From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver Date: Tue, 18 Dec 2018 03:40:08 +0200 Message-ID: <20181218014008.GD333@linux.intel.com> References: <20181217183613.GD12491@linux.intel.com> <20181217184333.GA26920@linux.intel.com> <20181217194913.GD29785@linux.intel.com> <16fdd37a-b9cc-1045-1497-2cfff6af176a@intel.com> <826f6a5a-fdf6-e7e5-d2d8-bcdc57c016fe@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andy Lutomirski Cc: Dave Hansen , Sean Christopherson , X86 ML , Platform Driver , linux-sgx@vger.kernel.org, nhorman@redhat.com, npmccallum@redhat.com, "Ayoun, Serge" , shay.katz-zamir@intel.com, Haitao Huang , Andy Shevchenko , Thomas Gleixner , "Svahn, Kai" , mark.shanahan@intel.com, Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Darren Hart , Andy Shevchenko , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" List-Id: platform-driver-x86.vger.kernel.org On Mon, Dec 17, 2018 at 12:10:17PM -0800, Andy Lutomirski wrote: > On Mon, Dec 17, 2018 at 12:03 PM Dave Hansen wrote: > > > > On 12/17/18 11:55 AM, Andy Lutomirski wrote: > > >> You're effectively rebuilding reverse-mapping infrastructure here. It's > > >> a frequent thing for the core VM to need to go from 'struct page' back > > >> to the page tables mapping it. For that we go (logically) > > >> page->{anon_vma,mapping}->vma->vm_mm->pagetable. > > > This is a bit outside my expertise here, but doesn't > > > unmap_mapping_range() do exactly what SGX wants? > > > > There's no 'struct page' for enclave memory as it stands. That means no > > page cache, and that means there's no 'struct address_space *mapping' in > > the first place. > > > > Basically, the choice was made a long time ago to have SGX's memory > > management live outside the core VM. I've waffled back and forth on it, > > but I do still think this is the right way to do it. > > AFAICS a lack of struct page isn't a problem. The core code seems to > understand that address_space objects might cover non-struct-page > memory. Morally, enclave memory is a lot like hot-unpluggable PCI > space. I'm fine using it if it works. Will try it for v19. /Jarkko