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Date: Sat, 09 Sep 2006 14:10:01 +0200
From: Fabrice Bellard <fabrice@bellard.org>
Subject: Re: [Qemu-devel] PCI Bios fixup
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To: samuel.thibault@ens-lyon.org
Cc: guillem@debian.org, qemu-devel@nongnu.org

Right, this is better. An even better fix would be to clear CS.RPL 
before the popf.

Regards,

Fabrice.

Samuel Thibault wrote:
> Hi,
> 
> The patch that qemu applies to bochs bios is a bit bugged:
> 
>  pci_pro_fail:
>    pop edi
>    pop esi
> -  sti
>    popf
>    stc
> +  and dword ptr[esp+4],0xfffffffc ;; reset CS.RPL for kqemu
>    retf
> 
> The and operation clears carry... So that pci functions always leave
> carry clear, and hence tell operating systems that they always work...
> This should rather be:
> 
>  pci_pro_fail:
>    pop edi
>    pop esi
> -  sti
>    popf
> +  and dword ptr[esp+4],0xfffffffc ;; reset CS.RPL for kqemu
>    stc
>    retf
> 
> Samuel
> 
> 
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