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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 2 Mar 2016 15:15:48 +0100
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Subject: Re: [Qemu-devel] [PATCH 18/38] ivshmem: Leave INTx alone when using
 MSI-X
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To: Markus Armbruster <armbru@redhat.com>
Cc: Claudio Fontana <claudio.fontana@huawei.com>, cam <cam@cs.ualberta.ca>, =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= <marcandre.lureau@gmail.com>, QEMU <qemu-devel@nongnu.org>, David Marchand <david.marchand@6wind.com>



On 02/03/2016 12:04, Markus Armbruster wrote:
> For better or worse, fallback to INTx has never been implemented in
> ivshmem.  You can either ask for an INTx-only device (msi=3Doff), or fo=
r
> an MSI-X-only device (msi=3Don).  The latter *cannot* do interrupts unt=
il
> you enable MSI-X.

Aha, now I see what you mean:

    if (ivshmem_has_feature(s, IVSHMEM_MSI)) {
        msix_notify(pdev, vector);
    } else {
        ivshmem_IntrStatus_write(s, 1);
    }

So I believe your patch is okay.  Perhaps you could also change the
interrupt pin for new machine types (even without changing the
revision), but it's not necessary to do it.

> Similarly, the ivshmem-doorbell device introduced later in this series
> can only do MSI-X, and the ivshmem-plain device cannot do interrupts at
> all.

Here:

    dev->config[PCI_INTERRUPT_PIN] =3D 0x01; /* interrupt pin 1 */

Paolo