On Fri, 2012-09-07 at 09:51 +0100, Jan Beulich wrote: > >>> On 07.09.12 at 10:46, Huang Ying <ying.huang@xxxxxxxxx> wrote: > > On Fri, 2012-09-07 at 08:12 +0100, Jan Beulich wrote: > >> >>> On 07.09.12 at 09:02, Huang Ying <ying.huang@xxxxxxxxx> wrote: > >> > On Fri, 2012-09-07 at 07:40 +0100, Jan Beulich wrote: > >> >> At least for Xen Dom0 it is very relevant to set the _PAGE_IO bit when > >> >> ioremap-ing (non-RAM) areas, as that flag suppresses the PFN -> MFN > >> >> translation otherwise done in PV guests. (The offending commit was > >> >> 81e88fdc432a1552401d6e91a984dcccce72b8dc.) > >> > > >> > If my understanding were correct, ghes_ioremap_pfn_nmi normally only map > >> > RAM. > >> > >> But not RAM in the sense of what is seen as usable memory in the > >> E820 map. What you're mapping here is reserved memory, and that > >> is (from the perspective of the kernel and Xen) non-RAM. The fact > >> that it is RAM from a machine perspective is manifested by the > >> mapping not needing to be done UC or alike. > > > > I think the key is to keep these memory range map consistent between > > each other. BIOS may map these memory cached. ACPI may mapped them as > > cached (see acpi_os_ioremap) too. > > But that aspect is orthogonal to the patch here - all we need > done for Xen is the proper setting of _PAGE_IO; cachability > is being dealt with independently (and correctly I think). Sorry, don't know much about Xen. Just think we should keep mapping consistent about whether cached in native environment. Best Regards, Huang Ying -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
