From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Date: Mon, 17 Jun 2019 09:27:55 +0000 Subject: Re: [PATCH, RFC 18/62] x86/mm: Implement syncing per-KeyID direct mappings Message-Id: <20190617092755.GA3419@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <20190508144422.13171-1-kirill.shutemov@linux.intel.com> <20190508144422.13171-19-kirill.shutemov@linux.intel.com> <20190614095131.GY3436@hirez.programming.kicks-ass.net> <20190614224309.t4ce7lpx577qh2gu@box> In-Reply-To: <20190614224309.t4ce7lpx577qh2gu@box> To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Andrew Morton , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Andy Lutomirski , David Howells , Kees Cook , Dave Hansen , Kai Huang , Jacob Pan , Alison Schofield , linux-mm@kvack.org, kvm@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org On Sat, Jun 15, 2019 at 01:43:09AM +0300, Kirill A. Shutemov wrote: > On Fri, Jun 14, 2019 at 11:51:32AM +0200, Peter Zijlstra wrote: > > On Wed, May 08, 2019 at 05:43:38PM +0300, Kirill A. Shutemov wrote: > > > For MKTME we use per-KeyID direct mappings. This allows kernel to have > > > access to encrypted memory. > > > > > > sync_direct_mapping() sync per-KeyID direct mappings with a canonical > > > one -- KeyID-0. > > > > > > The function tracks changes in the canonical mapping: > > > - creating or removing chunks of the translation tree; > > > - changes in mapping flags (i.e. protection bits); > > > - splitting huge page mapping into a page table; > > > - replacing page table with a huge page mapping; > > > > > > The function need to be called on every change to the direct mapping: > > > hotplug, hotremove, changes in permissions bits, etc. > > > > And yet I don't see anything in pageattr.c. > > You're right. I've hooked up the sync in the wrong place. > > > > Also, this seems like an expensive scheme; if you know where the changes > > where, a more fine-grained update would be faster. > > Do we have any hot enough pageattr users that makes it crucial? > > I'll look into this anyway. The graphics people would be the most agressive users of this I'd think. They're the ones that yelled when I broke it last ;-)