[Qemu-devel] [PATCH 0/4] Fix kvm cpuid reporting

[Qemu-devel] [PATCH 0/4] Fix kvm cpuid reporting

[Avi Kivity]

kvm supports an interface for reporting which cpuid features are supported.
Use it for trimming the cpu feature set reported to the guest.  This prevents,
for example, reporting NX to a guest when in fact we do not support it.

Avi Kivity (4):
  kvm: Add support for querying supported cpu features
  Make x86 cpuid feature names available in file scope
  Fix x86 feature modifications for features that set multiple bits
  kvm: Trim cpu features not supported by kvm

 kvm.h                |    3 ++
 target-i386/helper.c |   98 +++++++++++++++++++++++++++++++++----------------
 target-i386/kvm.c    |   80 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 149 insertions(+), 32 deletions(-)

[Qemu-devel] [PATCH 1/4] kvm: Add support for querying supported cpu features

[Avi Kivity]

kvm does not support all cpu features; add support for dunamically querying
the supported feature set.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 kvm.h             |    3 ++
 target-i386/kvm.c |   80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 0 deletions(-)

diff --git a/kvm.h b/kvm.h
index bd4e8d4..c134c45 100644
--- a/kvm.h
+++ b/kvm.h
@@ -124,6 +124,9 @@ void kvm_arch_remove_all_hw_breakpoints(void);
 
 void kvm_arch_update_guest_debug(CPUState *env, struct kvm_guest_debug *dbg);
 
+uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function,
+                                      int reg);
+
 /* generic hooks - to be moved/refactored once there are more users */
 
 static inline void cpu_synchronize_state(CPUState *env, int modified)
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index b534b2d..5f54ff5 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -34,6 +34,86 @@
     do { } while (0)
 #endif
 
+#ifdef KVM_CAP_EXT_CPUID
+
+static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int max)
+{
+    struct kvm_cpuid2 *cpuid;
+    int r, size;
+
+    size = sizeof(*cpuid) + max * sizeof(*cpuid->entries);
+    cpuid = (struct kvm_cpuid2 *)qemu_mallocz(size);
+    cpuid->nent = max;
+    r = kvm_ioctl(s, KVM_GET_SUPPORTED_CPUID, cpuid);
+    if (r < 0) {
+        if (r == -E2BIG) {
+            qemu_free(cpuid);
+            return NULL;
+        } else {
+            fprintf(stderr, "KVM_GET_SUPPORTED_CPUID failed: %s\n",
+                    strerror(-r));
+            exit(1);
+        }
+    }
+    return cpuid;
+}
+
+uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function, int reg)
+{
+    struct kvm_cpuid2 *cpuid;
+    int i, max;
+    uint32_t ret = 0;
+    uint32_t cpuid_1_edx;
+
+    if (!kvm_check_extension(KVM_CAP_EXT_CPUID)) {
+        return -1U;
+    }
+
+    max = 1;
+    while ((cpuid = try_get_cpuid(env->kvm_state, max)) == NULL) {
+        max *= 2;
+    }
+
+    for (i = 0; i < cpuid->nent; ++i) {
+        if (cpuid->entries[i].function == function) {
+            switch (reg) {
+            case R_EAX:
+                ret = cpuid->entries[i].eax;
+                break;
+            case R_EBX:
+                ret = cpuid->entries[i].ebx;
+                break;
+            case R_ECX:
+                ret = cpuid->entries[i].ecx;
+                break;
+            case R_EDX:
+                ret = cpuid->entries[i].edx;
+                if (function == 0x80000001) {
+                    /* On Intel, kvm returns cpuid according to the Intel spec,
+                     * so add missing bits according to the AMD spec:
+                     */
+                    cpuid_1_edx = kvm_arch_get_supported_cpuid(env, 1, R_EDX);
+                    ret |= cpuid_1_edx & 0xdfeff7ff;
+                }
+                break;
+            }
+        }
+    }
+
+    qemu_free(cpuid);
+
+    return ret;
+}
+
+#else
+
+uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function, int reg)
+{
+    return -1U;
+}
+
+#endif
+
 int kvm_arch_init_vcpu(CPUState *env)
 {
     struct {
-- 
1.6.1.1

[Qemu-devel] Re: [PATCH 1/4] kvm: Add support for querying supported cpu features

[Anthony Liguori]

