Re: [PATCH v2 6/7] xen: allow mapping ACPI data using a different physical address

[Juergen Gross <jgross@xxxxxxxx>]

On 20.08.24 11:56, Jan Beulich wrote:
> On 20.08.2024 10:20, Juergen Gross wrote:
> > @@ -838,6 +839,31 @@ void __init xen_do_remap_nonram(void)
> >         pr_info("Remapped %u non-RAM page(s)\n", remapped);
> >   }
> >   
> > +/*
> > + * Xen variant of acpi_os_ioremap() taking potentially remapped non-RAM
> > + * regions into acount.
> > + * Any attempt to map an area crossing a remap boundary will produce a
> > + * WARN() splat.
> > + */
> > +static void __iomem *xen_acpi_os_ioremap(acpi_physical_address phys,
> > +                                        acpi_size size)
> > +{
> > +       unsigned int i;
> > +       struct nonram_remap *remap = xen_nonram_remap;
> const (also in one of the functions in patch 5)?
Yes.

> > +       for (i = 0; i < nr_nonram_remap; i++) {
> > +               if (phys + size > remap->maddr &&
> > +                   phys < remap->maddr + remap->size) {
> > +                       WARN_ON(phys < remap->maddr ||
> > +                               phys + size > remap->maddr + remap->size);
> > +                       phys = remap->paddr + phys - remap->maddr;
> > +                       break;
> > +               }
> > +       }
> > +
> > +       return x86_acpi_os_ioremap(phys, size);
> > +}
> At least this, perhaps also what patch 5 adds, likely wants to be limited
> to the XEN_DOM0 case? Or else I wonder whether ...
>
> > @@ -850,6 +876,10 @@ void __init xen_add_remap_nonram(phys_addr_t maddr, 
> > phys_addr_t paddr,
> >                 BUG();
> >         }
> >   
> > +	/* Switch to the Xen acpi_os_ioremap() variant. */
> > +       if (nr_nonram_remap == 0)
> > +               acpi_os_ioremap = xen_acpi_os_ioremap;
> ... this would actually build when XEN_DOM0=n.
>
> I'm actually surprised there's no Dom0-only code section in this file,
> where the new code could then simply be inserted.
I'd rather make this conditional on CONFIG_ACPI.

Depending on how Xen tools will handle a PV-domain with "e820_host=1" this
code might be important for domUs, too.


Juergen

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