On 24.11.16 13:44:31, Ard Biesheuvel wrote: > On 24 November 2016 at 13:42, Robert Richter <robert.richter@xxxxxxxxxx> wrote: > > On 23.11.16 21:25:06, Ard Biesheuvel wrote: > >> Why? MEMREMAP_WB is used often, among other things for mapping > >> firmware tables, which are marked as NOMAP, so in these cases, the > >> linear address is not mapped. > > > > If fw tables are mapped wb, that is wrong and needs a separate fix. > > > > Why is that wrong? The whole issue with mapping acpi tables is not marking them cachable, what wb does. Otherwise we could just use linear mapping for those mem ranges. > >> > If you think pfn_valid() is wrong here, I am happy to send a patch > >> > that fixes this by using page_is_ram(). In any case, the worst case > >> > that may happen is to behave the same as v4.4, we might fix then the > >> > wrong use of pfn_valid() where it is not correctly used to check for > >> > ram. > >> > > >> > >> page_is_ram() uses string comparisons to look for regions called > >> 'System RAM'. Is that something we can tolerate for each pfn_valid() > >> calll? > >> > >> Perhaps the solution is to reimplement page_is_ram() for arm64 using > >> memblock_is_memory() instead, But that still means we need to modify > >> the generic memremap() code first to switch to it before changing the > >> arm64 implementation of pfn_valid > > > > No, that's not the solution. pfn_valid() should just check if there is > > a valid struct page, as other archs do. And if there is a mis-use of > > pfn_valid() to check for ram, only that calls should be fixed to use > > page_is_ram(), however this is implemented, or something appropriate. > > But I don't see any problematic code, and if so, I will fix that. > > > > memremap() uses pfn_valid() to decide whether some address is covered > by the linear mapping. If we correct pfn_valid() to adhere to your > definition, we will need to fix memremap() first in any case. As said, will fix that if needed. But I think the caller is wrong then. -Robert -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