Avi Kivity wrote:
> kvm does not support all cpu features; add support for dunamically querying
> the supported feature set.
>
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  kvm.h             |    3 ++
>  target-i386/kvm.c |   80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 83 insertions(+), 0 deletions(-)
>
> diff --git a/kvm.h b/kvm.h
> index bd4e8d4..c134c45 100644
> --- a/kvm.h
> +++ b/kvm.h
> @@ -124,6 +124,9 @@ void kvm_arch_remove_all_hw_breakpoints(void);
>  
>  void kvm_arch_update_guest_debug(CPUState *env, struct kvm_guest_debug *dbg);
>  
> +uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function,
> +                                      int reg);
> +
>  /* generic hooks - to be moved/refactored once there are more users */
>  
>  static inline void cpu_synchronize_state(CPUState *env, int modified)
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index b534b2d..5f54ff5 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -34,6 +34,86 @@
>      do { } while (0)
>  #endif
>  
> +#ifdef KVM_CAP_EXT_CPUID
> +
> +static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int max)
> +{
> +    struct kvm_cpuid2 *cpuid;
> +    int r, size;
> +
> +    size = sizeof(*cpuid) + max * sizeof(*cpuid->entries);
> +    cpuid = (struct kvm_cpuid2 *)qemu_mallocz(size);
> +    cpuid->nent = max;
> +    r = kvm_ioctl(s, KVM_GET_SUPPORTED_CPUID, cpuid);
> +    if (r < 0) {
> +        if (r == -E2BIG) {
> +            qemu_free(cpuid);
> +            return NULL;
> +        } else {
> +            fprintf(stderr, "KVM_GET_SUPPORTED_CPUID failed: %s\n",
> +                    strerror(-r));
> +            exit(1);
> +        }
> +    }
> +    return cpuid;
> +}
> +
> +uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function, int reg)
> +{
> +    struct kvm_cpuid2 *cpuid;
> +    int i, max;
> +    uint32_t ret = 0;
> +    uint32_t cpuid_1_edx;
> +
> +    if (!kvm_check_extension(KVM_CAP_EXT_CPUID)) {
> +        return -1U;
> +    

kvm_check_extension doesn't exist in upstream QEMU.  It's a good idea 
though so I added it in a previous commit.  However, I changed the 
signature to it to take a KVMState * as the first argument (which is 
available in env->kvm_state).  I updated this patch to pass the extra 
's' parameter.

Regards,

Anthony Liguori


-- 
Regards,

Anthony Liguori

[Qemu-devel] Re: [PATCH 1/4] kvm: Add support for querying supported cpu features

[Anthony Liguori]

Anthony Liguori wrote:
>
> kvm_check_extension doesn't exist in upstream QEMU.  It's a good idea 
> though so I added it in a previous commit.  However, I changed the 
> signature to it to take a KVMState * as the first argument (which is 
> available in env->kvm_state).  I updated this patch to pass the extra 
> 's' parameter.

Ah, you had a patch, I just didn't notice in my queue.

Still wanted to make the KVMState change though.

-- 
Regards,

Anthony Liguori

[Qemu-devel] Re: [PATCH 1/4] kvm: Add support for querying supported cpu features

[Avi Kivity]

Anthony Liguori wrote:
> Anthony Liguori wrote:
>>
>> kvm_check_extension doesn't exist in upstream QEMU.  It's a good idea 
>> though so I added it in a previous commit.  However, I changed the 
>> signature to it to take a KVMState * as the first argument (which is 
>> available in env->kvm_state).  I updated this patch to pass the extra 
>> 's' parameter.
>
> Ah, you had a patch, I just didn't notice in my queue.
>

Yeah, I should have made the dependency explicit.

> Still wanted to make the KVMState change though.
>

I think the KVM_REQUIRE_EXTENSION bit didn't like it.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

[Qemu-devel] [PATCH 2/4] Make x86 cpuid feature names available in file scope

[Avi Kivity]

To be used later.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 target-i386/helper.c |   55 +++++++++++++++++++++++++------------------------
 1 files changed, 28 insertions(+), 27 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index a070e08..88585b8 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -32,39 +32,40 @@
 
