[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v3 6/7] xen: allow mapping ACPI data using a different physical address
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) > + * 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. Jan
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