linux-kernel - Re: [PATCH 7/9] virtio-pci: harden INTX interrupts

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Message-ID: <87y280dsod.ffs@tglx>
Date:   Tue, 14 Sep 2021 00:20:02 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, f.hetzelt@...berlin.de,
        david.kaplan@....com, konrad.wilk@...cle.com,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH 7/9] virtio-pci: harden INTX interrupts

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