linux-kernel - Re: [PATCH v2] x86:sysfb_efi:efifb_set_system: fix miss valid address range in later BARs

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Date:	Mon, 2 May 2016 15:11:20 -0400
From:	Peter Jones <pjones@...hat.com>
To:	Wang YanQing <udknight@...il.com>
Cc:	Matt Fleming <matt@...eblueprint.co.uk>, x86@...nel.org,
	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	dh.herrmann@...il.com, tomi.valkeinen@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86:sysfb_efi:efifb_set_system: fix miss valid
 address range in later BARs

On Sun, May 01, 2016 at 12:21:05AM +0800, Wang YanQing wrote:
> We can't just break out when meet start is equal to zero,
> this will cause we miss valid address range in later BARs.
> 
> On the other hand, it isn't enough to test start only
> for below situation:
> 0(start) <= lfb_base < end
> 
> Note: this patch also add a trivial optimization,
>       break out after we find the address range
>       is valid without test later BARs.
> 
> Signed-off-by: Wang YanQing <udknight@...il.com>

This looks correct to me:

Reviewed-By: Peter Jones <pjones@...hat.com>

Cc'ing Matt Fleming, since this should probably go through the EFI tree.

> ---
>  Due to the BUG this patch fix, I can't use video=efifb:
>  boot parameter to get efifb on my new ThinkPad E550 for
>  my old linux system hard disk with 3.10 kernel. In 3.10, 
>  efifb is the only choice due to DRM/I915 in it doesn't 
>  support the GPU.
> 
>  Changes:
>  v1-v2:
>  1: Do a trivial code optimization.
> 
>  arch/x86/kernel/sysfb_efi.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/sysfb_efi.c b/arch/x86/kernel/sysfb_efi.c
> index b285d4e..5da924b 100644
> --- a/arch/x86/kernel/sysfb_efi.c
> +++ b/arch/x86/kernel/sysfb_efi.c
> @@ -106,14 +106,24 @@ static int __init efifb_set_system(const struct dmi_system_id *id)
>  					continue;
>  				for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
>  					resource_size_t start, end;
> +					unsigned long flags;
> +
> +					flags = pci_resource_flags(dev, i);
> +					if (!(flags & IORESOURCE_MEM))
> +						continue;
> +
> +					if (flags & IORESOURCE_UNSET)
> +						continue;
> +
> +					if (pci_resource_len(dev, i) == 0)
> +						continue;
>  
>  					start = pci_resource_start(dev, i);
> -					if (start == 0)
> -						break;
>  					end = pci_resource_end(dev, i);
>  					if (screen_info.lfb_base >= start &&
>  					    screen_info.lfb_base < end) {
>  						found_bar = 1;
> +						break;
>  					}
>  				}
>  			}
> -- 
> 1.8.5.6.2.g3d8a54e.dirty

-- 
  Peter