linux-kernel - Re: [PATCH v2] partially revert "xen: Remove event channel notification through Xen PCI platform device"

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Message-ID: <816b6ead-6de9-5076-12f1-798b8de080a4@oracle.com>
Date:   Fri, 13 Jan 2017 09:07:55 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Stefano Stabellini <sstabellini@...nel.org>
Cc:     jgross@...e.com, karahmed@...zon.de, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, konrad.wilk@...cle.com
Subject: Re: [PATCH v2] partially revert "xen: Remove event channel
 notification through Xen PCI platform device"

On 01/12/2017 04:39 PM, Stefano Stabellini wrote:
> The following commit:
>
> commit 72a9b186292d98494f222226cfd24a1621796209
> Author: KarimAllah Ahmed <karahmed@...zon.de>
> Date:   Fri Aug 26 23:55:36 2016 +0200
>
>     xen: Remove event channel notification through Xen PCI platform device
>
> broke Linux when booting as Dom0 on Xen in a nested Xen environment (Xen
> installed inside a Xen VM). In this scenario, Linux is a PV guest, but
> at the same time it uses the platform-pci driver to receive
> notifications from L0 Xen. vector callbacks are not available because L1
> Xen doesn't allow them.
>
> Partially revert the offending commit, by restoring IRQ based
> notifications for PV guests only. I restored only the code which is
> strictly needed and replaced the xen_have_vector_callback checks within
> it with xen_pv_domain() checks.
>
> Signed-off-by: Stefano Stabellini <sstabellini@...nel.org>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>