6 files changed, 139 insertions, 17 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index a89a5ee0b940..488964414f04 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1122,9 +1122,9 @@ struct kvm_cpuid2 {
         struct kvm_cpuid_entry2 entries[0];
 };
 
-#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX 1
-#define KVM_CPUID_FLAG_STATEFUL_FUNC    2
-#define KVM_CPUID_FLAG_STATE_READ_NEXT  4
+#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX         BIT(0)
+#define KVM_CPUID_FLAG_STATEFUL_FUNC            BIT(1)
+#define KVM_CPUID_FLAG_STATE_READ_NEXT          BIT(2)
 
 struct kvm_cpuid_entry2 {
         __u32 function;
@@ -2684,6 +2684,77 @@ and usually define the validity of a groups of registers. (e.g. one bit
 };
 
 
+4.81 KVM_GET_EMULATED_CPUID
+
+Capability: KVM_CAP_EXT_EMUL_CPUID
+Architectures: x86
+Type: system ioctl
+Parameters: struct kvm_cpuid2 (in/out)
+Returns: 0 on success, -1 on error
+
+struct kvm_cpuid2 {
+        __u32 nent;
+        __u32 flags;
+        struct kvm_cpuid_entry2 entries[0];
+};
+
+The member 'flags' is used for passing flags from userspace.
+
+#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX         BIT(0)
+#define KVM_CPUID_FLAG_STATEFUL_FUNC            BIT(1)
+#define KVM_CPUID_FLAG_STATE_READ_NEXT          BIT(2)
+
+struct kvm_cpuid_entry2 {
+        __u32 function;
+        __u32 index;
+        __u32 flags;
+        __u32 eax;
+        __u32 ebx;
+        __u32 ecx;
+        __u32 edx;
+        __u32 padding[3];
+};
+
+This ioctl returns x86 cpuid features which are emulated by
+kvm.Userspace can use the information returned by this ioctl to query
+which features are emulated by kvm instead of being present natively.
+
+Userspace invokes KVM_GET_EMULATED_CPUID by passing a kvm_cpuid2
+structure with the 'nent' field indicating the number of entries in
+the variable-size array 'entries'. If the number of entries is too low
+to describe the cpu capabilities, an error (E2BIG) is returned. If the
+number is too high, the 'nent' field is adjusted and an error (ENOMEM)
+is returned. If the number is just right, the 'nent' field is adjusted
+to the number of valid entries in the 'entries' array, which is then
+filled.
+
+The entries returned are the set CPUID bits of the respective features
+which kvm emulates, as returned by the CPUID instruction, with unknown
+or unsupported feature bits cleared.
+
+Features like x2apic, for example, may not be present in the host cpu
+but are exposed by kvm in KVM_GET_SUPPORTED_CPUID because they can be
+emulated efficiently and thus not included here.
+
+The fields in each entry are defined as follows:
+
+  function: the eax value used to obtain the entry
+  index: the ecx value used to obtain the entry (for entries that are
+         affected by ecx)
+  flags: an OR of zero or more of the following:
+        KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
+           if the index field is valid
+        KVM_CPUID_FLAG_STATEFUL_FUNC:
+           if cpuid for this function returns different values for successive
+           invocations; there will be several entries with the same function,
+           all with this flag set
+        KVM_CPUID_FLAG_STATE_READ_NEXT:
+           for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
+           the first entry to be read by a cpu
+   eax, ebx, ecx, edx: the values returned by the cpuid instruction for
+         this function/index combination
+
+
 6. Capabilities that can be enabled
 -----------------------------------
 
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 5d9a3033b3d7..d3a87780c70b 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -211,9 +211,9 @@ struct kvm_cpuid_entry2 {
         __u32 padding[3];
 };
 
-#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX 1
-#define KVM_CPUID_FLAG_STATEFUL_FUNC    2
-#define KVM_CPUID_FLAG_STATE_READ_NEXT  4
+#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX         BIT(0)
+#define KVM_CPUID_FLAG_STATEFUL_FUNC            BIT(1)
+#define KVM_CPUID_FLAG_STATE_READ_NEXT          BIT(2)
 
 /* for KVM_SET_CPUID2 */
 struct kvm_cpuid2 {
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 0a1e3b8b964d..78a4439bfdc5 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -219,8 +219,14 @@ static bool supported_xcr0_bit(unsigned bit)
 
 #define F(x) bit(X86_FEATURE_##x)
 
-static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
-                         u32 index, int *nent, int maxnent)
+static int __do_cpuid_ent_emulated(struct kvm_cpuid_entry2 *entry,
+                                   u32 func, u32 index, int *nent, int maxnent)
+{
+        return 0;
+}
+
+static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
+                                 u32 index, int *nent, int maxnent)
 {
         int r;
         unsigned f_nx = is_efer_nx() ? F(NX) : 0;
@@ -515,6 +521,15 @@ out:
         return r;
 }
 
+static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 func,
+                        u32 idx, int *nent, int maxnent, unsigned int type)
+{
+        if (type == KVM_GET_EMULATED_CPUID)
+                return __do_cpuid_ent_emulated(entry, func, idx, nent, maxnent);
+
+        return __do_cpuid_ent(entry, func, idx, nent, maxnent);
+}
+
 #undef F
 
 struct kvm_cpuid_param {
@@ -529,8 +544,34 @@ static bool is_centaur_cpu(const struct kvm_cpuid_param *param)
         return boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR;
 }
 
