KVM: x86: extend "struct x86_emulate_ops" with "get_cpuid"

In order to be able to proceed checks on CPU-specific properties
within the emulator, function "get_cpuid" is introduced.
With "get_cpuid" it is possible to virtually call the guests
"cpuid"-opcode without changing the VM's context.

[mtosatti: cleanup/beautify code]

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

2 files changed, 26 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index ab4092e3214e..c8b28689eeeb 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -190,6 +190,9 @@ struct x86_emulate_ops {
         int (*intercept)(struct x86_emulate_ctxt *ctxt,
                          struct x86_instruction_info *info,
                          enum x86_intercept_stage stage);
+
+        bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt,
+                         u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
 };
 
 typedef u32 __attribute__((vector_size(16))) sse128_t;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 14d6cadc4ba6..8c890e2fa6b6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4180,6 +4180,28 @@ static int emulator_intercept(struct x86_emulate_ctxt *ctxt,
         return kvm_x86_ops->check_intercept(emul_to_vcpu(ctxt), info, stage);
 }
 
+static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
+                               u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+{
+        struct kvm_cpuid_entry2 *cpuid = NULL;
+
+        if (eax && ecx)
+                cpuid = kvm_find_cpuid_entry(emul_to_vcpu(ctxt),
+                                            *eax, *ecx);
+
+        if (cpuid) {
+                *eax = cpuid->eax;
+                *ecx = cpuid->ecx;
+                if (ebx)
+                        *ebx = cpuid->ebx;
+                if (edx)
+                        *edx = cpuid->edx;
+                return true;
+        }
+
+        return false;
+}
+
 static struct x86_emulate_ops emulate_ops = {
         .read_std            = kvm_read_guest_virt_system,
         .write_std           = kvm_write_guest_virt_system,
@@ -4211,6 +4233,7 @@ static struct x86_emulate_ops emulate_ops = {
         .get_fpu             = emulator_get_fpu,
         .put_fpu             = emulator_put_fpu,
         .intercept           = emulator_intercept,
+        .get_cpuid           = emulator_get_cpuid,
 };
 
 static void cache_all_regs(struct kvm_vcpu *vcpu)