[PATCH v4 7/9] target/arm/kvm: scratch vcpu: Preserve input kvm_vcpu_init features

[Andrew Jones <drjones@redhat.com>]

kvm_arm_create_scratch_host_vcpu() takes a struct kvm_vcpu_init
parameter. Rather than just using it as an output parameter to
pass back the preferred target, use it also as an input parameter,
allowing a caller to pass a selected target if they wish and to
also pass cpu features. If the caller doesn't want to select a
target they can pass -1 for the target which indicates they want
to use the preferred target and have it passed back like before.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
 target/arm/kvm.c   | 20 +++++++++++++++-----
 target/arm/kvm32.c |  6 +++++-
 target/arm/kvm64.c |  6 +++++-
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 72569f71236e..7a540d9591f9 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -66,7 +66,7 @@ bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
                                       int *fdarray,
                                       struct kvm_vcpu_init *init)
 {
-    int ret, kvmfd = -1, vmfd = -1, cpufd = -1;
+    int ret = 0, kvmfd = -1, vmfd = -1, cpufd = -1;
 
     kvmfd = qemu_open("/dev/kvm", O_RDWR);
     if (kvmfd < 0) {
@@ -86,7 +86,14 @@ bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
         goto finish;
     }
 
-    ret = ioctl(vmfd, KVM_ARM_PREFERRED_TARGET, init);
+    if (init->target == -1) {
+        struct kvm_vcpu_init preferred;
+
+        ret = ioctl(vmfd, KVM_ARM_PREFERRED_TARGET, &preferred);
+        if (!ret) {
+            init->target = preferred.target;
+        }
+    }
     if (ret >= 0) {
         ret = ioctl(cpufd, KVM_ARM_VCPU_INIT, init);
         if (ret < 0) {
@@ -98,10 +105,12 @@ bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
          * creating one kind of guest CPU which is its preferred
          * CPU type.
          */
+        struct kvm_vcpu_init try;
+
         while (*cpus_to_try != QEMU_KVM_ARM_TARGET_NONE) {
-            init->target = *cpus_to_try++;
-            memset(init->features, 0, sizeof(init->features));
-            ret = ioctl(cpufd, KVM_ARM_VCPU_INIT, init);
+            try.target = *cpus_to_try++;
+            memcpy(try.features, init->features, sizeof(init->features));
+            ret = ioctl(cpufd, KVM_ARM_VCPU_INIT, &try);
             if (ret >= 0) {
                 break;
             }
@@ -109,6 +118,7 @@ bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
         if (ret < 0) {
             goto err;
         }
+        init->target = try.target;
     } else {
         /* Treat a NULL cpus_to_try argument the same as an empty
          * list, which means we will fail the call since this must
diff --git a/target/arm/kvm32.c b/target/arm/kvm32.c
index 2451a2d4bbef..32bf8d6757c4 100644
--- a/target/arm/kvm32.c
+++ b/target/arm/kvm32.c
@@ -53,7 +53,11 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         QEMU_KVM_ARM_TARGET_CORTEX_A15,
         QEMU_KVM_ARM_TARGET_NONE
     };
-    struct kvm_vcpu_init init;
+    /*
+     * target = -1 informs kvm_arm_create_scratch_host_vcpu()
+     * to use the preferred target
+     */
+    struct kvm_vcpu_init init = { .target = -1, };
 
     if (!kvm_arm_create_scratch_host_vcpu(cpus_to_try, fdarray, &init)) {
         return false;
diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
index fc62bab8684e..f96649ae0349 100644
--- a/target/arm/kvm64.c
+++ b/target/arm/kvm64.c
@@ -502,7 +502,11 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         KVM_ARM_TARGET_CORTEX_A57,
         QEMU_KVM_ARM_TARGET_NONE
     };
-    struct kvm_vcpu_init init;
+    /*
+     * target = -1 informs kvm_arm_create_scratch_host_vcpu()
+     * to use the preferred target
+     */
+    struct kvm_vcpu_init init = { .target = -1, };
 
     if (!kvm_arm_create_scratch_host_vcpu(cpus_to_try, fdarray, &init)) {
         return false;
-- 
2.20.1