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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Jason Wang <jasowang@redhat.com>,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, f.hetzelt@tu-berlin.de,
        david.kaplan@amd.com, konrad.wilk@oracle.com,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will@kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        "Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH 7/9] virtio-pci: harden INTX interrupts
In-Reply-To: <20210913175428-mutt-send-email-mst@kernel.org>
References: <20210913055353.35219-1-jasowang@redhat.com>
 <20210913055353.35219-8-jasowang@redhat.com> <875yv4f99j.ffs@tglx>
 <20210913175428-mutt-send-email-mst@kernel.org>
Date:   Tue, 14 Sep 2021 00:20:02 +0200
Message-ID: <87y280dsod.ffs@tglx>
MIME-Version: 1.0
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On Mon, Sep 13 2021 at 18:01, Michael S. Tsirkin wrote:
> On Mon, Sep 13, 2021 at 11:36:24PM +0200, Thomas Gleixner wrote:
>> >From the interrupt perspective the sequence:
>> 
>>         disable_irq();
>>         vp_dev->intx_soft_enabled = true;
>>         enable_irq();
>> 
>> is perfectly fine as well. Any interrupt arriving during the disabled
>> section will be reraised on enable_irq() in hardware because it's a
>> level interrupt. Any resulting failure is either a hardware or a
>> hypervisor bug.
>
> yes but it's a shared interrupt. what happens if multiple callers do
> this in parallel?

Nothing as each caller is serialized vs. itself and its own interrupt
handler it cares about.

Thanks,

        tglx