linux-kernel - Re: [PATCH] x86/efi: Fix multiple GOP device support

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Message-ID: <20151014144715.GA17890@gmail.com>
Date:	Wed, 14 Oct 2015 16:47:15 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Kővágó, Zoltán <dirty.ice.hu@...il.com>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Matthew Garrett <mjg59@...f.ucam.org>, stable@...r.kernel.org,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH] x86/efi: Fix multiple GOP device support


* Matt Fleming <matt@...eblueprint.co.uk> wrote:

> From: Kővágó, Zoltán <dirty.ice.hu@...il.com>
> 
> When multiple GOP devices exists, but none of them implements ConOut,
> the code should just choose the first GOP (according to the comments).
> But currently fb_base will refer to the last GOP, while other parameters
> to the first GOP, which will likely result in a garbled display.
> 
> I can reliably reproduce this bug using my ASRock Z87M Extreme4
> motherboard with CSM and integrated GPU disabled, and two PCIe video
> cards (NVidia GT640 and GTX980), booting from efi-stub (booting from
> grub works fine).  On the primary display the asrock logo remains and on
> the secondary screen is garbled up completely.
> 
> Signed-off-by: Kővágó, Zoltán <DirtY.iCE.hu@...il.com>
> Cc: Matthew Garrett <mjg59@...f.ucam.org>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Matt Fleming <matt.fleming@...el.com>
> ---
>  arch/x86/boot/compressed/eboot.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index ee1b6d346b98..db51c1f27446 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -667,6 +667,7 @@ setup_gop32(struct screen_info *si, efi_guid_t *proto,
>  		bool conout_found = false;
>  		void *dummy = NULL;
>  		u32 h = handles[i];
> +		u32 current_fb_base;

Sigh, fb_base is u64...

> @@ -770,6 +772,7 @@ setup_gop64(struct screen_info *si, efi_guid_t *proto,
>  		bool conout_found = false;
>  		void *dummy = NULL;
>  		u64 h = handles[i];
> +		u32 current_fb_base;

Ditto.

So I've applied it with that obvious bug fixed, but could you guys please double 
check how on earth this patch could possibly have worked fine in testing, without 
crashing 64-bit kernels?

Thanks,

	Ingo
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