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

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Date: Thu, 1 Feb 2024 09:17:18 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: mhklinux@...look.com, 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
Cc: 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()

Hi

Am 01.02.24 um 07:00 schrieb mhkelley58@...il.com:
> 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.

Indeed, that's how it was supposed to work. IDK how I didn't notice this 
bug. Thanks a lot for the fix.

> 
> Fixes: 0aa0838c84da ("fbdev/hyperv_fb: Remove firmware framebuffers with aperture helpers")
> Signed-off-by: Michael Kelley <mhklinux@...look.com>

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

> ---
>   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;
>   	}
>   
>   	/*

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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