Re: [Qemu-devel] [PATCH 0/2] PC: improve emulation correctness

[Hervé Poussineau]

Le 05/03/2014 09:15, Paolo Bonzini a écrit :
> Il 05/03/2014 00:49, Michael S. Tsirkin ha scritto:
> > On Mon, Mar 03, 2014 at 11:05:17PM +0100, Hervé Poussineau wrote:
> > > Ping.
> > >
> > > QEMU crash at reboot is due to not resetting PAM registers at i440fx
> > > reset, but a patch has already been rejected on ML:
> > > http://lists.gnu.org/archive/html/qemu-devel/2013-02/msg02928.html
> > >
> > > Hervé
> >
> > I thought an alternative fix is being worked on?
> > http://lists.gnu.org/archive/html/qemu-devel/2013-02/msg02967.html
>
> Hervé, how does the BIOS do the reset?
>
> Paolo

At cold boot, BIOS is shadowed to RAM, and then hot-patched, so a warm boot 
won't do the same thing.
At BIOS exit, BIOS jumps to the new warm boot path.
This warm path doesn't work and crashes QEMU with "qemu: fatal: Trying to execute 
code outside RAM or ROM at 0x000a1249" ; I've no idea why exactly.
Resetting PAM registers prevents the shadowed copy to be visible, and BIOS does 
again a cold boot, which works.

Hervé