This is a note to let you know that I've just added the patch titled
KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: kvm-async_pf-fix-df-due-to-inject-page-not-present-and-page-ready-exceptions-simultaneously.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@vger.kernel.org know about it.
From 9a6e7c39810e4a8bc7fc95056cefb40583fe07ef Mon Sep 17 00:00:00 2001
From: Wanpeng Li wanpeng.li@hotmail.com Date: Thu, 14 Sep 2017 03:54:16 -0700 Subject: KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
From: Wanpeng Li wanpeng.li@hotmail.com
commit 9a6e7c39810e4a8bc7fc95056cefb40583fe07ef upstream.
qemu-system-x86-8600 [004] d..1 7205.687530: kvm_entry: vcpu 2 qemu-system-x86-8600 [004] .... 7205.687532: kvm_exit: reason EXCEPTION_NMI rip 0xffffffffa921297d info ffffeb2c0e44e018 80000b0e qemu-system-x86-8600 [004] .... 7205.687532: kvm_page_fault: address ffffeb2c0e44e018 error_code 0 qemu-system-x86-8600 [004] .... 7205.687620: kvm_try_async_get_page: gva = 0xffffeb2c0e44e018, gfn = 0x427e4e qemu-system-x86-8600 [004] .N.. 7205.687628: kvm_async_pf_not_present: token 0x8b002 gva 0xffffeb2c0e44e018 kworker/4:2-7814 [004] .... 7205.687655: kvm_async_pf_completed: gva 0xffffeb2c0e44e018 address 0x7fcc30c4e000 qemu-system-x86-8600 [004] .... 7205.687703: kvm_async_pf_ready: token 0x8b002 gva 0xffffeb2c0e44e018 qemu-system-x86-8600 [004] d..1 7205.687711: kvm_entry: vcpu 2
After running some memory intensive workload in guest, I catch the kworker which completes the GUP too quickly, and queues an "Page Ready" #PF exception after the "Page not Present" exception before the next vmentry as the above trace which will result in #DF injected to guest.
This patch fixes it by clearing the queue for "Page not Present" if "Page Ready" occurs before the next vmentry since the GUP has already got the required page and shadow page table has already been fixed by "Page Ready" handler.
Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Signed-off-by: Wanpeng Li wanpeng.li@hotmail.com Fixes: 7c90705bf2a3 ("KVM: Inject asynchronous page fault into a PV guest if page is swapped out.") [Changed indentation and added clearing of injected. - Radim] Signed-off-by: Radim Krčmář rkrcmar@redhat.com [port from upstream v4.14-rc1, Don't assign to kvm_queued_exception::injected or x86_exception::async_page_fault] Signed-off-by: Jack Wang jinpu.wang@profitbricks.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/x86.c | 34 ++++++++++++++++++++++++++-------- 1 file changed, 26 insertions(+), 8 deletions(-)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8427,6 +8427,13 @@ static int apf_put_user(struct kvm_vcpu sizeof(val)); }
+static int apf_get_user(struct kvm_vcpu *vcpu, u32 *val) +{ + + return kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.apf.data, val, + sizeof(u32)); +} + void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu, struct kvm_async_pf *work) { @@ -8453,6 +8460,7 @@ void kvm_arch_async_page_present(struct struct kvm_async_pf *work) { struct x86_exception fault; + u32 val;
if (work->wakeup_all) work->arch.token = ~0; /* broadcast wakeup */ @@ -8460,14 +8468,24 @@ void kvm_arch_async_page_present(struct kvm_del_async_pf_gfn(vcpu, work->arch.gfn); trace_kvm_async_pf_ready(work->arch.token, work->gva);
- if ((vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED) && - !apf_put_user(vcpu, KVM_PV_REASON_PAGE_READY)) { - fault.vector = PF_VECTOR; - fault.error_code_valid = true; - fault.error_code = 0; - fault.nested_page_fault = false; - fault.address = work->arch.token; - kvm_inject_page_fault(vcpu, &fault); + if (vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED && + !apf_get_user(vcpu, &val)) { + if (val == KVM_PV_REASON_PAGE_NOT_PRESENT && + vcpu->arch.exception.pending && + vcpu->arch.exception.nr == PF_VECTOR && + !apf_put_user(vcpu, 0)) { + vcpu->arch.exception.pending = false; + vcpu->arch.exception.nr = 0; + vcpu->arch.exception.has_error_code = false; + vcpu->arch.exception.error_code = 0; + } else if (!apf_put_user(vcpu, KVM_PV_REASON_PAGE_READY)) { + fault.vector = PF_VECTOR; + fault.error_code_valid = true; + fault.error_code = 0; + fault.nested_page_fault = false; + fault.address = work->arch.token; + kvm_inject_page_fault(vcpu, &fault); + } } vcpu->arch.apf.halted = false; vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
Patches currently in stable-queue which might be from wanpeng.li@hotmail.com are
queue-4.9/kvm-x86-fix-escape-of-guest-dr6-to-the-host.patch queue-4.9/kvm-async_pf-fix-df-due-to-inject-page-not-present-and-page-ready-exceptions-simultaneously.patch