Messages in this thread | | | Date | Sat, 13 Apr 2024 00:23:33 +0300 | From | "" <> | Subject | Re: [PATCH] x86/tdx: Preserve shared bit on mprotect() |
| |
On Fri, Apr 12, 2024 at 08:48:56PM +0000, Edgecombe, Rick P wrote: > On Fri, 2024-04-12 at 22:12 +0300, Kirill A. Shutemov wrote: > > The TDX guest platform takes one bit from the physical address to > > indicate if the page is shared (accessible by VMM). This bit is not part > > of the physical_mask and is not preserved during mprotect(). As a > > result, the 'shared' bit is lost during mprotect() on shared mappings. > > > > _COMMON_PAGE_CHG_MASK specifies which PTE bits need to be preserved > > during modification. AMD includes 'sme_me_mask' in the define to > > preserve the 'encrypt' bit. > > > > To cover both Intel and AMD cases, include 'cc_mask' in > > _COMMON_PAGE_CHG_MASK instead of 'sme_me_mask'. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > Fixes: 41394e33f3a0 ("x86/tdx: Extend the confidential computing API to > > support TDX guests") > > Cc: Tom Lendacky <thomas.lendacky@amd.com> > > Cc: Chris Oo <cho@microsoft.com> > > Cc: Dexuan Cui <decui@microsoft.com> > > Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com> > > So does this mean there is shared memory mapped to userspace? Or is this a > theoretical correctness thing?
Drivers can do this. Things like VFIO, I guess.
I think I should have credited Chris for reporting and testing the problem:
Reported-and-tested-by: Chris Oo <cho@microsoft.com>
-- Kiryl Shutsemau / Kirill A. Shutemov
| |