On 10.09.24 14:34, Jan Beulich wrote:
On 10.09.2024 12:39, Juergen Gross wrote:When running as a Xen PV dom0 the system needs to map ACPI data of the host using host physical addresses, while those addresses can conflict with the guest physical addresses of the loaded linux kernel. The same problem might apply in case a PV guest is configured to use the host memory map. This conflict can be solved by mapping the ACPI data to a different guest physical address, but mapping the data via acpi_os_ioremap() must still be possible using the host physical address, as this address might be generated by AML when referencing some of the ACPI data. When configured to support running as a Xen PV domain, have an implementation of acpi_os_ioremap() being aware of the possibility to need above mentioned translation of a host physical address to the guest physical address. This modification requires to fix some #include of asm/acpi.h in x86 code to use linux/acpi.h instead. Signed-off-by: Juergen Gross <jgross@xxxxxxxx>Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> with a request to comment a tiny bit more:@@ -836,6 +837,33 @@ void __init xen_do_remap_nonram(void) pr_info("Remapped %u non-RAM page(s)\n", remapped); }+#ifdef CONFIG_ACPI+/* + * Xen variant of acpi_os_ioremap() taking potentially remapped non-RAM + * regions into acount.(Nit: account)
Indeed.
+ * 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; + const struct nonram_remap *remap = xen_nonram_remap; + + 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;This might be slightly easier / more logical to read as phys += remap->paddr - remap->maddr; Also because of "phys" not consistently expressing a physical address (when you need convert it, the incoming value is a machine address) a comment may help here. In fact at the first glance (and despite having seen the code before) I thought the translation was done the wrong way round, simply because of the name of the variable.
Will add a comment and change the line as you suggest. Juergen
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