Re: [Xen-devel] [RFC PATCH 0/5] Load BIOS via toolstack instead of been embedded in hvmloader.

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Wed, Sep 16, 2015 at 07:56:44PM +0100, Andrew Cooper wrote:
> On 16/09/2015 18:19, Anthony PERARD wrote:
> > Hi all,
> >
> > I've start to look at loading the BIOS and the ACPI tables via the
> > toolstack instead of having them embedded in the hvmloader binary. This is
> > done by using the same mechanics as the one used to load extra ACPI tables
> > or SMBIOS.
> >
> > - libxl load the blob into it's memory and add it to
> >   struct xc_hvm_build_args.bios_module
> > - libxc load the blob into the guest memory and give back the guest address
> >   of the blob.
> > - libxl store the location of the blob (and it's lenght) into xenstore, in
> >   /local/domain/$domid/hvmloader/$blob_name/{address,length} ($blob_name
> >   would be "bios" or "acpi_table"; there is already "acpi" and "smbios"
> >   that exist)
> > - hvmloader read the addresses from xenstore and put the blob at the right
> >   place.
> >
> > How this is looking?
> >
> > Right now, this patch series would only work for SeaBIOS.
> 
> I highly recommend that you build on top of Rogers DMlite series, which
> already offers a multiboot-style way of adding extra modules to HVM
> guests.  (That was the way I was planning to do this in some copious
> free time).

Thanks. I will look into this.

> In particular, storing the address/length in xenstore is conceptually
> incorrect as the information turns stale as soon as hvmloader starts
> running.
> 
> * Modify hvmloader to have a DMLite entry, which gives it a command line
> and module list
> * Modify libxc to be able to take an arbitrary quantity of modules,
> rather than the currently limit of 1
> 
> Once the above work times are in place, the actual splitting-up of
> hvmloader can occur.
> 
> I recommend a command line way of telling hvmloader which module is
> what, such as a legacy bios image, (other firmware image?), supplemental
> acpi table, supplemental smbios table, nvram blob?  (This last one will
> require a bit of extra work so the toolstack can pull the blob back out
> of the guest on destruction)

-- 
Anthony PERARD

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