From: Sean Christopherson <seanjc@google.com>
To: lkp@lists.01.org
Subject: Re: [KVM] 7055fb1131: WARNING:at_arch/x86/kvm/x86.c:#inject_pending_event[kvm]
Date: Fri, 30 Sep 2022 13:35:01 +0000 [thread overview]
Message-ID: <YzbwhXJnQQPpFm7Q@google.com> (raw)
In-Reply-To: <202209301338.aca913c3-yujie.liu@intel.com>
[-- Attachment #1: Type: text/plain, Size: 2553 bytes --]
On Fri, Sep 30, 2022, kernel test robot wrote:
> Greeting,
>
> FYI, we noticed the following commit (built with gcc-11):
>
> commit: 7055fb11311622852c16463b1ccaa59e7691e42e ("KVM: x86: Treat pending TRIPLE_FAULT requests as pending exceptions")
> https://git.kernel.org/cgit/virt/kvm/kvm.git queue
...
> # ==== Test Assertion Failure ====
> # x86_64/mmio_warning_test.c:117: warnings_before == warnings_after
...
> [ 100.924976][ T4704] ------------[ cut here ]------------
> [ 100.931287][ T4704] WARNING: CPU: 67 PID: 4704 at arch/x86/kvm/x86.c:9934 inject_pending_event+0x6e6/0xe00 [kvm]
> [ 101.237320][ T4704] Call Trace:
> [ 101.241522][ T4704] <TASK>
> [ 101.245343][ T4704] vcpu_enter_guest+0x61a/0x3540 [kvm]
> [ 101.271009][ T4704] vcpu_run+0xbe/0x780 [kvm]
> [ 101.282791][ T4704] kvm_arch_vcpu_ioctl_run+0x334/0x1540 [kvm]
> [ 101.289810][ T4704] kvm_vcpu_ioctl+0x455/0xb00 [kvm]
> [ 101.359680][ T4704] __x64_sys_ioctl+0x128/0x1c0
> [ 101.365052][ T4704] do_syscall_64+0x38/0xc0
> [ 101.370066][ T4704] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [ 101.376647][ T4704] RIP: 0033:0x7f2a78126547
Good ol' emulated real mode. The warning exists to assert that KVM didn't queue
a new exception while injecting events, but when emulating Real Mode due to lack
of unrestricted guest, KVM needs to emulate the actual event injection and so can
trigger triple fault.
Ideally the assertion would filter out this exact case, but rmode.vm86_active is
buried in vcpu_vmx. Easiest thing is to just exempt KVM_REQ_TRIPLE_FAULT.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eb9d2c23fb04..1d02cc416cbc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9972,7 +9972,15 @@ static int kvm_check_and_inject_events(struct kvm_vcpu *vcpu,
kvm_x86_ops.nested_ops->has_events(vcpu))
*req_immediate_exit = true;
- WARN_ON(kvm_is_exception_pending(vcpu));
+ /*
+ * KVM should never attempt to queue a new exception while injecting an
+ * event, at this point KVM is done emulating and should only propagate
+ * the exception to the VMCS/VMCB. Exempt triple faults as VMX without
+ * unrestricted guest needs to emulate Real Mode events and queues a
+ * triple fault if injection fails (see kvm_inject_realmode_interrupt()).
+ */
+ WARN_ON_ONCE(vcpu->arch.exception.pending ||
+ vcpu->arch.exception_vmexit.pending);
return 0;
out:
WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: kernel test robot <yujie.liu@intel.com>
Cc: lkp@lists.01.org, lkp@intel.com,
Paolo Bonzini <pbonzini@redhat.com>,
Maxim Levitsky <mlevitsk@redhat.com>,
kvm@vger.kernel.org, Robert Hu <robert.hu@intel.com>,
Farrah Chen <farrah.chen@intel.com>,
Danmei Wei <danmei.wei@intel.com>
Subject: Re: [KVM] 7055fb1131: WARNING:at_arch/x86/kvm/x86.c:#inject_pending_event[kvm]
Date: Fri, 30 Sep 2022 13:35:01 +0000 [thread overview]
Message-ID: <YzbwhXJnQQPpFm7Q@google.com> (raw)
In-Reply-To: <202209301338.aca913c3-yujie.liu@intel.com>
On Fri, Sep 30, 2022, kernel test robot wrote:
> Greeting,
>
> FYI, we noticed the following commit (built with gcc-11):
>
> commit: 7055fb11311622852c16463b1ccaa59e7691e42e ("KVM: x86: Treat pending TRIPLE_FAULT requests as pending exceptions")
> https://git.kernel.org/cgit/virt/kvm/kvm.git queue
...
> # ==== Test Assertion Failure ====
> # x86_64/mmio_warning_test.c:117: warnings_before == warnings_after
...
> [ 100.924976][ T4704] ------------[ cut here ]------------
> [ 100.931287][ T4704] WARNING: CPU: 67 PID: 4704 at arch/x86/kvm/x86.c:9934 inject_pending_event+0x6e6/0xe00 [kvm]
> [ 101.237320][ T4704] Call Trace:
> [ 101.241522][ T4704] <TASK>
> [ 101.245343][ T4704] vcpu_enter_guest+0x61a/0x3540 [kvm]
> [ 101.271009][ T4704] vcpu_run+0xbe/0x780 [kvm]
> [ 101.282791][ T4704] kvm_arch_vcpu_ioctl_run+0x334/0x1540 [kvm]
> [ 101.289810][ T4704] kvm_vcpu_ioctl+0x455/0xb00 [kvm]
> [ 101.359680][ T4704] __x64_sys_ioctl+0x128/0x1c0
> [ 101.365052][ T4704] do_syscall_64+0x38/0xc0
> [ 101.370066][ T4704] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [ 101.376647][ T4704] RIP: 0033:0x7f2a78126547
Good ol' emulated real mode. The warning exists to assert that KVM didn't queue
a new exception while injecting events, but when emulating Real Mode due to lack
of unrestricted guest, KVM needs to emulate the actual event injection and so can
trigger triple fault.
Ideally the assertion would filter out this exact case, but rmode.vm86_active is
buried in vcpu_vmx. Easiest thing is to just exempt KVM_REQ_TRIPLE_FAULT.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eb9d2c23fb04..1d02cc416cbc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9972,7 +9972,15 @@ static int kvm_check_and_inject_events(struct kvm_vcpu *vcpu,
kvm_x86_ops.nested_ops->has_events(vcpu))
*req_immediate_exit = true;
- WARN_ON(kvm_is_exception_pending(vcpu));
+ /*
+ * KVM should never attempt to queue a new exception while injecting an
+ * event, at this point KVM is done emulating and should only propagate
+ * the exception to the VMCS/VMCB. Exempt triple faults as VMX without
+ * unrestricted guest needs to emulate Real Mode events and queues a
+ * triple fault if injection fails (see kvm_inject_realmode_interrupt()).
+ */
+ WARN_ON_ONCE(vcpu->arch.exception.pending ||
+ vcpu->arch.exception_vmexit.pending);
return 0;
out:
next prev parent reply other threads:[~2022-09-30 13:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-30 6:12 [KVM] 7055fb1131: WARNING:at_arch/x86/kvm/x86.c:#inject_pending_event[kvm] kernel test robot
2022-09-30 13:35 ` Sean Christopherson [this message]
2022-09-30 13:35 ` Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YzbwhXJnQQPpFm7Q@google.com \
--to=seanjc@google.com \
--cc=lkp@lists.01.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.