Support for cpuid functions with subleaves

Support for cpuid functions with subleaves

[Amit Shah]

Hello,

v3 of the patch uses the KVM_SET_CPUID2 interface to not cause any userspace
and kernel incompatibilities.

With these patches applied, I can run a VM with a newer CPU type (core2duo).

Fixes bug #2413430

Please apply
Amit

[PATCH] kvm: libkvm: Add a wrapper for an ioctl for the KVM_SET_CPUID2 interface

[Amit Shah]

kvm_set_cpuid2() builds on top of kvm_set_cpuid() and correctly populates
cpuid functions that have sub-leaves.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 libkvm/libkvm-x86.c |   21 +++++++++++++++++++++
 libkvm/libkvm.h     |   16 ++++++++++++++++
 2 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/libkvm/libkvm-x86.c b/libkvm/libkvm-x86.c
index a8cca15..dcef548 100644
--- a/libkvm/libkvm-x86.c
+++ b/libkvm/libkvm-x86.c
@@ -475,6 +475,27 @@ int kvm_setup_cpuid(kvm_context_t kvm, int vcpu, int nent,
 	return r;
 }
 
+int kvm_setup_cpuid2(kvm_context_t kvm, int vcpu, int nent,
+		     struct kvm_cpuid_entry2 *entries)
+{
+	struct kvm_cpuid2 *cpuid;
+	int r;
+
+	cpuid = malloc(sizeof(*cpuid) + nent * sizeof(*entries));
+	if (!cpuid)
+		return -ENOMEM;
+
+	cpuid->nent = nent;
+	memcpy(cpuid->entries, entries, nent * sizeof(*entries));
+	r = ioctl(kvm->vcpu_fd[vcpu], KVM_SET_CPUID2, cpuid);
+	if (r == -1) {
+		fprintf(stderr, "kvm_setup_cpuid2: %m\n");
+		return -errno;
+	}
+	free(cpuid);
+	return r;
+}
+
 int kvm_set_shadow_pages(kvm_context_t kvm, unsigned int nrshadow_pages)
 {
 #ifdef KVM_CAP_MMU_SHADOW_CACHE_CONTROL
diff --git a/libkvm/libkvm.h b/libkvm/libkvm.h
index ee1ba68..5728b1c 100644
--- a/libkvm/libkvm.h
+++ b/libkvm/libkvm.h
@@ -373,6 +373,22 @@ int kvm_setup_cpuid(kvm_context_t kvm, int vcpu, int nent,
 		    struct kvm_cpuid_entry *entries);
 
 /*!
+ * \brief Setup a vcpu's cpuid instruction emulation
+ *
+ * Set up a table of cpuid function to cpuid outputs.
+ * This call replaces the older kvm_setup_cpuid interface by adding a few
+ * parameters to support cpuid functions that have sub-leaf values.
+ *
+ * \param kvm Pointer to the current kvm_context
+ * \param vcpu Which virtual CPU should be initialized
+ * \param nent number of entries to be installed
+ * \param entries cpuid function entries table
+ * \return 0 on success, or -errno on error
+ */
+int kvm_setup_cpuid2(kvm_context_t kvm, int vcpu, int nent,
+		     struct kvm_cpuid_entry2 *entries);
+
+/*!
  * \brief Setting the number of shadow pages to be allocated to the vm
  *
  * \param kvm pointer to kvm_context
-- 
1.6.0.6

[PATCH] kvm: userspace: Fetch sub-leaf cpuid values for functions 4, 0xb, 0xd.

[Amit Shah]

CPUID functions 4, 0xb and 0xd have sub-leaf values which depend on the
input value of ECX. Fetch these cpuid values and pass them on to the kernel.

