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Commit 344d9588 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
Browse files

KVM: Add PV MSR to enable asynchronous page faults delivery. 



Guest enables async PF vcpu functionality using this MSR.

Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent ca3f1017

Documentation/kvm/cpuid.txt

+3 −0
Original line number Diff line number Diff line
@@ -36,6 +36,9 @@ KVM_FEATURE_MMU_OP || 2 || deprecated. 
KVM_FEATURE_CLOCKSOURCE2           ||     3 || kvmclock available at msrs

                                   ||       || 0x4b564d00 and 0x4b564d01

------------------------------------------------------------------------------

KVM_FEATURE_ASYNC_PF               ||     4 || async pf can be enabled by

                                   ||       || writing to msr 0x4b564d02

------------------------------------------------------------------------------

KVM_FEATURE_CLOCKSOURCE_STABLE_BIT ||    24 || host will warn if no guest-side

                                   ||       || per-cpu warps are expected in

                                   ||       || kvmclock.

Documentation/kvm/msr.txt

+34 −1
Original line number Diff line number Diff line
@@ -3,7 +3,6 @@ Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010 
=====================================================



KVM makes use of some custom MSRs to service some requests.

At present, this facility is only used by kvmclock.



Custom MSRs have a range reserved for them, that goes from

0x4b564d00 to 0x4b564dff. There are MSRs outside this area,
@@ -151,3 +150,37 @@ MSR_KVM_SYSTEM_TIME: 0x12 
			return PRESENT;

		} else

			return NON_PRESENT;



MSR_KVM_ASYNC_PF_EN: 0x4b564d02

	data: Bits 63-6 hold 64-byte aligned physical address of a

	64 byte memory area which must be in guest RAM and must be

	zeroed. Bits 5-1 are reserved and should be zero. Bit 0 is 1

	when asynchronous page faults are enabled on the vcpu 0 when

	disabled.



	First 4 byte of 64 byte memory location will be written to by

	the hypervisor at the time of asynchronous page fault (APF)

	injection to indicate type of asynchronous page fault. Value

	of 1 means that the page referred to by the page fault is not

	present. Value 2 means that the page is now available. Disabling

	interrupt inhibits APFs. Guest must not enable interrupt

	before the reason is read, or it may be overwritten by another

	APF. Since APF uses the same exception vector as regular page

	fault guest must reset the reason to 0 before it does

	something that can generate normal page fault.  If during page

	fault APF reason is 0 it means that this is regular page

	fault.



	During delivery of type 1 APF cr2 contains a token that will

	be used to notify a guest when missing page becomes

	available. When page becomes available type 2 APF is sent with

	cr2 set to the token associated with the page. There is special

	kind of token 0xffffffff which tells vcpu that it should wake

	up all processes waiting for APFs and no individual type 2 APFs

	will be sent.



	If APF is disabled while there are outstanding APFs, they will

	not be delivered.



	Currently type 2 APF will be always delivered on the same vcpu as

	type 1 was, but guest should not rely on that.

arch/x86/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -419,6 +419,8 @@ struct kvm_vcpu_arch { 
	struct {

		bool halted;

		gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)];

		struct gfn_to_hva_cache data;

		u64 msr_val;

	} apf;

};

arch/x86/include/asm/kvm_para.h

+4 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
 * are available. The use of 0x11 and 0x12 is deprecated

 */

#define KVM_FEATURE_CLOCKSOURCE2        3

#define KVM_FEATURE_ASYNC_PF		4



/* The last 8 bits are used to indicate how to interpret the flags field

 * in pvclock structure. If no bits are set, all flags are ignored.
@@ -32,9 +33,12 @@ 
/* 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_ASYNC_PF_EN 0x4b564d02



#define KVM_MAX_MMU_OP_BATCH           32



#define KVM_ASYNC_PF_ENABLED			(1 << 0)



/* Operations for KVM_HC_MMU_OP */

#define KVM_MMU_OP_WRITE_PTE            1

#define KVM_MMU_OP_FLUSH_TLB	        2

arch/x86/kvm/x86.c

+36 −2
Original line number Diff line number Diff line
@@ -783,12 +783,12 @@ 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,

	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,

	HV_X64_MSR_APIC_ASSIST_PAGE,

	HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN,

	MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,

	MSR_STAR,

#ifdef CONFIG_X86_64
@@ -1425,6 +1425,29 @@ static int set_msr_hyperv(struct kvm_vcpu *vcpu, u32 msr, u64 data) 
	return 0;

}



static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)

{

	gpa_t gpa = data & ~0x3f;



	/* Bits 1:5 are resrved, Should be zero */

	if (data & 0x3e)

		return 1;



	vcpu->arch.apf.msr_val = data;



	if (!(data & KVM_ASYNC_PF_ENABLED)) {

		kvm_clear_async_pf_completion_queue(vcpu);

		kvm_async_pf_hash_reset(vcpu);

		return 0;

	}



	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa))

		return 1;



	kvm_async_pf_wakeup_all(vcpu);

	return 0;

}



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

{

	switch (msr) {
@@ -1506,6 +1529,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) 
		}

		break;

	}

	case MSR_KVM_ASYNC_PF_EN:

		if (kvm_pv_enable_async_pf(vcpu, data))

			return 1;

		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:
@@ -1782,6 +1809,9 @@ 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_ASYNC_PF_EN:

		data = vcpu->arch.apf.msr_val;

		break;

	case MSR_IA32_P5_MC_ADDR:

	case MSR_IA32_P5_MC_TYPE:

	case MSR_IA32_MCG_CAP:
@@ -1929,6 +1959,7 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_DEBUGREGS:

	case KVM_CAP_X86_ROBUST_SINGLESTEP:

	case KVM_CAP_XSAVE:

	case KVM_CAP_ASYNC_PF:

		r = 1;

		break;

	case KVM_CAP_COALESCED_MMIO:
@@ -5792,6 +5823,8 @@ free_vcpu: 


void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)

{

	vcpu->arch.apf.msr_val = 0;



	vcpu_load(vcpu);

	kvm_mmu_unload(vcpu);

	vcpu_put(vcpu);
@@ -5811,6 +5844,7 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu) 
	vcpu->arch.dr7 = DR7_FIXED_1;



	kvm_make_request(KVM_REQ_EVENT, vcpu);

	vcpu->arch.apf.msr_val = 0;



	kvm_clear_async_pf_completion_queue(vcpu);

	kvm_async_pf_hash_reset(vcpu);