linux-kernel - RE: [PATCH v4] video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V host

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Message-ID: <PU1P153MB0169E5FA3D359C6BDD50EC34BF8C0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Mon, 16 Sep 2019 21:45:36 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Michael Kelley <mikelley@...rosoft.com>,
        Wei Hu <weh@...rosoft.com>,
        "b.zolnierkie@...sung.com" <b.zolnierkie@...sung.com>,
        "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>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>
CC:     Iouri Tarassov <iourit@...rosoft.com>
Subject: RE: [PATCH v4] video: hyperv: hyperv_fb: Obtain screen resolution
 from Hyper-V host

> From: linux-hyperv-owner@...r.kernel.org
> <linux-hyperv-owner@...r.kernel.org> On Behalf Of Dexuan Cui
> Sent: Thursday, September 12, 2019 11:39 PM
> To: Michael Kelley <mikelley@...rosoft.com>; Wei Hu <weh@...rosoft.com>;
> b.zolnierkie@...sung.com; linux-hyperv@...r.kernel.org;
> dri-devel@...ts.freedesktop.org; linux-fbdev@...r.kernel.org;
> linux-kernel@...r.kernel.org; Stephen Hemminger
> <sthemmin@...rosoft.com>; sashal@...nel.org; Haiyang Zhang
> <haiyangz@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>
> Cc: Iouri Tarassov <iourit@...rosoft.com>
> Subject: RE: [PATCH v4] video: hyperv: hyperv_fb: Obtain screen resolution
> from Hyper-V host
> 
> > From: Michael Kelley <mikelley@...rosoft.com>
> > Sent: Thursday, September 5, 2019 7:06 AM
> >
> > From: Wei Hu <weh@...rosoft.com> Sent: Thursday, September 5, 2019
> 2:12
> > AM
> > >
> > > Beginning from Windows 10 RS5+, VM screen resolution is obtained from
> > host.
> > > The "video=hyperv_fb" boot time option is not needed, but still can be
> > > used to overwrite what the host specifies. The VM resolution on the host
> > > could be set by executing the powershell "set-vmvideo" command.
> > >
> > > Signed-off-by: Iouri Tarassov <iourit@...rosoft.com>
> > > Signed-off-by: Wei Hu <weh@...rosoft.com>
> > > ---
> > >     v2:
> > >     - Implemented fallback when version negotiation failed.
> > >     - Defined full size for supported_resolution array.
> > >
> > >     v3:
> > >     - Corrected the synthvid major and minor version comparison
> problem.
> > >
> > >     v4:
> > >     - Changed function name to synthvid_ver_ge().
> > >
> > >  drivers/video/fbdev/hyperv_fb.c | 159
> > +++++++++++++++++++++++++++++---
> > >  1 file changed, 147 insertions(+), 12 deletions(-)
> > >
> >
> > Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
> 
> Looks good to me.
> 
> Reviewed-by: Dexuan Cui <decui@...rosoft.com>

Hi Wei,
It turns out we need to make a further fix. :-)

The patch forgets to take par->update into consideration.

When the VM Connection window is closed (or minimized?),
the host sends a message to the guest, and the guest sets
par->update to false in synthvid_recv_sub().

If par->update is false, the guest doesn't need to call
synthvid_update().

Thanks,
-- Dexuan