Re: [PATCH] x86/mm: Decouple dynamic __PHYSICAL_MASK from AMD SME

[Kirill A. Shutemov]

On Tue, Feb 13, 2018 at 10:10:22PM -0600, Tom Lendacky wrote:
> On 2/8/2018 6:55 AM, Kirill A. Shutemov wrote:
> > AMD SME claims one bit from physical address to indicate whether the
> > page is encrypted or not. To achieve that we clear out the bit from
> > __PHYSICAL_MASK.
> 
> I was actually working on a suggestion by Linus to use one of the software
> page table bits to indicate encryption and translate that to the hardware
> bit when writing the actual page table entry.  With that, __PHYSICAL_MASK
> would go back to its original definition.

But you would need to mask it on reading of pfn from page table entry,
right? I expect it to have more overhead than this one.

And software bits are valuable. Do we still have a spare one for this?

-- 
 Kirill A. Shutemov