On Thu, Jun 02, 2016 at 03:52:46PM +0100, Matt Fleming wrote:
> On Tue, 31 May, at 04:14:31PM, Catalin Marinas wrote:
> > Since the EFI page size is 4KB, it is possible for a !4KB page kernel to
> > align an EFI runtime map boundaries in a way that they can overlap
> > within the same page. This requires the current create_pgd_mapping()
> > code to be able to split existing larger mappings when an overlapping
> > region needs to be mapped.
> >
> > With this patch, efi_create_mapping() scans the EFI memory map for
> > overlapping regions and trims the length of the current map to avoid a
> > large block mapping and subsequent split.
> >
> > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> > ---
> > arch/arm64/kernel/efi.c | 22 +++++++++++++++++++---
> > 1 file changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> > index 78f52488f9ff..0d5753c31c7f 100644
> > --- a/arch/arm64/kernel/efi.c
> > +++ b/arch/arm64/kernel/efi.c
> > @@ -62,10 +62,26 @@ struct screen_info screen_info __section(.data);
> > int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
> > {
> > pteval_t prot_val = create_mapping_protection(md);
> > + phys_addr_t length = md->num_pages << EFI_PAGE_SHIFT;
> > + efi_memory_desc_t *next = md;
> >
> > - create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
> > - md->num_pages << EFI_PAGE_SHIFT,
> > - __pgprot(prot_val | PTE_NG));
> > + /*
> > + * Search for the next EFI runtime map and check for any overlap with
> > + * the current map when aligned to PAGE_SIZE. In such case, defer
> > + * mapping the end of the current range until the next
> > + * efi_create_mapping() call.
> > + */
> > + for_each_efi_memory_desc_continue(next) {
> > + if (!(next->attribute & EFI_MEMORY_RUNTIME))
> > + continue;
> > + if (next->phys_addr < PAGE_ALIGN(md->phys_addr + length))
> > + length -= (md->phys_addr + length) & ~PAGE_MASK;
> > + break;
> > + }
> > +
> > + if (length)
> > + create_pgd_mapping(mm, md->phys_addr, md->virt_addr, length,
> > + __pgprot(prot_val | PTE_NG));
> > return 0;
> > }
> >
>
> Is this mapping in chunks scheme required because of the EFI
> Properties Table restriction whereby relative offsets between regions
> must be maintained?
>
> Because if that's not the reason, I'm wondering why you can't simply
> update efi_get_virtmap() to align the virtual addresses to 64K?
Ard to confirm but I think the reason is the relative offset between
code and data regions that must be preserved. For example, on Juno I
get:
[ 0.000000] efi: 0x0009fff6e000-0x0009fffaefff [Runtime Code |RUN| | | | | | | |WB|WT|WC|UC]*
[ 0.000000] efi: 0x0009fffaf000-0x0009ffffefff [Runtime Data |RUN| | | | | | | |WB|WT|WC|UC]*
Since the code may assume relative loads from the data section, we need
to preserve this offset (which doesn't seem 64KB aligned).
--
Catalin
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