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From: Michael Kelley <mikelley@microsoft.com>
To: Wei Hu <weh@microsoft.com>,
	"rdunlap@infradead.org" <rdunlap@infradead.org>,
	"shc_work@mail.ru" <shc_work@mail.ru>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"lee.jones@linaro.org" <lee.jones@linaro.org>,
	"alexandre.belloni@bootlin.com" <alexandre.belloni@bootlin.com>,
	"baijiaju1990@gmail.com" <baijiaju1990@gmail.com>,
	"fthain@telegraphics.com.au" <fthain@telegraphics.com.au>,
	"info@metux.net" <info@metux.net>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"sashal@kernel.org" <sashal@kernel.org>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	KY Srinivasan <kys@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>
Subject: RE: [PATCH v5] video: hyperv: hyperv_fb: Support deferred IO for Hyper-V frame buffer driver
Date: Fri, 13 Sep 2019 23:31:42 +0000
Message-ID: <DM5PR21MB013732C4B83792CB49AC27A6D7B30@DM5PR21MB0137.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20190913060209.3604-1-weh@microsoft.com>

From: Wei Hu <weh@microsoft.com> Sent: Thursday, September 12, 2019 11:03 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@microsoft.com>
> ---
>     v2: Incorporated review comments from Michael Kelley
>     - Increased dirty rectangle by one row in deferred IO case when sending
>     to Hyper-V.
>     - Corrected the dirty rectangle size in the text mode.
>     - Added more comments.
>     - Other minor code cleanups.
> 
>     v3: Incorporated more review comments
>     - Removed a few unnecessary variable tests
> 
>     v4: Incorporated test and review feedback from Dexuan Cui
>     - Not disable interrupt while acquiring docopy_lock in
>       hvfb_update_work(). This avoids significant bootup delay in
>       large vCPU count VMs.
> 
>     v5: Completely remove the unnecessary docopy_lock after discussing
>     with Dexuan Cui.
> 

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

      parent reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-13  6:02 Wei Hu
2019-09-13  6:37 ` Dexuan Cui
2019-09-13 23:31 ` Michael Kelley [this message]

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