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Date: Mon, 18 Oct 2010 13:39:38 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 1/2] pci: Automatically patch PCI device
	id in PCI ROM
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, seabios@seabios.org, QEMU Developers <qemu-devel@nongnu.org>, Markus Armbruster <armbru@redhat.com>

On 10/18/2010 05:09 AM, Gerd Hoffmann wrote:
> On 10/15/10 23:05, Anthony Liguori wrote:
>> On 10/15/2010 03:51 PM, Stefan Weil wrote:
>>> PCI device with different device ids sometimes share
>>> the same rom code. Only the device id and the checksum
>>> differ in a boot rom for such devices.
>>
>> BTW, SeaBIOS doesn't reject ROMs when they're loaded via rombar, only
>> when they're loaded via romfile.
>
> SeaBIOS rejects them when loaded from the rom bar and doesn't reject 
> them when loaded via fw_cfg.

What I meant was, rombar=0 in qdev.  Sometimes my fingers don't work the 
same way my brain does :-)

> Using the rom bar is the prefered way though, fw_cfg is only there for 
> compatibility with older versions.
>
>> Maybe it's better to use fw_cfg to explicitly tell SeaBIOS to ignore the
>> PCI device id in the rom header for a certain device?
>
> Patching the rom is fine IMHO.  Why create + use a separate 
> communication path when we can use a much simpler approach?

How does this interact with PCI device passthrough?

We clearly can't patch in that case whereas if we had a hint to SeaBIOS, 
it would still work.

Regards,

Anthony Liguori

> cheers,
>   Gerd
>