From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Date: Thu, 30 Jul 2015 09:43:44 -0600 Subject: [U-Boot] [PATCH] ARM: tegra: restrict usable RAM size further In-Reply-To: <20150730110455.GC10103@ulmo.nvidia.com> References: <1438199278-29247-1-git-send-email-swarren@wwwdotorg.org> <20150730110455.GC10103@ulmo.nvidia.com> Message-ID: <55BA4630.60506@wwwdotorg.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 07/30/2015 05:04 AM, Thierry Reding wrote: > On Wed, Jul 29, 2015 at 01:47:58PM -0600, Stephen Warren wrote: >> From: Stephen Warren >> >> Additionally, ARM64 devices typically run a secure monitor in EL3 and >> U-Boot in EL2, and set up some secure RAM carve-outs to contain the EL3 >> code and data. These carve-outs are located at the top of 32-bit address >> space. Restrict U-Boot's RAM usage to well below the location of those >> carve-outs. Ideally, we would the secure monitor would inform U-Boot of >> exactly which RAM it could use at run-time. However, I'm not sure how to >> do that at present (and even if such a mechanism does exist, it would >> likely not be generic across all forms of secure monitor). > > 0xe0000000-0xffffffff is 512 MiB, surely a secure monitor can live with > less than that! I'm sure it does. However, it's a nice round number and leaves plenty of space for arbitrary expansion of the secure monitor, secure OS, other security-related carve-outs, (video regions, LP0 resume firmware, etc.) There's still plenty of space left for U-Boot after that.