Re: [Xen-devel] qemu-xen-dir + PCI passthrough = BOOM

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Ian Campbell
> Sent: Thursday, December 19, 2013 12:13 AM
> To: Konrad Rzeszutek Wilk
> Cc: Anthony PERARD; xen-devel@xxxxxxxxxxxxxxxxxxxx;
> stefano.stabellini@xxxxxxxxxx
> Subject: Re: [Xen-devel] qemu-xen-dir + PCI passthrough = BOOM
> 
> On Wed, 2013-12-18 at 10:22 -0500, Konrad Rzeszutek Wilk wrote:
> > load_roms and bios_load are not set - so it wouldn't even do it.
> > It only does it for Bochs BIOS.
> 
> Right, this is deliberate.
> 
> For ROMBIOS (AKA BOchs BIOS) hvmloader loads the options roms. and I
> think ROMBIOS subsequently loads them.
> 
> For SeaBIOS it is the BIOS itself which both loads and executes the
> ROMS, which is why it is NULL in hvmloader.
> 
> The SeaBIOS way is far more like how systems normally work and because
> the BIOS is in charge it can do a better job than splitting it between
> two entities.
> 

I am also interested in this thread. Do you know why ROMBIOS doesn't handle
option ROM the same way as seaBIOS? Is there any special case that ROMBIOS
cannot handle? Thanks!

> Seems like perhaps I was mistaken about hvmloader+rombios not supporting
> loading from the ROM BAR of the device, it does seem to have some
> limited support for that (serial controllers and disk controllers only)
> 
> hvmloader+rombios does hardcode the VGA bios (rather than getting it
> from the emulated devices ROM bar), which is probably what I was
> thinking of, that's why people doing VGA passthrough with rombios need
> to grab the bios image and build it into hvmloader.
> 
> hvmloader+rombios also hardcodes the etherboot rom.
> 
> Ian.
> 
> 
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Thanks,
Feng

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