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Date:   Thu, 19 Dec 2019 07:57:46 -0800
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Frederic Weisbecker <frederic@kernel.org>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org
Subject: Re: Async page fault delivered while irq are disabled?
Message-ID: <20191219155745.GA6439@linux.intel.com>
References: <20191219152814.GA24080@lenoir>
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On Thu, Dec 19, 2019 at 04:28:15PM +0100, Frederic Weisbecker wrote:
> Hi,
> 
> While checking the x86 async page fault code, I can't
> find anything that prevents KVM_PV_REASON_PAGE_READY to be injected
> while the guest has interrupts disabled. If that page fault happens
> to trap in an interrupt disabled section, there may be a deadlock due to the
> call to wake_up_process() which locks the rq->lock (among others).
> 
> Given how long that code is there, I guess such an issue would
> have been reported for a while already. But I just would like to
> be sure we are checking that.
> 
> Can someone enlighten me?

The check is triggered from the caller of kvm_async_page_present().

kvm_check_async_pf_completion()
|
|-> kvm_arch_can_inject_async_page_present()
    |
    |-> kvm_can_do_async_pf()
        |
        |-> kvm_x86_ops->interrupt_allowed()