Commit 9bc1f09f authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini

KVM: async_pf: avoid async pf injection when in guest mode

 INFO: task gnome-terminal-:1734 blocked for more than 120 seconds.
       Not tainted 4.12.0-rc4+ #8
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 gnome-terminal- D    0  1734   1015 0x00000000
 Call Trace:
  ? __vfs_read+0x37/0x150
  ? prepare_to_swait+0x22/0x70
  ? do_async_page_fault+0x77/0xb0

This is triggered by running both win7 and win2016 on L1 KVM simultaneously,
and then gives stress to memory on L1, I can observed this hang on L1 when
at least ~70% swap area is occupied on L0.

This is due to async pf was injected to L2 which should be injected to L1,
L2 guest starts receiving pagefault w/ bogus %cr2(apf token from the host
actually), and L1 guest starts accumulating tasks stuck in D state in
kvm_async_pf_task_wait() since missing PAGE_READY async_pfs.

This patch fixes the hang by doing async pf when executing L1 guest.

Cc: Paolo Bonzini <>
Cc: Radim Krčmář <>
Signed-off-by: default avatarWanpeng Li <>
Signed-off-by: default avatarPaolo Bonzini <>
parent 9e53932d
......@@ -3698,12 +3698,15 @@ static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn)
return kvm_setup_async_pf(vcpu, gva, kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
static bool can_do_async_pf(struct kvm_vcpu *vcpu)
bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu)
if (unlikely(!lapic_in_kernel(vcpu) ||
return false;
if (is_guest_mode(vcpu))
return false;
return kvm_x86_ops->interrupt_allowed(vcpu);
......@@ -3719,7 +3722,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
if (!async)
return false; /* *pfn has correct page already */
if (!prefault && can_do_async_pf(vcpu)) {
if (!prefault && kvm_can_do_async_pf(vcpu)) {
trace_kvm_try_async_get_page(gva, gfn);
if (kvm_find_async_pf_gfn(vcpu, gfn)) {
trace_kvm_async_pf_doublefault(gva, gfn);
......@@ -76,6 +76,7 @@ int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct);
void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu);
void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
bool accessed_dirty);
bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu);
static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm)
......@@ -8607,8 +8607,7 @@ bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu)
if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED))
return true;
return !kvm_event_needs_reinjection(vcpu) &&
return kvm_can_do_async_pf(vcpu);
void kvm_arch_start_assignment(struct kvm *kvm)
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