Commit 18068523 authored by Glauber de Oliveira Costa's avatar Glauber de Oliveira Costa Committed by Avi Kivity
Browse files

KVM: paravirtualized clocksource: host part 



This is the host part of kvm clocksource implementation. As it does
not include clockevents, it is a fairly simple implementation. We
only have to register a per-vcpu area, and start writing to it periodically.

The area is binary compatible with xen, as we use the same shadow_info
structure.

[marcelo: fix bad_page on MSR_KVM_SYSTEM_TIME]
[avi: save full value of the msr, even if enable bit is clear]
[avi: clear previous value of time_page]

Signed-off-by: default avatarGlauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 24e09cbf

arch/x86/kvm/x86.c

+112 −1
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include "irq.h"

#include "mmu.h"



#include <linux/clocksource.h>

#include <linux/kvm.h>

#include <linux/fs.h>

#include <linux/vmalloc.h>
@@ -424,7 +425,7 @@ static u32 msrs_to_save[] = { 
#ifdef CONFIG_X86_64

	MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,

#endif

	MSR_IA32_TIME_STAMP_COUNTER,

	MSR_IA32_TIME_STAMP_COUNTER, MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,

};



static unsigned num_msrs_to_save;
@@ -482,6 +483,70 @@ static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data) 
	return kvm_set_msr(vcpu, index, *data);

}



static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)

{

	static int version;

	struct kvm_wall_clock wc;

	struct timespec wc_ts;



	if (!wall_clock)

		return;



	version++;



	down_read(&kvm->slots_lock);

	kvm_write_guest(kvm, wall_clock, &version, sizeof(version));



	wc_ts = current_kernel_time();

	wc.wc_sec = wc_ts.tv_sec;

	wc.wc_nsec = wc_ts.tv_nsec;

	wc.wc_version = version;



	kvm_write_guest(kvm, wall_clock, &wc, sizeof(wc));



	version++;

	kvm_write_guest(kvm, wall_clock, &version, sizeof(version));

	up_read(&kvm->slots_lock);

}



static void kvm_write_guest_time(struct kvm_vcpu *v)

{

	struct timespec ts;

	unsigned long flags;

	struct kvm_vcpu_arch *vcpu = &v->arch;

	void *shared_kaddr;



	if ((!vcpu->time_page))

		return;



	/* Keep irq disabled to prevent changes to the clock */

	local_irq_save(flags);

	kvm_get_msr(v, MSR_IA32_TIME_STAMP_COUNTER,

			  &vcpu->hv_clock.tsc_timestamp);

	ktime_get_ts(&ts);

	local_irq_restore(flags);



	/* With all the info we got, fill in the values */



	vcpu->hv_clock.system_time = ts.tv_nsec +

				     (NSEC_PER_SEC * (u64)ts.tv_sec);

	/*

	 * The interface expects us to write an even number signaling that the

	 * update is finished. Since the guest won't see the intermediate

	 * state, we just write "2" at the end

	 */

	vcpu->hv_clock.version = 2;



	shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);



	memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,

		sizeof(vcpu->hv_clock));



	kunmap_atomic(shared_kaddr, KM_USER0);



	mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);

}





int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)

{
@@ -511,6 +576,44 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) 
	case MSR_IA32_MISC_ENABLE:

		vcpu->arch.ia32_misc_enable_msr = data;

		break;

	case MSR_KVM_WALL_CLOCK:

		vcpu->kvm->arch.wall_clock = data;

		kvm_write_wall_clock(vcpu->kvm, data);

		break;

	case MSR_KVM_SYSTEM_TIME: {

		if (vcpu->arch.time_page) {

			kvm_release_page_dirty(vcpu->arch.time_page);

			vcpu->arch.time_page = NULL;

		}



		vcpu->arch.time = data;



		/* we verify if the enable bit is set... */

		if (!(data & 1))

			break;



