linux-kernel - Re: [PATCH 1/1] fbdev/hyperv_fb: Fix logic error for Gen2 VMs in hvfb

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Message-ID: <20240203080850.GA29113@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Sat, 3 Feb 2024 00:08:50 -0800
From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To: mhklinux@...look.com
Cc: haiyangz@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
	drawat.floss@...il.com, javierm@...hat.com, deller@....de,
	daniel@...ll.ch, airlied@...il.com, tzimmermann@...e.de,
	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org
Subject: Re: [PATCH 1/1] fbdev/hyperv_fb: Fix logic error for Gen2 VMs in
 hvfb_getmem()

On Wed, Jan 31, 2024 at 10:00:22PM -0800, mhkelley58@...il.com wrote:
> From: Michael Kelley <mhklinux@...look.com>
> 
> A recent commit removing the use of screen_info introduced a logic
> error. The error causes hvfb_getmem() to always return -ENOMEM
> for Generation 2 VMs. As a result, the Hyper-V frame buffer
> device fails to initialize. The error was introduced by removing
> an "else if" clause, leaving Gen2 VMs to always take the -ENOMEM
> error path.
> 
> Fix the problem by removing the error path "else" clause. Gen 2
> VMs now always proceed through the MMIO memory allocation code,
> but with "base" and "size" defaulting to 0.
> 
> Fixes: 0aa0838c84da ("fbdev/hyperv_fb: Remove firmware framebuffers with aperture helpers")
> Signed-off-by: Michael Kelley <mhklinux@...look.com>
> ---
>  drivers/video/fbdev/hyperv_fb.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
> index c26ee6fd73c9..8fdccf033b2d 100644
> --- a/drivers/video/fbdev/hyperv_fb.c
> +++ b/drivers/video/fbdev/hyperv_fb.c
> @@ -1010,8 +1010,6 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
>  			goto getmem_done;
>  		}
>  		pr_info("Unable to allocate enough contiguous physical memory on Gen 1 VM. Using MMIO instead.\n");
> -	} else {
> -		goto err1;
>  	}
>  
>  	/*
> -- 
> 2.25.1
>
Reviewed-by: Saurabh Sengar <ssengar@...ux.microsoft.com>