 //#define DEBUG_MMU
 
+/* feature flags taken from "Intel Processor Identification and the CPUID
+ * Instruction" and AMD's "CPUID Specification". In cases of disagreement
+ * about feature names, the Linux name is used. */
+static const char *feature_name[] = {
+    "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
+    "cx8", "apic", NULL, "sep", "mtrr", "pge", "mca", "cmov",
+    "pat", "pse36", "pn" /* Intel psn */, "clflush" /* Intel clfsh */, NULL, "ds" /* Intel dts */, "acpi", "mmx",
+    "fxsr", "sse", "sse2", "ss", "ht" /* Intel htt */, "tm", "ia64", "pbe",
+};
+static const char *ext_feature_name[] = {
+    "pni" /* Intel,AMD sse3 */, NULL, NULL, "monitor", "ds_cpl", "vmx", NULL /* Linux smx */, "est",
+    "tm2", "ssse3", "cid", NULL, NULL, "cx16", "xtpr", NULL,
+    NULL, NULL, "dca", NULL, NULL, NULL, NULL, "popcnt",
+       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+};
+static const char *ext2_feature_name[] = {
+    "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
+    "cx8" /* AMD CMPXCHG8B */, "apic", NULL, "syscall", "mtrr", "pge", "mca", "cmov",
+    "pat", "pse36", NULL, NULL /* Linux mp */, "nx" /* Intel xd */, NULL, "mmxext", "mmx",
+    "fxsr", "fxsr_opt" /* AMD ffxsr */, "pdpe1gb" /* AMD Page1GB */, "rdtscp", NULL, "lm" /* Intel 64 */, "3dnowext", "3dnow",
+};
+static const char *ext3_feature_name[] = {
+    "lahf_lm" /* AMD LahfSahf */, "cmp_legacy", "svm", "extapic" /* AMD ExtApicSpace */, "cr8legacy" /* AMD AltMovCr8 */, "abm", "sse4a", "misalignsse",
+    "3dnowprefetch", "osvw", NULL /* Linux ibs */, NULL, "skinit", "wdt", NULL, NULL,
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+};
+
 static void add_flagname_to_bitmaps(char *flagname, uint32_t *features, 
                                     uint32_t *ext_features, 
                                     uint32_t *ext2_features, 
                                     uint32_t *ext3_features)
 {
     int i;
-    /* feature flags taken from "Intel Processor Identification and the CPUID
-     * Instruction" and AMD's "CPUID Specification". In cases of disagreement 
-     * about feature names, the Linux name is used. */
-    static const char *feature_name[] = {
-        "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
-        "cx8", "apic", NULL, "sep", "mtrr", "pge", "mca", "cmov",
-        "pat", "pse36", "pn" /* Intel psn */, "clflush" /* Intel clfsh */, NULL, "ds" /* Intel dts */, "acpi", "mmx",
-        "fxsr", "sse", "sse2", "ss", "ht" /* Intel htt */, "tm", "ia64", "pbe",
-    };
-    static const char *ext_feature_name[] = {
-       "pni" /* Intel,AMD sse3 */, NULL, NULL, "monitor", "ds_cpl", "vmx", NULL /* Linux smx */, "est",
-       "tm2", "ssse3", "cid", NULL, NULL, "cx16", "xtpr", NULL,
-       NULL, NULL, "dca", NULL, NULL, NULL, NULL, "popcnt",
-       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
-    };
-    static const char *ext2_feature_name[] = {
-       "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
-       "cx8" /* AMD CMPXCHG8B */, "apic", NULL, "syscall", "mtrr", "pge", "mca", "cmov",
-       "pat", "pse36", NULL, NULL /* Linux mp */, "nx" /* Intel xd */, NULL, "mmxext", "mmx",
-       "fxsr", "fxsr_opt" /* AMD ffxsr */, "pdpe1gb" /* AMD Page1GB */, "rdtscp", NULL, "lm" /* Intel 64 */, "3dnowext", "3dnow",
-    };
-    static const char *ext3_feature_name[] = {
-       "lahf_lm" /* AMD LahfSahf */, "cmp_legacy", "svm", "extapic" /* AMD ExtApicSpace */, "cr8legacy" /* AMD AltMovCr8 */, "abm", "sse4a", "misalignsse",
-       "3dnowprefetch", "osvw", NULL /* Linux ibs */, NULL, "skinit", "wdt", NULL, NULL,
-       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
-       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
-    };
 
     for ( i = 0 ; i < 32 ; i++ ) 
         if (feature_name[i] && !strcmp (flagname, feature_name[i])) {
-- 
1.6.1.1

[Qemu-devel] [PATCH 3/4] Fix x86 feature modifications for features that set multiple bits

[Avi Kivity]

QEMU allows adding or removing cpu features by using the syntax '-cpu +feature'
or '-cpu -feature'.  Some cpuid features cause more than one bit to be set or
cleared; but QEMU stops after just one bit has been modified, causing the
feature bits to be inconsistent.

