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From:   Dexuan Cui <decui@microsoft.com>
To:     Sasha Levin <sashal@kernel.org>, Wei Hu <weh@microsoft.com>
CC:     Michael Kelley <mikelley@microsoft.com>,
        "rdunlap@infradead.org" <rdunlap@infradead.org>,
        "shc_work@mail.ru" <shc_work@mail.ru>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>
Subject: RE: [PATCH v5] video: hyperv: hyperv_fb: Support deferred IO for
 Hyper-V frame buffer driver
Thread-Topic: [PATCH v5] video: hyperv: hyperv_fb: Support deferred IO for
 Hyper-V frame buffer driver
Thread-Index: AQHVeIhjL2AndauzGUaHnigxWapFw6dG+x3A
Date:   Wed, 2 Oct 2019 07:52:27 +0000
Message-ID: <PU1P153MB0169724E7E7432F1100EE96ABF9C0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
References: <20190913060209.3604-1-weh@microsoft.com>
 <20191001184526.GE8171@sasha-vm>
In-Reply-To: <20191001184526.GE8171@sasha-vm>
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> From: Sasha Levin <sashal@kernel.org>
> Sent: Tuesday, October 1, 2019 11:45 AM
> To: Wei Hu <weh@microsoft.com>
>=20
> On Fri, Sep 13, 2019 at 06:02:55AM +0000, Wei Hu wrote:
> >Without deferred IO support, hyperv_fb driver informs the host to refres=
h
> >the entire guest frame buffer at fixed rate, e.g. at 20Hz, no matter the=
re
> >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 starti=
ng
> >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 defer=
red
> >IO outweighs the shadow copy impact in the guest.
> >
> >Signed-off-by: Wei Hu <weh@microsoft.com>
>=20
> What tree is this based on? I can't get it to apply.
>=20
> Thanks,
> Sasha

Please use Wei's v6 patch, which can apply on today's hyperv/linux.git/s hy=
perv-next branch.

Thanks,
-- Dexuan