 #include "qapi/qapi-types-misc-arm.h"
 #include "system/kvm.h"
 #include "target/arm/cpu-qom.h"
+#include "cpu-idregs.h"
 
 #define KVM_ARM_VGIC_V2   (1 << 0)
 #define KVM_ARM_VGIC_V3   (1 << 1)
@@ -240,4 +241,7 @@ void arm_gic_cap_kvm_probe(GICCapability *v2, GICCapability *v3);
  */
 char *kvm_print_register_name(uint64_t regidx);
 
+bool kvm_idreg_write_scratch_vcpu(ARMCPU *cpu, int cpufd,
+                                  ARM64SysRegField *field, uint64_t newfv,
+                                  Error **errp);
 #endif
diff --git a/target/arm/kvm-stub.c b/target/arm/kvm-stub.c
index 88cbe8d85c..8e6fae0a4d 100644
--- a/target/arm/kvm-stub.c
+++ b/target/arm/kvm-stub.c
@@ -119,3 +119,10 @@ char *kvm_print_register_name(uint64_t regidx)
 {
     g_assert_not_reached();
 }
+
+bool kvm_idreg_write_scratch_vcpu(ARMCPU *cpu, int cpufd,
+                                  ARM64SysRegField *field, uint64_t newfv,
+                                  Error **errp)
+{
+    g_assert_not_reached();
+}
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 0c7e80aea8..82ffcac7e3 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -1297,6 +1297,27 @@ static int kvm_arm_apply_one_sysreg_prop(ARMCPU *cpu, ARM64SysRegField *field,
     return kvm_arm_override_idreg_field(CPU(cpu)->kvm_fd, field, newfv, errp);
 }
 
+bool kvm_idreg_write_scratch_vcpu(ARMCPU *cpu, int cpufd,
+                                  ARM64SysRegField *field, uint64_t newfv,
+                                  Error **errp)
+{
+    int ret;
+
+    if (!arm_cpu_validate_sysreg_prop(cpu, field, newfv, errp)) {
+        return false;
+    }
+
+    ret = kvm_arm_override_idreg_field(cpufd, field, newfv, errp);
+    if (ret) {
+        return false;
+    }
+
+    cpu->isar.idregs[field->index] =
+        deposit64(cpu->isar.idregs[field->index],
+                  field->shift, field->length, newfv);
+    return true;
+}
+
 static int kvm_arm_apply_sysreg_props(ARMCPU *cpu, Error **errp)
 {
     return arm_cpu_apply_sysreg_props(cpu, kvm_arm_apply_one_sysreg_prop, errp);
diff --git a/target/arm/trace-events b/target/arm/trace-events
index 81564f1d96..a731b5d4ba 100644
--- a/target/arm/trace-events
+++ b/target/arm/trace-events
@@ -15,6 +15,7 @@ arm_gt_update_irq(int timer, int irqstate) "gt_update_irq: timer %d irqstate %d"
 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_override_idreg_field(const char *reg_name, const char *field_name, uint64_t currentfv, uint64_t newfv) "%s.%s current=0x%"PRIx64" new=0x%"PRIx64
+kvm_arm_idreg_write_scratch_vcpu(const char *name, uint64_t oldfv, uint64_t newfv, uint64_t actualfv) "successful dry-run for %s old=0x%"PRIx64" new=0x%"PRIx64" actual=0x%"PRIx64
 
 # cpu.c
 arm_cpu_reset(uint64_t mp_aff) "cpu %" PRIu64
-- 
2.53.0