[Qemu-devel] [PATCH] kvm: Add helpers for checking and requiring kvm extensions

[Avi Kivity]

Instead of open-coding the check extension sequence, provide helpers
for checking whether an extension exists, and for aborting if an
extension is missing.

Signed-off-by: Avi Kivity <address@hidden>
---
 kvm-all.c         |   63 +++++++++++++++++++++++++++--------------------------
 kvm.h             |    6 +++++
 target-i386/kvm.c |    8 +------
 3 files changed, 39 insertions(+), 38 deletions(-)

diff --git a/kvm-all.c b/kvm-all.c
index 36659a9..1642a2a 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -64,6 +64,30 @@ struct KVMState
 
 static KVMState *kvm_state;
 
+int kvm_check_extension(int extension)
+{
+    int ret;
+
+    ret = kvm_ioctl(kvm_state, KVM_CHECK_EXTENSION, extension);
+    if (ret < 0) {
+        fprintf(stderr, "KVM_CHECK_EXTENSION failed: %s\n", strerror(errno));
+        exit(1);
+    }
+    return ret;
+}
+
+int kvm_require_extension(int extension, const char *estr)
+{
+    int ret;
+
+    ret = kvm_check_extension(extension);
+    if (!ret) {
+        fprintf(stderr, "Required KVM extension %s not present\n", estr);
+        exit(1);
+    }
+    return ret;
+}
+
 static KVMSlot *kvm_alloc_slot(KVMState *s)
 {
     int i;
@@ -331,6 +355,8 @@ int kvm_init(int smp_cpus)
 
     s = qemu_mallocz(sizeof(KVMState));
 
+    kvm_state = s;
+
 #ifdef KVM_CAP_SET_GUEST_DEBUG
     TAILQ_INIT(&s->kvm_sw_breakpoints);
 #endif
@@ -368,42 +394,22 @@ int kvm_init(int smp_cpus)
      * just use a user allocated buffer so we can use regular pages
      * unmodified.  Make sure we have a sufficiently modern version of KVM.
      */
-    ret = kvm_ioctl(s, KVM_CHECK_EXTENSION, KVM_CAP_USER_MEMORY);
-    if (ret <= 0) {
-        if (ret == 0)
-            ret = -EINVAL;
-        fprintf(stderr, "kvm does not support KVM_CAP_USER_MEMORY\n");
-        goto err;
-    }
+    KVM_REQUIRE_EXTENSION(KVM_CAP_USER_MEMORY);
 
     /* There was a nasty bug in < kvm-80 that prevents memory slots from being
      * destroyed properly.  Since we rely on this capability, refuse to work
      * with any kernel without this capability. */
-    ret = kvm_ioctl(s, KVM_CHECK_EXTENSION,
-                    KVM_CAP_DESTROY_MEMORY_REGION_WORKS);
-    if (ret <= 0) {
-        if (ret == 0)
-            ret = -EINVAL;
-
-        fprintf(stderr,
-                "KVM kernel module broken (DESTROY_MEMORY_REGION)\n"
-                "Please upgrade to at least kvm-81.\n");
-        goto err;
-    }
+    KVM_REQUIRE_EXTENSION(KVM_CAP_DESTROY_MEMORY_REGION_WORKS);
 
     s->coalesced_mmio = 0;
 #ifdef KVM_CAP_COALESCED_MMIO
-    ret = kvm_ioctl(s, KVM_CHECK_EXTENSION, KVM_CAP_COALESCED_MMIO);
-    if (ret > 0)
-        s->coalesced_mmio = ret;
+    s->coalesced_mmio = kvm_check_extension(KVM_CAP_COALESCED_MMIO);
 #endif
 
     ret = kvm_arch_init(s, smp_cpus);
     if (ret < 0)
         goto err;
 
-    kvm_state = s;
-
     return 0;
 
 err:
@@ -415,6 +421,8 @@ err:
     }
     qemu_free(s);
 
+    kvm_state = NULL;
+
     return ret;
 }
 
@@ -763,14 +771,7 @@ int kvm_vcpu_ioctl(CPUState *env, int type, ...)
 
 int kvm_has_sync_mmu(void)
 {
-#ifdef KVM_CAP_SYNC_MMU
-    KVMState *s = kvm_state;
-
-    if (kvm_ioctl(s, KVM_CHECK_EXTENSION, KVM_CAP_SYNC_MMU) > 0)
-        return 1;
-#endif
-
-    return 0;
+    return kvm_check_extension(KVM_CAP_SYNC_MMU);
 }
 
 void kvm_setup_guest_memory(void *start, size_t size)
diff --git a/kvm.h b/kvm.h
index 0ea2426..bd4e8d4 100644
--- a/kvm.h
+++ b/kvm.h
@@ -29,6 +29,12 @@ struct kvm_run;
 
 /* external API */
 
+#define KVM_REQUIRE_EXTENSION(extension) \
+    kvm_require_extension(extension, #extension)
+
+int kvm_check_extension(int extension);
+int kvm_require_extension(int extension, const char *estr);
+
 int kvm_init(int smp_cpus);
 
 int kvm_init_vcpu(CPUState *env);
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 2de8b81..b534b2d 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -154,19 +154,13 @@ static int kvm_has_msr_star(CPUState *env)
 
 int kvm_arch_init(KVMState *s, int smp_cpus)
 {
-    int ret;
-
     /* create vm86 tss.  KVM uses vm86 mode to emulate 16-bit code
      * directly.  In order to use vm86 mode, a TSS is needed.  Since this
      * must be part of guest physical memory, we need to allocate it.  Older
      * versions of KVM just assumed that it would be at the end of physical
      * memory but that doesn't work with more than 4GB of memory.  We simply
      * refuse to work with those older versions of KVM. */
-    ret = kvm_ioctl(s, KVM_CHECK_EXTENSION, KVM_CAP_SET_TSS_ADDR);
-    if (ret <= 0) {
-        fprintf(stderr, "kvm does not support KVM_CAP_SET_TSS_ADDR\n");
-        return ret;
-    }
+    KVM_REQUIRE_EXTENSION(KVM_CAP_SET_TSS_ADDR);
 
     /* this address is 3 pages before the bios, and the bios should present
      * as unavaible memory.  FIXME, need to ensure the e820 map deals with
-- 
1.6.1.1