Re: [PATCH v5 05/10] x86, efi: Add efi_fake_mem support for EFI_MEMORY_SP
From: Dan Williams
Date: Fri Sep 13 2019 - 11:02:42 EST
On Fri, Sep 13, 2019 at 6:02 AM Ard Biesheuvel
> On Fri, 30 Aug 2019 at 03:07, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> > Given that EFI_MEMORY_SP is platform BIOS policy descision for marking
> > memory ranges as "reserved for a specific purpose" there will inevitably
> > be scenarios where the BIOS omits the attribute in situations where it
> > is desired. Unlike other attributes if the OS wants to reserve this
> > memory from the kernel the reservation needs to happen early in init. So
> > early, in fact, that it needs to happen before e820__memblock_setup()
> > which is a pre-requisite for efi_fake_memmap() that wants to allocate
> > memory for the updated table.
> > Introduce an x86 specific efi_fake_memmap_early() that can search for
> > attempts to set EFI_MEMORY_SP via efi_fake_mem and update the e820 table
> > accordingly.
> Is this early enough? The EFI stub runs before this, and allocates
> memory as well.
Unless I'm missing something the stub only allocates where the kernel
will land. That should be handled by the new mem_avoid_memmap()
extensions to consider "efi_fake_mem" in its exclusions.