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 15:18:53 +0200 Message-ID: <20181218131853.GC25667@linux.intel.com> References: <20181116010412.23967-19-jarkko.sakkinen@linux.intel.com> <7d5cde02-4649-546b-0f03-2d6414bb80b5@intel.com> <20181217180102.GA12560@linux.intel.com> <20181217183613.GD12491@linux.intel.com> <20181217184333.GA26920@linux.intel.com> <20181217222047.GG12491@linux.intel.com> <20181218013918.GC333@linux.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: Sean Christopherson , Dave Hansen , 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, Suresh Siddha , 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 08:55:02PM -0800, Andy Lutomirski wrote: > On Mon, Dec 17, 2018 at 5:39 PM Jarkko Sakkinen > wrote: > > > > On Mon, Dec 17, 2018 at 02:20:48PM -0800, Sean Christopherson wrote: > > > The only potential hiccup I can see is the build flow. Currently, > > > EADD+EEXTEND is done via a work queue to avoid major performance issues > > > (10x regression) when userspace is building multiple enclaves in parallel > > > using goroutines to wrap Cgo (the issue might apply to any M:N scheduler, > > > but I've only confirmed the Golang case). The issue is that allocating > > > an EPC page acts like a blocking syscall when the EPC is under pressure, > > > i.e. an EPC page isn't immediately available. This causes Go's scheduler > > > to thrash and tank performance[1]. > > > > I don't see any major issues having that kthread. All the code that > > maps the enclave would be removed. > > > > I would only allow to map enclave to process address space after the > > enclave has been initialized i.e. SGX_IOC_ENCLAVE_ATTACH. > > > > What's SGX_IOC_ENCLAVE_ATTACH? Why would it be needed at all? I > would imagine that all pages would be faulted in as needed (or > prefaulted as an optimization) and the enclave would just work in any > process. The way I see it the efficient way to implement this is to have the enclave attached to a single process address space at a time. #PF handler is trivial with multiple address spaces but swapping is a bit tedious as you would need to zap N processes. /Jarkko