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

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Message-ID: <PU1P153MB0169811097EA55DF795888B2BF9C0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Wed, 2 Oct 2019 08:09:41 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Sasha Levin <sashal@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>
CC:     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

> -----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

I can apply the 2 patches on the hyperv-next branch (the top commit is 48b72a2697d5):

[decui@...alhost linux]$ patch -p1 < 1.diff
patching file drivers/video/fbdev/hyperv_fb.c
Hunk #2 succeeded at 53 (offset 1 line).
Hunk #3 succeeded at 95 (offset 1 line).
Hunk #4 succeeded at 124 (offset 1 line).
Hunk #5 succeeded at 222 (offset 1 line).
Hunk #6 succeeded at 262 (offset 2 lines).
Hunk #7 succeeded at 394 (offset 2 lines).
Hunk #8 succeeded at 441 (offset 2 lines).
Hunk #9 succeeded at 480 (offset 2 lines).
Hunk #10 succeeded at 558 (offset 2 lines).
Hunk #11 succeeded at 590 (offset 2 lines).
Hunk #12 succeeded at 785 (offset 2 lines).
Hunk #13 succeeded at 823 (offset 2 lines).

[decui@...alhost linux]$ patch -p1 < 2.diff
patching file drivers/video/fbdev/Kconfig
Hunk #1 succeeded at 2214 (offset -27 lines).
patching file drivers/video/fbdev/hyperv_fb.c
Hunk #1 succeeded at 238 (offset 1 line).
Hunk #2 succeeded at 259 (offset 2 lines).
Hunk #3 succeeded at 277 (offset 2 lines).
Hunk #4 succeeded at 364 (offset 2 lines).
Hunk #5 succeeded at 692 (offset 2 lines).
Hunk #6 succeeded at 702 (offset 2 lines).
Hunk #7 succeeded at 719 (offset 2 lines).
Hunk #8 succeeded at 801 (offset 2 lines).
Hunk #9 succeeded at 863 (offset 2 lines).
Hunk #10 succeeded at 876 (offset 2 lines).
Hunk #11 succeeded at 889 (offset 2 lines).
Hunk #12 succeeded at 951 (offset 2 lines).
Hunk #13 succeeded at 988 (offset 2 lines).
Hunk #14 succeeded at 1007 (offset 2 lines).
Hunk #15 succeeded at 1041 (offset 2 lines).

Thanks,
-- Dexuan