Fix by allowing all feature bits corresponding to a given name to be set.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 target-i386/helper.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 88585b8..0c91133 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -66,28 +66,31 @@ static void add_flagname_to_bitmaps(char *flagname, uint32_t *features,
                                     uint32_t *ext3_features)
 {
     int i;
+    int found = 0;
 
     for ( i = 0 ; i < 32 ; i++ ) 
         if (feature_name[i] && !strcmp (flagname, feature_name[i])) {
             *features |= 1 << i;
-            return;
+            found = 1;
         }
     for ( i = 0 ; i < 32 ; i++ ) 
         if (ext_feature_name[i] && !strcmp (flagname, ext_feature_name[i])) {
             *ext_features |= 1 << i;
-            return;
+            found = 1;
         }
     for ( i = 0 ; i < 32 ; i++ ) 
         if (ext2_feature_name[i] && !strcmp (flagname, ext2_feature_name[i])) {
             *ext2_features |= 1 << i;
-            return;
+            found = 1;
         }
     for ( i = 0 ; i < 32 ; i++ ) 
         if (ext3_feature_name[i] && !strcmp (flagname, ext3_feature_name[i])) {
             *ext3_features |= 1 << i;
-            return;
+            found = 1;
         }
-    fprintf(stderr, "CPU feature %s not found\n", flagname);
+    if (!found) {
+        fprintf(stderr, "CPU feature %s not found\n", flagname);
+    }
 }
 
 typedef struct x86_def_t {
-- 
1.6.1.1

[Qemu-devel] [PATCH 4/4] kvm: Trim cpu features not supported by kvm

[Avi Kivity]

Remove cpu features that are not supported by kvm from the cpuid features
reported to the guest.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 target-i386/helper.c |   30 ++++++++++++++++++++++++++++++
 1 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 0c91133..bdf242b 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -93,6 +93,21 @@ static void add_flagname_to_bitmaps(char *flagname, uint32_t *features,
     }
 }
 
+static void kvm_trim_features(uint32_t *features, uint32_t supported,
+                              const char *names[])
+{
+    int i;
+    uint32_t mask;
+
+    for (i = 0; i < 32; ++i) {
+        mask = 1U << i;
+        if ((*features & mask) && !(supported & mask)) {
+            printf("Processor feature %s not supported by kvm\n", names[i]);
+            *features &= ~mask;
+        }
+    }
+}
+
 typedef struct x86_def_t {
     const char *name;
     uint32_t level;
@@ -1699,5 +1714,20 @@ CPUX86State *cpu_x86_init(const char *cpu_model)
 
     qemu_init_vcpu(env);
 
+    if (kvm_enabled()) {
+        kvm_trim_features(&env->cpuid_features,
+                          kvm_arch_get_supported_cpuid(env, 1, R_EDX),
+                          feature_name);
+        kvm_trim_features(&env->cpuid_ext_features,
+                          kvm_arch_get_supported_cpuid(env, 1, R_ECX),
+                          ext_feature_name);
+        kvm_trim_features(&env->cpuid_ext2_features,
+                          kvm_arch_get_supported_cpuid(env, 0x80000001, R_EDX),
+                          ext2_feature_name);
+        kvm_trim_features(&env->cpuid_ext3_features,
+                          kvm_arch_get_supported_cpuid(env, 0x80000001, R_ECX),
+                          ext3_feature_name);
+    }
+
     return env;
 }
-- 
1.6.1.1

Re: [Qemu-devel] [PATCH 4/4] kvm: Trim cpu features not supported by kvm

[Mark McLoughlin]

On Sun, 2009-05-03 at 17:04 +0300, Avi Kivity wrote:
> Remove cpu features that are not supported by kvm from the cpuid features
> reported to the guest.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
....
> @@ -1699,5 +1714,20 @@ CPUX86State *cpu_x86_init(const char *cpu_model)
>  
>      qemu_init_vcpu(env);
>  
> +    if (kvm_enabled()) {
> +        kvm_trim_features(&env->cpuid_features,
> +                          kvm_arch_get_supported_cpuid(env, 1, R_EDX),
> +                          feature_name);

This isn't work in qemu.git because the features are only queried from
qemu_init_vcpu() (see kvm_arch_init_vcpu())

The obvious fix is to move qemu_init_vcpu() after the feature trimming,
but that requires us to split env->kvm_state initialization out of
kvm_init_vcpu()

Also, it works in qemu-kvm.git, but only because actually call
kvm_qemu_init_env() twice - once before feature trimming and once after.

Cheers,
Mark.