linux-kernel - RE: [PATCH v4 2/2] hyperv-fb: kick off efifb early

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Date:	Tue, 25 Feb 2014 15:51:15 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Gerd Hoffmann <kraxel@...hat.com>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	KY Srinivasan <kys@...rosoft.com>,
	"Abhishek Gupta (LIS)" <abgupta@...rosoft.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"tomi.valkeinen@...com" <tomi.valkeinen@...com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
Subject: RE: [PATCH v4 2/2] hyperv-fb: kick off efifb early



> -----Original Message-----
> From: Gerd Hoffmann [mailto:kraxel@...hat.com]
> Sent: Tuesday, February 25, 2014 7:29 AM
> To: linux-fbdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org; gregkh@...uxfoundation.org; KY Srinivasan;
> Abhishek Gupta (LIS); Haiyang Zhang; jasowang@...hat.com;
> tomi.valkeinen@...com; devel@...uxdriverproject.org; Gerd Hoffmann; Jean-
> Christophe Plagniol-Villard
> Subject: [PATCH v4 2/2] hyperv-fb: kick off efifb early
> 
> Remove firmware framebuffer before initializing hyperv-fb.  Needed
> on gen2 virtual machines.   Letting register_framebuffer handle the
> switchover results in efifb still being active while hyperv graphics are
> initialized, which in turn can make the linux kernel hang.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/video/hyperv_fb.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/video/hyperv_fb.c b/drivers/video/hyperv_fb.c index
> b7b3dd0..1b11886 100644
> --- a/drivers/video/hyperv_fb.c
> +++ b/drivers/video/hyperv_fb.c
> @@ -683,6 +683,7 @@ static int hvfb_getmem(struct fb_info *info)
>  		info->apertures->ranges[0].base = pci_resource_start(pdev, 0);
>  		info->apertures->ranges[0].size = pci_resource_len(pdev, 0);
>  	}
> +	remove_conflicting_framebuffers(info->apertures,
> KBUILD_MODNAME,
> +false);

Thanks for the updates. I'm concerned about, after removing efifb, 
if synthvid_send_config(hdev) fails, then there will be no video driver
available. Is there a way to bring the generic driver back if 
synthvid_send_config(hdev) fails?

If no way to recover the generic driver, please limit the early
remove_conflicting_framebuffers() to Gen2 VM only.

Thanks,
- Haiyang

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