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

[Jan Beulich <jbeulich@xxxxxxxx>]

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)?

> +     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.

Jan