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Re: [Qemu-devel] [edk2] (PAM stuff) reset doesn't work on OVMF + SeaBIOS


From: Laszlo Ersek
Subject: Re: [Qemu-devel] [edk2] (PAM stuff) reset doesn't work on OVMF + SeaBIOS CSM
Date: Thu, 14 Feb 2013 22:14:28 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130108 Thunderbird/10.0.12

On 02/14/13 21:54, H. Peter Anvin wrote:
> On 02/14/2013 12:41 PM, Laszlo Ersek wrote:
>>
>> ). cpu_reset() [target-i386/helper.c] sets CS:IP to f000:fff0, which is
>> the exact address of... reset_vector() in SeaBIOS.
>>
> 
> This would be a bug, but it isn't quite true.
> 
> If you look at x86_cpu_reset() you will note that it sets the code
> segment base to 0xffff0000, not 0xf0000 as one could expect from the
> above.  This is also true of a physical x86.
> 
> As such, the *real* reset vector is at 0xfffffff0 as opposed to the
> SeaBIOS vector at 0xffff0 -- this is a backwards compatibility vector
> which typically just issues a real reset.
> 
> Now, if Qemu doesn't handle the distinction here correctly, that is a bug.

I think I was simply wrong :)

Thanks
Laszlo



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