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    SubjectRe: [PATCHv3 08/11] arm64: Check for selected granule support
    On Thu, Oct 15, 2015 at 09:47:53AM -0500, Jeremy Linton wrote:
    > On 10/15/2015 06:25 AM, Suzuki K. Poulose wrote:
    > >+ /*
    > >+ * Check to see if the CPU supports the requested pagesize
    > >+ */
    > >+ asm volatile("mrs %0, ID_AA64MMFR0_EL1" : "=r" (aa64mmfr0_el1));
    > >+ aa64mmfr0_el1 >>= ID_AA64MMFR0_TGRAN_SHIFT;
    > >+ if ((aa64mmfr0_el1 & 0xf) != ID_AA64MMFR0_TGRAN_SUPPORTED) {
    > >+ pr_efi_err(sys_table_arg, PAGE_SIZE_STR" granule not supported by the CPU\n");
    > >+ return EFI_UNSUPPORTED;
    > >+ }
    >
    >
    > This is definitely an improvement over my original hack job.
    >
    > I would like to add, that I actually think this should be in a new
    > function "check_kernel_compatibility" (or whatever) that is called
    > before handle_kernel_image.

    To bikeshed, perhaps efi_arch_check_system?

    > That is because I don't really think it belongs in
    > handle_kernel_image which is focused on relocation. Plus, if you add
    > another function, you can avoid the "Failed to relocate kernel"
    > error that comes out following the granule not supported message.
    > Further, checks like this in the future will have a place to live.

    I agree.

    There are some other diagnostic utilities I'd like to add to the stub
    (e.g. dumping the memory map and ID registers) that would help with
    diagnosing boot issues. I started on those at Connect, but realised I
    needed to first implement half of printf for those to be useful.

    > Of course you will then need a matching stubbed out function for the
    > normal arm kernel as well.

    I'm sure there are similar things we'll want to check for 32-bit (e.g.
    LPAE support), but a stub should be fine for now.

    Thanks,
    Mark.


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