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

From: Juergen Gross
Date: Tue Sep 10 2024 - 04:17:24 EST

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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