[Qemu-devel] [PATCH 1/3] expose paravirt feature list to cpuid

[Glauber Costa <glommer@redhat.com>]

Expose the paravirt features provided by the host to the guest.
The features exposed uses qemu just as a medium, since they only
depend on a negotiation between the host and guest directly.

As a direct result, we're now able to run the kvm pvclock in qemu
based kvm guests.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 kvm.h             |    1 +
 target-i386/kvm.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/kvm.h b/kvm.h
index efce145..db58baa 100644
--- a/kvm.h
+++ b/kvm.h
@@ -17,6 +17,7 @@
 #include "config.h"
 
 #ifdef CONFIG_KVM
+#include <linux/kvm_para.h>
 extern int kvm_allowed;
 
 #define kvm_enabled() (kvm_allowed)
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 2412ae4..7f4e5aa 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -33,16 +33,61 @@
     do { } while (0)
 #endif
 
+struct kvm_para_features {
+    int cap;
+    int feature;
+} para_features[] = {
+#ifdef KVM_CAP_CLOCKSOURCE
+	{ KVM_CAP_CLOCKSOURCE, KVM_FEATURE_CLOCKSOURCE },
+#endif
+#ifdef KVM_CAP_NOP_IO_DELAY
+	{ KVM_CAP_NOP_IO_DELAY, KVM_FEATURE_NOP_IO_DELAY },
+#endif
+#ifdef KVM_CAP_PV_MMU
+	{ KVM_CAP_PV_MMU, KVM_FEATURE_MMU_OP },
+#endif
+#ifdef KVM_CAP_CR3_CACHE
+	{ KVM_CAP_CR3_CACHE, KVM_FEATURE_CR3_CACHE },
+#endif
+};
+
+static uint32_t get_para_features(CPUState *env)
+{
+    uint32_t i, features = 0;
+
+    for (i = 0; i < ARRAY_SIZE(para_features); i++) {
+        if (kvm_ioctl(env->kvm_state, KVM_CHECK_EXTENSION, para_features[i].cap))
+            features |= (1 << para_features[i].feature);
+    }
+
+    return features;
+}
 int kvm_arch_init_vcpu(CPUState *env)
 {
     struct {
         struct kvm_cpuid cpuid;
         struct kvm_cpuid_entry entries[100];
     } __attribute__((packed)) cpuid_data;
-    uint32_t limit, i, cpuid_i;
+    uint32_t limit, i, cpuid_i = 0;
     uint32_t eax, ebx, ecx, edx;
+#ifdef KVM_CPUID_SIGNATURE
+    struct kvm_cpuid_entry *pv_ent;
+
+    /* Paravirtualization CPUIDs */
+    pv_ent = &cpuid_data.entries[cpuid_i++];
+    memset(pv_ent, 0, sizeof(*pv_ent));
+    pv_ent->function = KVM_CPUID_SIGNATURE;
+    pv_ent->eax = 0;
+    pv_ent->ebx = 0x4b4d564b; /* KVMKVMK */
+    pv_ent->ecx = 0x564b4d56; /* VMKV */
+    pv_ent->edx = 0x0000004d; /* M */
+
+    pv_ent = &cpuid_data.entries[cpuid_i++];
+    memset(pv_ent, 0, sizeof(*pv_ent));
+    pv_ent->function = KVM_CPUID_FEATURES;
+    pv_ent->eax = get_para_features(env);
+#endif
 
-    cpuid_i = 0;
 
     cpu_x86_cpuid(env, 0, &eax, &ebx, &ecx, &edx);
     limit = eax;
-- 
1.5.6.5