On Tue, 2014-11-11 at 10:42 -0500, Mark Salter wrote: > On Mon, 2014-11-10 at 08:31 +0100, Ard Biesheuvel wrote: > > On 10 November 2014 05:11, Mark Salter <msalter@xxxxxxxxxx> wrote: > > > On Thu, 2014-11-06 at 15:13 +0100, Ard Biesheuvel wrote: > > >> This changes the way memblocks are installed based on the contents > > of > > >> the UEFI memory map. Formerly, all regions would be > > memblock_add()'ed, > > >> after which unusable regions would be memblock_reserve()'d as well. > > >> To simplify things, but also to allow access to the unusable > > regions > > >> through mmap(/dev/mem), even with CONFIG_STRICT_DEVMEM set, change > > >> this so that only usable regions are memblock_add()'ed in the first > > >> place. > > > > > > This patch is crashing 64K pagesize kernels during boot. I'm not > > exactly > > > sure why, though. Here is what I get on an APM Mustang box: > > > > > > > Ah, yes, I meant to mention this patch > > > > https://git.kernel.org/cgit/linux/kernel/git/glikely/linux.git/commit/?id=8cccffc52694938fc88f3d90bc7fed8460e27191 > > > > in the cover letter, which addresses this issue at least for the DT > > case. > > > > That isn't the problem. In general, with 64K kernel pages, you can't be > sure if you leave something you need out of the kernel linear mapping. > If you have Loader Code/Data regions begin and/or end at something other > than a 64K boundary and that region is adjacent to a region not being > added, then you end up leaving out the unaligned bits from the linear > mapping. This could be bits of the initramfs or devicetree. > > What I don't get with this failure is that it is an alignment fault > which should be masked at EL1 for the kernel. The same unaligned > access happens without this patch and it doesn't generate a fault. > Ah, but unaligned accesses are not ignored for device memory. I have this in include/acpi/acpi_io.h: static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size) { #ifdef CONFIG_ARM64 if (!page_is_ram(phys >> PAGE_SHIFT)) return ioremap(phys, size); #endif return ioremap_cache(phys, size); } Because the table isn't in the linear mapping, it fails the page_is_ram() test and it gits mapped with ioremap() leading to the alignment fault. If I take out the code inside the #ifdef, I get a different fault: [ 0.350057] Unhandled fault: synchronous external abort (0x96000010) at 0xfffffe0000fae6f4 [ 0.358704] pgd = fffffe0001160000 [ 0.362276] [fffffe0000fae6f4] *pgd=0000004001370003, *pud=0000004001370003, *pmd=0000004001370003, *pte=02c00040011a0713 [ 0.373746] Internal error: : 96000010 [#1] SMP [ 0.378484] Modules linked in: [ 0.381601] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 3.18.0-rc4+ #15 [ 0.388248] Hardware name: APM X-Gene Mustang board (DT) [ 0.393738] task: fffffe03dbe10000 ti: fffffe03dbf00000 task.ti: fffffe03dbf00000 [ 0.401503] PC is at acpi_ex_system_memory_space_handler+0x238/0x2e0 [ 0.408160] LR is at acpi_ex_system_memory_space_handler+0x130/0x2e0 That happens because AML is trying to access a hardware register which has been mapped as normal memory. So, we need a way to tell a table in ram from an io address in AML. And page_is_ram() no longer cuts it if the tables are not in the linear mapping. -- 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
