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Date:   Fri, 4 Jun 2021 19:52:54 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Dexuan Cui <decui@microsoft.com>
Cc:     'Wei Liu' <wei.liu@kernel.org>, vkuznets <vkuznets@redhat.com>,
        'Vineeth Pillai' <viremana@linux.microsoft.com>,
        "'dri-devel@lists.freedesktop.org'" <dri-devel@lists.freedesktop.org>,
        "'linux-hyperv@vger.kernel.org'" <linux-hyperv@vger.kernel.org>,
        "'linux-fbdev@vger.kernel.org'" <linux-fbdev@vger.kernel.org>,
        "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>,
        Michael Kelley <mikelley@microsoft.com>
Subject: Re: [bug report] Commit ccf953d8f3d6 ("fb_defio: Remove custom
 address_space_operations") breaks Hyper-V FB driver
Message-ID: <YLp2hulQpBl7JRSO@casper.infradead.org>
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On Fri, Jun 04, 2021 at 06:37:49PM +0000, Dexuan Cui wrote:
> > From: Dexuan Cui
> > Sent: Friday, June 4, 2021 11:17 AM
> > > >> ...
> > > > I've heard a similar report from Vineeth but we didn't get to the bottom
> > > > of this.
> > > I have just tried reverting the commit mentioned above and it solves the
> > > GUI freeze
> > > I was also seeing. Previously, login screen was just freezing, but VM
> > > was accessible
> > > through ssh. With the above commit reverted, I can login to Gnome.
> > >
> > > Looks like I am also experiencing the same bug mentioned here.
> > >
> > > Thanks,
> > > Vineeth
> > 
> > As Matthew mentioned, this is a known issue:
> > https://lwn.net/ml/linux-kernel/YLZEhv0cpZp8uVE3@casper.infradead.org/
> > 
> > Matthew has reverted ccf953d8f3d6:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=
> > 0b78f8bcf4951af30b0ae83ea4fad27d641ab617
> > so the latest mainline should work now.
> > 
> > Thanks,
> > Dexuan
> 
> Hi Matthew,
> With today's latest mainline 16f0596fc1d78a1f3ae4628cff962bb297dc908c,
> the Xorg works again in Linux VM on Hyper-V, but when I reboot the VM, I
> always see a lot of "BUG: Bad page state in process Xorg " warnings (there
> are about 60 such warnings) before the VM reboots.
> 
> BTW, I happen to have an older Mar-28 mainline kernel (36a14638f7c0654),
> which has the same warnings. 
> 
> Any idea which change introduced the warnings? 

Looks like someone forgot to call fb_deferred_io_cleanup()?