Re: [PATCHv3 2/3] x86/tdx: Fix race between set_memory_encrypted() and load_unaligned_zeropad()

[Kirill A. Shutemov]

On Tue, Jun 06, 2023 at 11:14:29AM -0700, Dave Hansen wrote:
> On 6/6/23 02:56, Kirill A. Shutemov wrote:
> > load_unaligned_zeropad() can touch memory that is not owned by the
> > caller, but just happened to next after the owned memory.
> > This load_unaligned_zeropad() behaviour makes it important when kernel
> > asks VMM to convert a GPA from shared to private or back. Kernel must
> > never have a page mapped into direct mapping (and aliases) as private
> > when the GPA is already converted to shared or when GPA is not yet
> > converted to private.
> > 
> > load_unaligned_zeropad() can touch memory that is not owned by the
> > caller, but just happens to be next after the owned memory. This
> > load_unaligned_zeropad() behavior makes it important when the kernel
> > asks VMM to convert a GPA from shared to private or back. The kernel
> > must never have a page mapped into direct mapping (and aliases) as
> > private when the GPA is already converted to shared or when the GPA is
> > not yet converted to private.
> 
> Heh, that must be really important info to have it in the changelog twice!
> 
> I'll fix it up when I apply it.

Ouch. Please fix the comment in the code too.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov