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Commit 92a1f12d authored by Joerg Roedel's avatar Joerg Roedel Committed by Avi Kivity
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KVM: X86: Implement userspace interface to set virtual_tsc_khz 



This patch implements two new vm-ioctls to get and set the
virtual_tsc_khz if the machine supports tsc-scaling. Setting
the tsc-frequency is only possible before userspace creates
any vcpu.

Signed-off-by: default avatarJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 857e4099

Documentation/kvm/api.txt

+23 −0
Original line number Diff line number Diff line
@@ -1263,6 +1263,29 @@ struct kvm_assigned_msix_entry { 
	__u16 padding[3];

};



4.54 KVM_SET_TSC_KHZ



Capability: KVM_CAP_TSC_CONTROL

Architectures: x86

Type: vcpu ioctl

Parameters: virtual tsc_khz

Returns: 0 on success, -1 on error



Specifies the tsc frequency for the virtual machine. The unit of the

frequency is KHz.



4.55 KVM_GET_TSC_KHZ



Capability: KVM_CAP_GET_TSC_KHZ

Architectures: x86

Type: vcpu ioctl

Parameters: none

Returns: virtual tsc-khz on success, negative value on error



Returns the tsc frequency of the guest. The unit of the return value is

KHz. If the host has unstable tsc this ioctl returns -EIO instead as an

error.



5. The kvm_run structure



Application code obtains a pointer to the kvm_run structure by

arch/x86/include/asm/kvm_host.h

+7 −0
Original line number Diff line number Diff line
@@ -655,6 +655,13 @@ u8 kvm_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn); 


extern bool tdp_enabled;



/* control of guest tsc rate supported? */

extern bool kvm_has_tsc_control;

/* minimum supported tsc_khz for guests */

extern u32  kvm_min_guest_tsc_khz;

/* maximum supported tsc_khz for guests */

extern u32  kvm_max_guest_tsc_khz;



enum emulation_result {

	EMULATE_DONE,       /* no further processing */

	EMULATE_DO_MMIO,      /* kvm_run filled with mmio request */

arch/x86/kvm/svm.c

+20 −0
Original line number Diff line number Diff line
@@ -64,6 +64,8 @@ MODULE_LICENSE("GPL"); 
#define DEBUGCTL_RESERVED_BITS (~(0x3fULL))



#define TSC_RATIO_RSVD          0xffffff0000000000ULL

#define TSC_RATIO_MIN		0x0000000000000001ULL

#define TSC_RATIO_MAX		0x000000ffffffffffULL



static bool erratum_383_found __read_mostly;
@@ -189,6 +191,7 @@ static int nested_svm_intercept(struct vcpu_svm *svm); 
static int nested_svm_vmexit(struct vcpu_svm *svm);

static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,

				      bool has_error_code, u32 error_code);

static u64 __scale_tsc(u64 ratio, u64 tsc);



enum {

	VMCB_INTERCEPTS, /* Intercept vectors, TSC offset,
@@ -798,6 +801,23 @@ static __init int svm_hardware_setup(void) 
	if (boot_cpu_has(X86_FEATURE_FXSR_OPT))

		kvm_enable_efer_bits(EFER_FFXSR);



	if (boot_cpu_has(X86_FEATURE_TSCRATEMSR)) {

		u64 max;



		kvm_has_tsc_control = true;



		/*

		 * Make sure the user can only configure tsc_khz values that

		 * fit into a signed integer.

		 * A min value is not calculated needed because it will always

		 * be 1 on all machines and a value of 0 is used to disable

		 * tsc-scaling for the vcpu.

		 */

		max = min(0x7fffffffULL, __scale_tsc(tsc_khz, TSC_RATIO_MAX));



		kvm_max_guest_tsc_khz = max;

	}



	if (nested) {

		printk(KERN_INFO "kvm: Nested Virtualization enabled\n");

		kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE);

arch/x86/kvm/x86.c

+35 −0
Original line number Diff line number Diff line
@@ -87,6 +87,11 @@ EXPORT_SYMBOL_GPL(kvm_x86_ops); 
int ignore_msrs = 0;

module_param_named(ignore_msrs, ignore_msrs, bool, S_IRUGO | S_IWUSR);



bool kvm_has_tsc_control;

EXPORT_SYMBOL_GPL(kvm_has_tsc_control);

u32  kvm_max_guest_tsc_khz;

EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz);



#define KVM_NR_SHARED_MSRS 16



struct kvm_shared_msrs_global {
@@ -1986,6 +1991,7 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_X86_ROBUST_SINGLESTEP:

	case KVM_CAP_XSAVE:

	case KVM_CAP_ASYNC_PF:

	case KVM_CAP_GET_TSC_KHZ:

		r = 1;

		break;

	case KVM_CAP_COALESCED_MMIO:
@@ -2012,6 +2018,9 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_XCRS:

		r = cpu_has_xsave;

		break;

	case KVM_CAP_TSC_CONTROL:

		r = kvm_has_tsc_control;

		break;

	default:

		r = 0;

		break;
@@ -3045,6 +3054,32 @@ long kvm_arch_vcpu_ioctl(struct file *filp, 
		r = kvm_vcpu_ioctl_x86_set_xcrs(vcpu, u.xcrs);

		break;

	}

	case KVM_SET_TSC_KHZ: {

		u32 user_tsc_khz;



		r = -EINVAL;

		if (!kvm_has_tsc_control)

			break;



		user_tsc_khz = (u32)arg;



		if (user_tsc_khz >= kvm_max_guest_tsc_khz)

			goto out;



		kvm_x86_ops->set_tsc_khz(vcpu, user_tsc_khz);



		r = 0;

		goto out;

	}

	case KVM_GET_TSC_KHZ: {

		r = -EIO;

		if (check_tsc_unstable())

			goto out;



		r = vcpu_tsc_khz(vcpu);



		goto out;

	}

	default:

		r = -EINVAL;

	}

include/linux/kvm.h

+5 −0
Original line number Diff line number Diff line
@@ -541,6 +541,8 @@ struct kvm_ppc_pvinfo { 
#define KVM_CAP_PPC_GET_PVINFO 57

#define KVM_CAP_PPC_IRQ_LEVEL 58

#define KVM_CAP_ASYNC_PF 59

#define KVM_CAP_TSC_CONTROL 60

#define KVM_CAP_GET_TSC_KHZ 61



#ifdef KVM_CAP_IRQ_ROUTING
@@ -677,6 +679,9 @@ struct kvm_clock_data { 
#define KVM_SET_PIT2              _IOW(KVMIO,  0xa0, struct kvm_pit_state2)

/* Available with KVM_CAP_PPC_GET_PVINFO */

#define KVM_PPC_GET_PVINFO	  _IOW(KVMIO,  0xa1, struct kvm_ppc_pvinfo)

/* Available with KVM_CAP_TSC_CONTROL */

#define KVM_SET_TSC_KHZ           _IO(KVMIO,  0xa2)

#define KVM_GET_TSC_KHZ           _IO(KVMIO,  0xa3)



/*

 * ioctls for vcpu fds