Messages in this thread | | | Date | Thu, 21 Jun 2012 17:35:37 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] phys_efi_set_virtual_address_map needs va, no pa. |
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On 06/21/2012 09:52 AM, Robin Holt wrote: > > I am completely lost as to what should be done. How do we know > which identity maps need to be created? Do we just add them as we are > scanning the e820/EFI memory maps and include the reserved, etc ranges? > Do we look at the table handed to us by EFI at the beginning of boot and > use that as the basis? Or do we simply wait until the kernel's memory > initialization is complete and cover all of physical memory from zero > up to the highest physical address? >
Robin, we already create the 1:1 maps. Right now there is some weirdness with some of the issues that you mention, but that is orthogonal to this.
The 1:1 map created for the kernel is created at a specific offset, __PAGE_OFFSET, and is propagated into every vm context created by the kernel. There are two problems:
1. The "initial" (32 bit) or "trampoline" (64 bit) maps aren't on the list of vm contexts created by the kernel (pgd_list), so they never get updated after a particular point in the boot.
2. The initial/trampoline maps need these mappings not just at address __PAGE_OFFSET, but also at address zero (identity mapping), which means that just adding it to the pgd_list is insufficient.
Note that i386-PAE is unaffected, simply because the contents of the top (3rd) level is always fixed.
-hpa
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