-int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
-                                      struct kvm_cpuid_entry2 __user *entries)
+static bool sanity_check_entries(struct kvm_cpuid_entry2 __user *entries,
+                                 __u32 num_entries, unsigned int ioctl_type)
+{
+        int i;
+
+        if (ioctl_type != KVM_GET_EMULATED_CPUID)
+                return false;
+
+        /*
+         * We want to make sure that ->padding is being passed clean from
+         * userspace in case we want to use it for something in the future.
+         *
+         * Sadly, this wasn't enforced for KVM_GET_SUPPORTED_CPUID and so we
+         * have to give ourselves satisfied only with the emulated side. /me
+         * sheds a tear.
+         */
+        for (i = 0; i < num_entries; i++) {
+                if (entries[i].padding[0] ||
+                    entries[i].padding[1] ||
+                    entries[i].padding[2])
+                        return true;
+        }
+        return false;
+}
+
+int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
+                            struct kvm_cpuid_entry2 __user *entries,
+                            unsigned int type)
 {
         struct kvm_cpuid_entry2 *cpuid_entries;
         int limit, nent = 0, r = -E2BIG, i;
@@ -547,6 +588,10 @@ int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
                 goto out;
         if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                 cpuid->nent = KVM_MAX_CPUID_ENTRIES;
+
+        if (sanity_check_entries(entries, cpuid->nent, type))
+                return -EINVAL;
+
         r = -ENOMEM;
         cpuid_entries = vmalloc(sizeof(struct kvm_cpuid_entry2) * cpuid->nent);
         if (!cpuid_entries)
@@ -560,7 +605,7 @@ int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
                         continue;
 
                 r = do_cpuid_ent(&cpuid_entries[nent], ent->func, ent->idx,
-                                &nent, cpuid->nent);
+                                &nent, cpuid->nent, type);
 
                 if (r)
                         goto out_free;
@@ -571,7 +616,7 @@ int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
                 limit = cpuid_entries[nent - 1].eax;
                 for (func = ent->func + 1; func <= limit && nent < cpuid->nent && r == 0; ++func)
                         r = do_cpuid_ent(&cpuid_entries[nent], func, ent->idx,
-                                     &nent, cpuid->nent);
+                                     &nent, cpuid->nent, type);
 
                 if (r)
                         goto out_free;
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index b7fd07984888..f1e4895174b2 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -6,8 +6,9 @@
 void kvm_update_cpuid(struct kvm_vcpu *vcpu);
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
                                               u32 function, u32 index);
-int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
-                                      struct kvm_cpuid_entry2 __user *entries);
+int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
+                            struct kvm_cpuid_entry2 __user *entries,
+                            unsigned int type);
 int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
                              struct kvm_cpuid *cpuid,
                              struct kvm_cpuid_entry __user *entries);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index edf2a07df3a3..3d1e3ee8b39e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2564,6 +2564,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_MMU_SHADOW_CACHE_CONTROL:
         case KVM_CAP_SET_TSS_ADDR:
         case KVM_CAP_EXT_CPUID:
+        case KVM_CAP_EXT_EMUL_CPUID:
         case KVM_CAP_CLOCKSOURCE:
         case KVM_CAP_PIT:
         case KVM_CAP_NOP_IO_DELAY:
@@ -2673,15 +2674,17 @@ long kvm_arch_dev_ioctl(struct file *filp,
                 r = 0;
                 break;
         }
-        case KVM_GET_SUPPORTED_CPUID: {
+        case KVM_GET_SUPPORTED_CPUID:
+        case KVM_GET_EMULATED_CPUID: {
                 struct kvm_cpuid2 __user *cpuid_arg = argp;
                 struct kvm_cpuid2 cpuid;
 
                 r = -EFAULT;
                 if (copy_from_user(&cpuid, cpuid_arg, sizeof cpuid))
                         goto out;
-                r = kvm_dev_ioctl_get_supported_cpuid(&cpuid,
-                                                      cpuid_arg->entries);
+
+                r = kvm_dev_ioctl_get_cpuid(&cpuid, cpuid_arg->entries,
+                                            ioctl);
                 if (r)
                         goto out;
 
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e32e776f20c0..32c60b98ddf8 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -541,6 +541,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_TRACE_ENABLE          __KVM_DEPRECATED_MAIN_W_0x06
 #define KVM_TRACE_PAUSE           __KVM_DEPRECATED_MAIN_0x07
 #define KVM_TRACE_DISABLE         __KVM_DEPRECATED_MAIN_0x08
+#define KVM_GET_EMULATED_CPUID    _IOWR(KVMIO, 0x09, struct kvm_cpuid2)
 
 /*
  * Extension capability list.
@@ -668,6 +669,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_IRQ_XICS 92
 #define KVM_CAP_ARM_EL1_32BIT 93
 #define KVM_CAP_SPAPR_MULTITCE 94
+#define KVM_CAP_EXT_EMUL_CPUID 95
 
 #ifdef KVM_CAP_IRQ_ROUTING