linux-kernel - Re: [PATHC v6] video: hyperv: hyperv_fb: Support deferred IO for Hyper-V frame buffer driver

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Date:   Wed, 2 Oct 2019 08:40:02 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     Michael Kelley <mikelley@...rosoft.com>,
        Wei Hu <weh@...rosoft.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "shc_work@...l.ru" <shc_work@...l.ru>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "baijiaju1990@...il.com" <baijiaju1990@...il.com>,
        "info@...ux.net" <info@...ux.net>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>
Subject: Re: [PATHC v6] video: hyperv: hyperv_fb: Support deferred IO for
 Hyper-V frame buffer driver

On Wed, Oct 02, 2019 at 08:09:41AM +0000, Dexuan Cui wrote:
>> -----Original Message-----
>> From: Sasha Levin <sashal@...nel.org>
>> Sent: Tuesday, October 1, 2019 11:48 AM
>>
>> On Fri, Sep 20, 2019 at 05:26:34PM +0000, Michael Kelley wrote:
>> >From: Michael Kelley <mikelley@...rosoft.com>  Sent: Wednesday,
>> September 18, 2019 2:48 PM
>> >> >
>> >> > Without deferred IO support, hyperv_fb driver informs the host to refresh
>> >> > the entire guest frame buffer at fixed rate, e.g. at 20Hz, no matter there
>> >> > is screen update or not. This patch supports deferred IO for screens in
>> >> > graphics mode and also enables the frame buffer on-demand refresh. The
>> >> > highest refresh rate is still set at 20Hz.
>> >> >
>> >> > Currently Hyper-V only takes a physical address from guest as the starting
>> >> > address of frame buffer. This implies the guest must allocate contiguous
>> >> > physical memory for frame buffer. In addition, Hyper-V Gen 2 VMs only
>> >> > accept address from MMIO region as frame buffer address. Due to these
>> >> > limitations on Hyper-V host, we keep a shadow copy of frame buffer
>> >> > in the guest. This means one more copy of the dirty rectangle inside
>> >> > guest when doing the on-demand refresh. This can be optimized in the
>> >> > future with help from host. For now the host performance gain from
>> deferred
>> >> > IO outweighs the shadow copy impact in the guest.
>> >> >
>> >> > Signed-off-by: Wei Hu <weh@...rosoft.com>
>> >
>> >Sasha -- this patch and one other from Wei Hu for the Hyper-V frame buffer
>> >driver should be ready.  Both patches affect only the Hyper-V frame buffer
>> >driver so can go through the Hyper-V tree.  Can you pick these up?  Thx.
>>
>> I can't get this to apply anywhere, what tree is it based on?
>>
>> --
>> Thanks,
>> Sasha
>
>Hi Sasha,
>Today's hyperv/linux.git's hyperv-next branch's top commit is
>    48b72a2697d5 ("hv_netvsc: Add the support of hibernation").
>
>Please pick up two patches from Wei Hu:
>#1: [PATCH v4] video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V host
>#2: [PATHC v6] video: hyperv: hyperv_fb: Support deferred IO for Hyper-V frame buffer driver

Ah, I guess I was missing the first one. I've queued both for
hyperv-next, thanks!

--
Thanks,
Sasha