This is a note to let you know that I've just added the patch titled KVM: async_pf: avoid async pf injection when in guest mode to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-async_pf-avoid-async-pf-injection-when-in-guest-mode.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 9bc1f09f6fa76fdf31eb7d6a4a4df43574725f93 Mon Sep 17 00:00:00 2001 From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> Date: Thu, 8 Jun 2017 20:13:40 -0700 Subject: KVM: async_pf: avoid async pf injection when in guest mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> commit 9bc1f09f6fa76fdf31eb7d6a4a4df43574725f93 upstream. 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: __schedule+0x3cd/0xb30 schedule+0x40/0x90 kvm_async_pf_task_wait+0x1cc/0x270 ? __vfs_read+0x37/0x150 ? prepare_to_swait+0x22/0x70 do_async_page_fault+0x77/0xb0 ? do_async_page_fault+0x77/0xb0 async_page_fault+0x28/0x30 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 <pbonzini@xxxxxxxxxx> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/mmu.c | 7 +++++-- arch/x86/kvm/mmu.h | 1 + arch/x86/kvm/x86.c | 3 +-- 3 files changed, 7 insertions(+), 4 deletions(-) --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3489,12 +3489,15 @@ static int kvm_arch_setup_async_pf(struc 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) || kvm_event_needs_reinjection(vcpu))) return false; + if (is_guest_mode(vcpu)) + return false; + return kvm_x86_ops->interrupt_allowed(vcpu); } @@ -3510,7 +3513,7 @@ static bool try_async_pf(struct kvm_vcpu 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); --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -75,6 +75,7 @@ enum { 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 kvm_can_do_async_pf(struct kvm_vcpu *vcpu); static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm) { --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8444,8 +8444,7 @@ bool kvm_arch_can_inject_async_page_pres if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED)) return true; else - return !kvm_event_needs_reinjection(vcpu) && - kvm_x86_ops->interrupt_allowed(vcpu); + return kvm_can_do_async_pf(vcpu); } void kvm_arch_start_assignment(struct kvm *kvm) Patches currently in stable-queue which might be from wanpeng.li@xxxxxxxxxxx are queue-4.9/kvm-async_pf-fix-rcu_irq_enter-with-irqs-enabled.patch queue-4.9/kvm-async_pf-avoid-async-pf-injection-when-in-guest-mode.patch queue-4.9/kvm-cpuid-fix-read-write-out-of-bounds-vulnerability-in-cpuid-emulation.patch