linux-kernel - RE: [RFC PATCH v2 1/3] vfio: Use capability chains to handle device specific irq

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Date:   Thu, 6 Jun 2019 10:17:51 +0000
From:   "Zhang, Tina" <tina.zhang@...el.com>
To:     "kraxel@...hat.com" <kraxel@...hat.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        "Yuan, Hang" <hang.yuan@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "Lv, Zhiyuan" <zhiyuan.lv@...el.com>,
        "intel-gvt-dev@...ts.freedesktop.org" 
        <intel-gvt-dev@...ts.freedesktop.org>,
        "Wang, Zhi A" <zhi.a.wang@...el.com>
Subject: RE: [RFC PATCH v2 1/3] vfio: Use capability chains to handle device
 specific irq


> -----Original Message-----
> From: intel-gvt-dev [mailto:intel-gvt-dev-bounces@...ts.freedesktop.org] On
> Behalf Of kraxel@...hat.com
> Sent: Wednesday, June 5, 2019 6:10 PM
> To: Zhang, Tina <tina.zhang@...el.com>
> Cc: Tian, Kevin <kevin.tian@...el.com>; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; Zhenyu Wang <zhenyuw@...ux.intel.com>; Yuan,
> Hang <hang.yuan@...el.com>; alex.williamson@...hat.com; Lv, Zhiyuan
> <zhiyuan.lv@...el.com>; intel-gvt-dev@...ts.freedesktop.org; Wang, Zhi A
> <zhi.a.wang@...el.com>
> Subject: Re: [RFC PATCH v2 1/3] vfio: Use capability chains to handle device
> specific irq
> 
>   Hi,
> 
> > > Really need to split for different planes? I'd like a
> > > VFIO_IRQ_SUBTYPE_GFX_DISPLAY_EVENT
> > > so user space can probe change for all.
> 
> > User space can choose to user different handlers according to the
> > specific event. For example, user space might not want to handle every
> > cursor event due to performance consideration. Besides, it can reduce
> > the probe times, as we don't need to probe twice to make sure if both
> > cursor plane and primary plane have been updated.
> 
> I'd suggest to use the value passed via eventfd for that, i.e. instead of
> sending "1" unconditionally send a mask of changed planes.
If there is only one eventfd working for GFX_DISPLAY, should it be  VFIO_IRQ_INFO_EVENTFD and VFIO_IRQ_INFO_AUTOMASKED? i.e. after signaling, the interrupt is automatically masked and the user space needs to unmask the line to receive new irq event.

BR,
Tina


> 
> cheers,
>   Gerd
> 
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> intel-gvt-dev@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

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