[PATHC v6] video: hyperv: hyperv_fb: Support deferred IO for Hyper-V frame buffer driver
sashal at kernel.org
Tue Oct 1 18:48:28 UTC 2019
On Fri, Sep 20, 2019 at 05:26:34PM +0000, Michael Kelley wrote:
>From: Michael Kelley <mikelley at microsoft.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 at microsoft.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?
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