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

[Laszlo Ersek]

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.

Laszlo