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Commit 6adba527 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
Browse files

KVM: Let host know whether the guest can handle async PF in non-userspace context. 



If guest can detect that it runs in non-preemptable context it can
handle async PFs at any time, so let host know that it can send async
PF even if guest cpu is not in userspace.

Acked-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 6c047cd9

Documentation/kvm/msr.txt

+3 −2
Original line number Diff line number Diff line
@@ -154,9 +154,10 @@ MSR_KVM_SYSTEM_TIME: 0x12 
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

	zeroed. Bits 5-2 are reserved and should be zero. Bit 0 is 1

	when asynchronous page faults are enabled on the vcpu 0 when

	disabled.

	disabled. Bit 2 is 1 if asynchronous page faults can be injected

	when vcpu is in cpl == 0.



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

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

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -422,6 +422,7 @@ struct kvm_vcpu_arch { 
		struct gfn_to_hva_cache data;

		u64 msr_val;

		u32 id;

		bool send_user_only;

	} apf;

};

arch/x86/include/asm/kvm_para.h

+1 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#define KVM_MAX_MMU_OP_BATCH           32



#define KVM_ASYNC_PF_ENABLED			(1 << 0)

#define KVM_ASYNC_PF_SEND_ALWAYS		(1 << 1)



/* Operations for KVM_HC_MMU_OP */

#define KVM_MMU_OP_WRITE_PTE            1

arch/x86/kernel/kvm.c

+3 −0
Original line number Diff line number Diff line
@@ -449,6 +449,9 @@ void __cpuinit kvm_guest_cpu_init(void) 
	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {

		u64 pa = __pa(&__get_cpu_var(apf_reason));



#ifdef CONFIG_PREEMPT

		pa |= KVM_ASYNC_PF_SEND_ALWAYS;

#endif

		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);

		__get_cpu_var(apf_reason).enabled = 1;

		printk(KERN_INFO"KVM setup async PF for cpu %d\n",

arch/x86/kvm/x86.c

+3 −2
Original line number Diff line number Diff line
@@ -1429,8 +1429,8 @@ 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)

	/* Bits 2:5 are resrved, Should be zero */

	if (data & 0x3c)

		return 1;



	vcpu->arch.apf.msr_val = data;
@@ -1444,6 +1444,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data) 
	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa))

		return 1;



	vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);

	kvm_async_pf_wakeup_all(vcpu);

	return 0;

}