[TSC,trapping,/,migration,2/2] Add TSC KHZ MSR

Commit Message

Zachary Amsden Jan. 6, 2011, 10:10 a.m. UTC

None

Patch

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 7b562b6..723e60d 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -32,6 +32,7 @@ 
 /* Custom MSRs falls in the range 0x4b564d00-0x4b564dff */
 #define MSR_KVM_WALL_CLOCK_NEW  0x4b564d00
 #define MSR_KVM_SYSTEM_TIME_NEW 0x4b564d01
+#define MSR_KVM_TSC_KHZ		0x4b564d02
 
 #define KVM_MAX_MMU_OP_BATCH           32
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bbcd582..ff5addc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -786,10 +786,11 @@  EXPORT_SYMBOL_GPL(kvm_get_dr);
  * kvm-specific. Those are put in the beginning of the list.
  */
 
-#define KVM_SAVE_MSRS_BEGIN	7
+#define KVM_SAVE_MSRS_BEGIN	8
 static u32 msrs_to_save[] = {
 	MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
 	MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
+	MSR_KVM_TSC_KHZ,
 	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
 	HV_X64_MSR_APIC_ASSIST_PAGE,
 	MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
@@ -1608,6 +1609,25 @@  int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		}
 		break;
 	}
+	case MSR_KVM_TSC_KHZ: {
+		struct kvm_arch *arch = &vcpu->kvm->arch;
+		/*
+		 * If userspace indicates a fixed rate TSC, accept attempts
+		 * to set the TSC rate to support incoming migrations.
+		 * This is a write once MSR, to prevent guest tampering.
+		 */
+		if (arch->tsc_flags & KVM_TSC_FLAG_KHZ_MSR_WRITABLE) {
+			if (data > KVM_TSC_MAX_KHZ || data < KVM_TSC_MIN_KHZ)
+				return 1;
+
+			spin_lock(&arch->clock_lock);
+			kvm_arch_set_tsc_khz(vcpu->kvm, data);
+			kvm_setup_tsc_trapping(vcpu);
+			arch->tsc_flags &= ~KVM_TSC_FLAG_KHZ_MSR_WRITABLE;
+			spin_unlock(&arch->clock_lock);
+		}
+		break;
+	}
 	case MSR_IA32_MCG_CTL:
 	case MSR_IA32_MCG_STATUS:
 	case MSR_IA32_MC0_CTL ... MSR_IA32_MC0_CTL + 4 * KVM_MAX_MCE_BANKS - 1:
@@ -1884,6 +1904,9 @@  int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case MSR_KVM_SYSTEM_TIME_NEW:
 		data = vcpu->arch.time;
 		break;
+	case MSR_KVM_TSC_KHZ:
+		data = vcpu->kvm->arch.virtual_tsc_khz;
+		break;
 	case MSR_IA32_P5_MC_ADDR:
 	case MSR_IA32_P5_MC_TYPE:
 	case MSR_IA32_MCG_CAP:
@@ -3615,7 +3638,8 @@  long kvm_arch_vm_ioctl(struct file *filp,
 		r = -EINVAL;
 		if (user_tsc.flags &
 		    ~(KVM_TSC_FLAG_FIXED_RATE |
-		      KVM_TSC_FLAG_SMP_COHERENCY))
+		      KVM_TSC_FLAG_SMP_COHERENCY |
+		      KVM_TSC_FLAG_KHZ_MSR_WRITABLE))
 			goto out;
 
 		if (user_tsc.tsc_khz &&
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index cb97e53..0e316d8 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -628,6 +628,7 @@  struct kvm_tsc_control {
 
 #define KVM_TSC_FLAG_FIXED_RATE		(1 << 0)
 #define KVM_TSC_FLAG_SMP_COHERENCY	(1 << 1)
+#define KVM_TSC_FLAG_KHZ_MSR_WRITABLE	(1 << 2)
 
 #define KVM_TSC_MIN_KHZ 16000		/* 16 MHz, slower than first Pentium */
 #define KVM_TSC_MAX_KHZ 100000000	/* 100 GHz, good for a few years */