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[Xen-devel] EFI boot Issue with setup_xenheap_mappings()

Hi All,

After we resolved the flushing and tlbi issues previously discussed, I ran into a couple more issues. Please note that the available memory regions retrieved from EFI system table are:

(XEN) RAM: 0000008001000000 - 0000008007ffdfff <- (1)
(XEN) RAM: 0000008007ffe000 - 0000008007ffffff
(XEN) RAM: 0000008008000000 - 000000801fffdfff
(XEN) RAM: 000000801fffe000 - 000000801fffffff
(XEN) RAM: 0000008020000000 - 000000802fffffff
(XEN) RAM: 0000008030001000 - 00000083f0ffffff
(XEN) RAM: 00000083f1000000 - 00000083f101ffff
(XEN) RAM: 00000083f1020000 - 00000083fbbb1fff
(XEN) RAM: 00000083fc4b8000 - 00000083fc4b8fff
(XEN) RAM: 00000083fc6a4000 - 00000083fec25fff
(XEN) RAM: 00000083fec26000 - 00000083fee8bfff
(XEN) RAM: 00000083fee8c000 - 00000083ff225fff
(XEN) RAM: 00000083ff226000 - 00000083ff263fff
(XEN) RAM: 00000083ff265000 - 00000083ff2c4fff
(XEN) RAM: 00000083ffe70000 - 00000083ffffffff

(1) Physical memory actually started at 0x80_0000_0000, the first 16MB is used by UEFI.

Data abort is happening at:
    -> setup_mm()
      -> init_boot_pages()
        -> bootmem_region_add()
          -> Accessing bootmem_region_list causing data abort !!!

bootmem_region_list is initialized by "init_boot_pages()" at the first calling of "bootmem_region_add()". It points to VA 0x800000000000, which is at the beginning of the 1:1 mapping of RAM region (slots 256) (see include/asm-arm/config.h for complete ARM64 memory layout).

So, I looked at how the page table is setup for this region. This is done at the following place:
    -> setup_mm()
-> setup_xenheap_mappings(bank_start>>PAGE_SHIFT, bank_size>>PAGE_SHIFT)

Inside setup_xenheap_mapping():
  offset = pfn_to_pdx(base_mfn - xenheap_mfn_start).
      base_mfn          = 0x8000000
      xenheap_mfn_start = 0x8010000

This results in the math above to fail, and resulting in invalid offset, invalid vaddr, and invalid pte for this region.

So, I put a hack where I set base_mfn and xenheap_mfn_start to 0x8010000 in the code above (not sure if this is the right things to do), and this seems to resolve issue 1 continue all the way to setup_frame_table_mapping().

Here, it is also getting data abort when accessing frame_table (at 0x800000000 = 32GB). It seems that the page table for this region is also messed up.

Need a break and more investigation at this point.


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