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Sun, 04 Oct 2020 22:27:50 +0000 Date: Sun, 4 Oct 2020 23:27:50 +0100 From: Matthew Wilcox To: Jarkko Sakkinen Cc: x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Jethro Beekman , Haitao Huang , Chunyang Hui , Jordan Hand , Nathaniel McCallum , Seth Moore , Darren Kenny , Sean Christopherson , Suresh Siddha , andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com, mikko.ylinen@intel.com Subject: Re: [PATCH v39 11/24] x86/sgx: Add SGX enclave driver Message-ID: <20201004222750.GI20115@casper.infradead.org> References: <20201003045059.665934-1-jarkko.sakkinen@linux.intel.com> <20201003045059.665934-12-jarkko.sakkinen@linux.intel.com> <20201003195440.GD20115@casper.infradead.org> <20201004215049.GA43926@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201004215049.GA43926@linux.intel.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 05, 2020 at 12:50:49AM +0300, Jarkko Sakkinen wrote: > What is shoukd take is encl->lock. > > The loop was pre-v36 like: > > idx_start = PFN_DOWN(start); > idx_end = PFN_DOWN(end - 1); > > for (idx = idx_start; idx <= idx_end; ++idx) { > mutex_lock(&encl->lock); > page = radix_tree_lookup(&encl->page_tree, idx); > mutex_unlock(&encl->lock); > > if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) > return -EACCES; > } > > Looking at xarray.h and filemap.c, I'm thinking something along the > lines of: > > for (idx = idx_start; idx <= idx_end; ++idx) { > mutex_lock(&encl->lock); > page = xas_find(&xas, idx + 1); > mutex_unlock(&encl->lock); > > if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) > return -EACCES; > } > > Does this look about right? Not really ... int ret = 0; mutex_lock(&encl->lock); rcu_read_lock(); while (xas.index < idx_end) { page = xas_next(&xas); if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) ret = -EACCESS; break; } } rcu_read_unlock(); mutex_unlock(&encl->lock); return ret; ... or you could rework to use the xa_lock instead of encl->lock. I don't know how feasible that is for you.