RE: [PATCH 1/2] x86/efi: Unmap efi boot services code/data regions from efi_pgd

[Prakhya, Sai Praneeth]

> On 10/21/2018 06:57 PM, Ingo Molnar wrote:
> > Does the CPU _ever_ look look at the PFN if the page is
> > !_PAGE_PRESENT, for example speculatively? If yes then what is the
> > recommended value for the pfn - zero perhaps?
> 
> I'll never say never. :)
> 
> For L1TF[1], we know the CPU did exactly this; it ignored the _PAGE_PRESENT
> bit when fetching data from the L1.  That's what is worked around with the gunk
> in arch/x86/include/asm/pgtable-invert.h.
> 
> I think Andi plugged the code in here at a low enough level in the page table
> manipulation that pageattr.c should inherit it without doing anything explicit.
> But, Sai, you might want to double-check this.
> 
> 1.
> https://www.intel.com/content/www/us/en/architecture-and-
> technology/l1tf.html

Sure! Dave. Thanks for the link. I will take a look at it.

Regards,
Sai