On Fri, 2016-01-29 at 15:06 +0100, Ard Biesheuvel wrote: > On 29 January 2016 at 15:00, Mark Salter <msalter@xxxxxxxxxx> wrote: > > Hi Ard, > > > > I ran into an issue with your MEMBLOCK_NOMAP changes on a particular > > firmware. The symptom is the kernel panics at boot time when it hits > > an unmapped page while unpacking the initramfs. As it turns out, the > > start of the initramfs shares a 64k kernel page with the UEFI memmap. > > I can avoid the problem with: > > > > @@ -203,7 +203,7 @@ void __init efi_init(void) > > > > reserve_regions(); > > early_memunmap(memmap.map, params.mmap_size); > > - memblock_mark_nomap(params.mmap & PAGE_MASK, > > - PAGE_ALIGN(params.mmap_size + > > - (params.mmap & ~PAGE_MASK))); > > + memblock_reserve(params.mmap & PAGE_MASK, > > + PAGE_ALIGN(params.mmap_size + > > + (params.mmap & ~PAGE_MASK))); > > } > > > > > > But it makes me worry about the same potential problem with > > other reserved regions which we nomap. What do you think? > > > > So I take it this initramfs allocation is not made by the stub but by > GRUB? Since the stub rounds all allocations to 64 KB ... > Yes. GRUB. > In any case, regardless of the underlying cause, if any part of the > initramfs turns out not to be covered by the linear mapping, we should > invoke your code to move it. So I think it should be a matter of > refining the logic in relocate_initrd() to do the right thing in this > case That thought had crossed my mind. I think it would be easy enough to trigger the copy if first or last page of initrd is unmapped. Somewhat related to this is that I want to rework this old patch to deal with acpi tables outside mapped ram: https://lkml.org/lkml/2015/5/14/357 Basically, we should be able to just do: diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h index 15e0aad..4ea638c 100644 --- a/arch/arm64/include/asm/acpi.h +++ b/arch/arm64/include/asm/acpi.h @@ -32,7 +32,7 @@ static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size) { - if (!page_is_ram(phys >> PAGE_SHIFT)) + if (!memblock_is_memory(phys)) return ioremap(phys, size); return ioremap_cache(phys, size); But this doesn't currently work wrt mem= which works by removing the end range of memblocks. If I have mem= use the nomap flag rather than removing the range, the above acpi_os_ioremap change works, but other issues crop up due to memblock_end_of_DRAM() returning end of all DRAM regardless of mem=. So we end up with PFNs and struct pages for memory which will never be in linear map. Fixing memblock_end_of_DRAM() to look at the flags and return end of mapped DRAM gets things working but I wonder about other potential trouble spots with this approach. Any thoughts? > > Your suggested change will break 32-bit ARM, since we use > ioremap_nocache() to map the UEFI memory map, and ARM does not allow > that on ranges that are part of the linear mapping. okay. I'll put together a patch to the initrd relocating code. Thanks! -- 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
