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

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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: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Gleb Natapov 2010-10-14 11:22:55 +02:00 • committed by Avi Kivity
commit 6adba52742
5 changed files with 11 additions and 4 deletions
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5
Documentation/kvm/msr.txt
View file

@ -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)

1
arch/x86/include/asm/kvm_host.h
View file

@ -422,6 +422,7 @@ struct kvm_vcpu_arch {
struct gfn_to_hva_cache data;
u64 msr_val;
u32 id;
bool send_user_only;
} apf;
};

1
arch/x86/include/asm/kvm_para.h
View file

@ -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

3
arch/x86/kernel/kvm.c
View file

@ -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",

5
arch/x86/kvm/x86.c
View file

@ -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;
}