We also switch to the kvm_set_cpuid2() ioctl for this; kvm_set_cpuid() can't
handle the extra parameters we need to support sub-leaves.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 qemu/qemu-kvm-x86.c |   37 ++++++++++++++++++++++++++++---------
 1 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/qemu/qemu-kvm-x86.c b/qemu/qemu-kvm-x86.c
index 4fad2af..52ddd33 100644
--- a/qemu/qemu-kvm-x86.c
+++ b/qemu/qemu-kvm-x86.c
@@ -462,10 +462,11 @@ void kvm_arch_save_regs(CPUState *env)
     }
 }
 
-static void do_cpuid_ent(struct kvm_cpuid_entry *e, uint32_t function,
-			 CPUState *env)
+static void do_cpuid_ent(struct kvm_cpuid_entry2 *e, uint32_t function,
+                         uint32_t count, CPUState *env)
 {
     env->regs[R_EAX] = function;
+    env->regs[R_ECX] = count;
     qemu_kvm_cpuid_on_env(env);
     e->function = function;
     e->eax = env->regs[R_EAX];
@@ -507,14 +508,14 @@ static int get_para_features(kvm_context_t kvm_context)
 
 int kvm_arch_qemu_init_env(CPUState *cenv)
 {
-    struct kvm_cpuid_entry cpuid_ent[100];
+    struct kvm_cpuid_entry2 cpuid_ent[100];
 #ifdef KVM_CPUID_SIGNATURE
-    struct kvm_cpuid_entry *pv_ent;
+    struct kvm_cpuid_entry2 *pv_ent;
     uint32_t signature[3];
 #endif
     int cpuid_nent = 0;
     CPUState copy;
-    uint32_t i, limit;
+    uint32_t i, j, limit;
 
     copy = *cenv;
 
@@ -539,17 +540,35 @@ int kvm_arch_qemu_init_env(CPUState *cenv)
     qemu_kvm_cpuid_on_env(&copy);
     limit = copy.regs[R_EAX];
 
-    for (i = 0; i <= limit; ++i)
-	do_cpuid_ent(&cpuid_ent[cpuid_nent++], i, &copy);
+    for (i = 0; i <= limit; ++i) {
+        if (i == 4 || i == 0xb || i == 0xd) {
+            for (j = 0; ; ++j) {
+                do_cpuid_ent(&cpuid_ent[cpuid_nent], i, j, &copy);
+
+                cpuid_ent[cpuid_nent].flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+                cpuid_ent[cpuid_nent].index = j;
+
+                cpuid_nent++;
+
+                if (i == 4 && copy.regs[R_EAX] == 0)
+                    break;
+                if (i == 0xb && !(copy.regs[R_ECX] & 0xff00))
+                    break;
+                if (i == 0xd && copy.regs[R_EAX] == 0)
+                    break;
+            }
+        } else
+            do_cpuid_ent(&cpuid_ent[cpuid_nent++], i, 0, &copy);
+    }
 
     copy.regs[R_EAX] = 0x80000000;
     qemu_kvm_cpuid_on_env(&copy);
     limit = copy.regs[R_EAX];
 
     for (i = 0x80000000; i <= limit; ++i)
-	do_cpuid_ent(&cpuid_ent[cpuid_nent++], i, &copy);
+	do_cpuid_ent(&cpuid_ent[cpuid_nent++], i, 0, &copy);
 
-    kvm_setup_cpuid(kvm_context, cenv->cpu_index, cpuid_nent, cpuid_ent);
+    kvm_setup_cpuid2(kvm_context, cenv->cpu_index, cpuid_nent, cpuid_ent);
     return 0;
 }
 
-- 
1.6.0.6

Re: Support for cpuid functions with subleaves

[Avi Kivity]

Amit Shah wrote:
> Hello,
>
> v3 of the patch uses the KVM_SET_CPUID2 interface to not cause any userspace
> and kernel incompatibilities.
>
> With these patches applied, I can run a VM with a newer CPU type (core2duo).
>
> Fixes bug #2413430
>
> Please apply
>   

Applied both, thanks.

-- 
error compiling committee.c: too many arguments to function

Support for cpuid functions with subleaves

[Amit Shah]

These patches add support for handling sub-leaf values of some cpuid functions.

The kernel patch updates a userspace-visible for a typo. That value is not
yet used in the userspace so this should be harmless.

With these patches, a VM with the core2duo cpu type boots successfully.

Amit.