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


From: Laszlo Ersek
Subject: Re: [Qemu-devel] [SeaBIOS] [edk2] (PAM stuff) reset doesn't work on OVMF + SeaBIOS CSM
Date: Mon, 18 Feb 2013 20:39:34 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130108 Thunderbird/10.0.12

On 02/18/13 20:09, Laszlo Ersek wrote:
> On 02/18/13 20:00, Kevin O'Connor wrote:
>> On Mon, Feb 18, 2013 at 08:31:01PM +0200, Gleb Natapov wrote:
>>> Laszlo explained to me that the problem is that after reset we end up
>>> in SeaBIOS reset code instead of OVMF one. This is because kvm starts
>>> to execute from ffff0 instead of fffffff0 after reset and this memory
>>> location is modifying during CSM loading. Seabios solves this problem
>>> by detecting reset condition and copying pristine image of itself from
>>> the end of 4G to the end of 1M. OVMF should do the same, but with CSM
>>> it does not get control back after reset since Seabios reset vector is
>>> executed instead. Why not put OVMF reset code at reset vector in CSM
>>> built SeaBIOS to solve the problem?
>>
>> Why not fix KVM so that it runs at fffffff0 after reset?
>>
>> The only thing SeaBIOS could do is setup the segment registers and
>> then jump to fffffff0, which is a bit of work for the same end result.
> 
> Gleb told me to test under a kvm/next host kernel; there have been many
> real-mode related commits. I'll report back.

I built a host kernel from
<http://git.kernel.org/?p=virt/kvm/kvm.git;a=shortlog;h=refs/heads/next>, 
currently
at commit cbd29cb6.

The guest reboot works now. :)

Thanks all!
Laszlo



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