Re: [PATCH] phys_efi_set_virtual_address_map needs va, no pa.

From: Matthew Garrett
Date: Wed Jun 20 2012 - 08:07:04 EST


On Wed, Jun 20, 2012 at 03:24:57AM -0500, Robin Holt wrote:
> The kernel allocated memmap may end up being beyond the first
> 512GB of memory. That early range is identity mapped, while the
> remainder of memory is not. The net result is the memmap allocated by
> efi_enter_virtual_mode will not be accessible via its __pa as is currently
> passed back to EFI.
>
> Since EFI is going to have to parse the passed in table, I believe the
> EFI documentation is wrong.
>
> I asked one of our BIOS engineers to look at the Intel reference code
> and he said it was obvious that the address would have to be a virtaully
> accessible address as we are in virtual mode while EFI is handling the
> callback.

No, that's completely wrong. UEFI can't be called in virtual mode until
*after* SetVirtualAddressMap(). The UEFI spec indicates that all
physical memory must have an identity mapping at this stage (section
2.3.4), so if we don't then that's a bug that needs to be fixed.

--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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