On Thu, Oct 09, 2025 at 12:01:26PM +0200, Gerd Hoffmann wrote:
> On Thu, Oct 09, 2025 at 01:24:24AM -0400, Chris Murphy wrote:
> > 
> > XBOOTLDR is being formatted either ext4 or XFS for a while now in Fedora.
> > 
> > UEFI spec supports file system drivers.
> 
> Yea, and tianocore even has a ext4 driver (see edk2-ext4.rpm and
> https://github.com/tianocore/edk2-platforms/tree/master/Features/Ext4Pkg).
> 
> But that helps how exactly?
> 
> vfat is the only filesystem required by the spec, so that is the one you
> can rely on being universally supported.  The ESP must be vfat anyway.
> 
> You could place the ext4 driver on the ESP.  Problem one is this is
> fragile.  You must arrange for the driver getting loaded.  Either via
> UEFI boot configuration (aka efi variables) which may get lost, or using
> bootloader specific ways to do so.  Problem two is the drivers are not
> signed, so with secure boot turned on this will not work.
> 
> I could bake the driver into tho OVMF firmware images.  That would get
> us around the secure boot signature requirement.  This obviously would
> work for virtual machines only, not your laptop.  It would make virtual
> machines have slightly different behavior than bare metal machines,
> which can be a source of obscure bugs.  Also virtual machines do not
> really need XBOOTLDR, you rarely have to deal with an existing ESP which
> is too small, so you can just make the ESP big enough on your images and
> be done with it.

Even if baked into OVMF upstream, we can't assume all public clouds will
honour that config choice in the UEFI firmware they offer. So it is only
a partial solution for VMs.

With regards,
Daniel
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