Re: [Qemu-devel] Re: [PATCH 2/3] qemu: make cirrus init value pci spec compliant

[Michael S. Tsirkin]

On Sun, Oct 11, 2009 at 04:39:46PM +0200, Gleb Natapov wrote:
> On Sun, Oct 11, 2009 at 04:35:35PM +0200, Michael S. Tsirkin wrote:
> > On Sun, Oct 11, 2009 at 03:57:48PM +0200, Gleb Natapov wrote:
> > > On Sun, Oct 11, 2009 at 03:52:40PM +0200, Michael S. Tsirkin wrote:
> > > > On Sun, Oct 11, 2009 at 03:45:59PM +0200, Gleb Natapov wrote:
> > > > > On Sun, Oct 11, 2009 at 03:36:26PM +0200, Michael S. Tsirkin wrote:
> > > > > > > No, I think Avi was right the first time.
> > > > > > > 
> > > > > > > Migrating from an older qemu will be fine at first, but at the 
> > > > > > > next
> > > > > > > reset _following_ migration, it'll be running the old BIOS on a 
> > > > > > > new
> > > > > > > qemu and fail.
> > > > > > > 
> > > > > > > -- Jamie
> > > > > > 
> > > > > > So after discussion with Gleb, it seems that what will happen
> > > > > > after migration to new qemu, old BIOS is shadowed, but memory
> > > > > > is already enabled.  After reset, new BIOS will be shadowed
> > > > > > and it will enable memory. Makes sense?
> > > > > > 
> > > > > I don't see how you made this conclusion after the discussion.
> > > > > What should happen is after migration old bios should be used until 
> > > > > reboot.
> > > > > After reboot new bios should be used.
> > > > 
> > > > I think that's what I said.
> > > > 
> > > First shadowing bios has nothing to do with it. Second what do you mean
> > > by "will happen"? That is how code works now or that is how it should
> > > work?  I am not sure this is how it works.
> > 
> > No, this is not how it works, I think.
> > Currently BIOS ROM is loaded only on init, directly into qemu memory.
> And have you checked if it is transfered to destination on migrate?
> 
> > BTW, I don't think it's write-protected and it probably should be?
> > 
> AFAIR it is not writable on plain qemu.

What makes it non-writeable?
It goes:
    bios_offset = qemu_ram_alloc(bios_size);
    ret = load_image(filename, qemu_get_ram_ptr(bios_offset));
Does qemu_ram_alloc allocate read-only memory then?

> --
>                       Gleb.