Re: [PATCH v1 3/4] hw/arm/virt-acpi-build: patch guest SRAT for NUMA nodes

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Mon, 25 Sep 2023 11:03:28 -0300
Jason Gunthorpe <jgg@nvidia.com> wrote:

> On Mon, Sep 25, 2023 at 02:54:40PM +0100, Jonathan Cameron wrote:
> 
> > Possible the ASWG folk would say this is fine and I'm reading too much into
> > the spec, but I'd definitely suggest asking them via the appropriate path,
> > or throwing in a code first proposal for a comment on this special case and
> > see what response you get - my guess is it will be 'fix Linux' :(  
> 
> The goal here is for qemu to emulate what the bare metal environment
> is doing.
> 
> There may be a legitimate question if what the bare metal FW has done
> is legitimate (though let's face it, there are lots of creative ACPI
> things around), but I don't quite see how this is a qemu question?
> 
> Unless you are taking the position that qemu should not emulate this
> HW?

Ok. I'd failed to register that the bare metal code was doing this though
with hindsight I guess that is obvious. Though without more info or
a bare metal example being given its also possible the BIOS was doing
enumeration etc (like CXL does for all < 2.0 devices) and hence was
building SRAT with the necessary memory ranges in place - even if the
driver then does the hot add dance later.

That's dubious and likely to break at some point unless the spec
comprehends this use case, but meh, so are lots of other things and
the hardware vendor gets to pick up the pieces and deal with grumpy
customers.

I don't currently see this as a safe solution for the proposed other
use cases however that are virtualization only.

Jonathan

> 
> Jason