		/* ...but clean it before doing the actual write */

		vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);



		vcpu->arch.hv_clock.tsc_to_system_mul =

					clocksource_khz2mult(tsc_khz, 22);

		vcpu->arch.hv_clock.tsc_shift = 22;



		down_read(&current->mm->mmap_sem);

		down_read(&vcpu->kvm->slots_lock);

		vcpu->arch.time_page =

				gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT);

		up_read(&vcpu->kvm->slots_lock);

		up_read(&current->mm->mmap_sem);



		if (is_error_page(vcpu->arch.time_page)) {

			kvm_release_page_clean(vcpu->arch.time_page);

			vcpu->arch.time_page = NULL;

		}



		kvm_write_guest_time(vcpu);

		break;

	}

	default:

		pr_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n", msr, data);

		return 1;
@@ -569,6 +672,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata) 
	case MSR_EFER:

		data = vcpu->arch.shadow_efer;

		break;

	case MSR_KVM_WALL_CLOCK:

		data = vcpu->kvm->arch.wall_clock;

		break;

	case MSR_KVM_SYSTEM_TIME:

		data = vcpu->arch.time;

		break;

	default:

		pr_unimpl(vcpu, "unhandled rdmsr: 0x%x\n", msr);

		return 1;
@@ -696,6 +805,7 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_USER_MEMORY:

	case KVM_CAP_SET_TSS_ADDR:

	case KVM_CAP_EXT_CPUID:

	case KVM_CAP_CLOCKSOURCE:

		r = 1;

		break;

	case KVM_CAP_VAPIC:
@@ -771,6 +881,7 @@ out: 
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

{

	kvm_x86_ops->vcpu_load(vcpu, cpu);

	kvm_write_guest_time(vcpu);

}



void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)

include/asm-x86/kvm_host.h

+7 −0
Original line number Diff line number Diff line
@@ -262,6 +262,11 @@ struct kvm_vcpu_arch { 
	/* emulate context */



	struct x86_emulate_ctxt emulate_ctxt;



	gpa_t time;

	struct kvm_vcpu_time_info hv_clock;

	unsigned int time_offset;

	struct page *time_page;

};



struct kvm_mem_alias {
@@ -288,6 +293,8 @@ struct kvm_arch{ 
	int round_robin_prev_vcpu;

	unsigned int tss_addr;

	struct page *apic_access_page;



	gpa_t wall_clock;

};



struct kvm_vm_stat {

include/asm-x86/kvm_para.h

+25 −0
Original line number Diff line number Diff line
@@ -10,10 +10,35 @@ 
 * paravirtualization, the appropriate feature bit should be checked.

 */

#define KVM_CPUID_FEATURES	0x40000001

#define KVM_FEATURE_CLOCKSOURCE 0



#define MSR_KVM_WALL_CLOCK  0x11

#define MSR_KVM_SYSTEM_TIME 0x12



#ifdef __KERNEL__

#include <asm/processor.h>



/* xen binary-compatible interface. See xen headers for details */

struct kvm_vcpu_time_info {

	uint32_t version;

	uint32_t pad0;

	uint64_t tsc_timestamp;

	uint64_t system_time;

	uint32_t tsc_to_system_mul;

	int8_t   tsc_shift;

	int8_t	 pad[3];

} __attribute__((__packed__)); /* 32 bytes */



struct kvm_wall_clock {

	uint32_t wc_version;

	uint32_t wc_sec;

	uint32_t wc_nsec;

} __attribute__((__packed__));





extern void kvmclock_init(void);





/* This instruction is vmcall.  On non-VT architectures, it will generate a

 * trap that we will then rewrite to the appropriate instruction.

 */

include/linux/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -233,6 +233,7 @@ struct kvm_vapic_addr { 
#define KVM_CAP_SET_TSS_ADDR 4

#define KVM_CAP_VAPIC 6

#define KVM_CAP_EXT_CPUID 7

#define KVM_CAP_CLOCKSOURCE 8



/*

 * ioctls for VM fds

CRA Git | Maintained and supported by SUSTech CRA and CCSE