Re: GNTTABOP_setup_table yields -1 PFNs

[Taylor R Campbell <riastradh-xen-devel@xxxxxxxxxx>]

> Date: Mon, 8 Jul 2024 11:09:21 +0200
> From: Jan Beulich <jbeulich@xxxxxxxx>
> 
> On 06.07.2024 04:22, Taylor R Campbell wrote:
> > On a Xen 4.14 host (with extraversion=.0.88.g1d1d1f53), with version 1
> > grant tables, where GNTTABOP_query_size initially returns nr_frames=32
> > max_nr_frames=64, a NetBSD guest repeatedly queries
> > GNTTABOP_setup_table for successively larger nr_frames from 1 up.
> 
> First question: Is there some earlier GNTTABOP_setup_table that you invoke?
> I'd expect (and also observe) nr_frames=1 initially.

Not that the guest OS invokes.  Perhaps the bootloader, pv-grub 0.97,
might invoke GNTTABOP_setup_table?  I looked around but couldn't find
an obvious source for pv-grub 0.97.

> Second: The version you name is pretty unclear from an upstream perspective.
> Leaving aside that 4.14 is out of support, it's entirely unclear whether you
> at least have all bug fixes in place that we have upstream (4.14.6). Without
> that it's hard to see what you're asking for.

It looks like it's based on commit:

commit 1d1d1f5391976456a79daac0dcfe7157da1e54f7
Author: Roger Pau Monné <roge.rpau@xxxxxxxxxx>
Date:   Tue Dec 1 15:34:55 2020 +0100

    x86/vioapic: fix usage of index in place of GSI in vioapic_write_redirent

Does that help to narrow it down?  (I don't know if I can rule out
local changes, though.)