Hi Rob, On 21/11/13 14:28, Rob Herring wrote: > On Thu, Nov 21, 2013 at 2:59 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: >> PSCI is an ARM standard that provides a generic interface that >> supervisory software can use to manage power in the following >> situations: >> - Core idle management >> - CPU hotplug >> - big.LITTLE migration models >> - System shutdown and reset >> >> It basically allows the kernel to offload these tasks to the firmware, >> and rely on common kernel side code. >> >> More importantly, it gives a way to ensure that CPUs enter the kernel >> at the appropriate exception level (ie HYP mode, to allow the use of >> the virtualization extensions), even across events like CPUs being >> powered off/on or suspended. >> >> The main idea here is to reuse some of the existing u-boot code to >> create a separate blob that can live in SRAM (or a reserved page of >> memory), containing a secure monitor that will implement the PSCI >> operations. This code will still be alive when u-boot is long gone, >> hence the need for a piece of memory that will not be touched by the >> OS. > > Interesting. As a separate binary, I'm not sure this belongs or > benefits from being in u-boot. I would like to see this as a more > generic secure firmware loader or PSCI code be a part of u-boot code > directly. With the latter, you could extend it beyond PSCI to things > like env variable access (basically equivalent to UEFI runtime > services). I'm not saying we should do that though. So I started this by having something that was actually part of u-boot, and copying itself into SRAM, patching stuff as it went. The net result was that I was reinventing a runtime linker. Needless to say, I gave up quickly... ;-) What could be done would be for u-boot to be at least partially linked to run from some other region. That would allow for the secure mode services to be both part of u-boot, and stay resident. That'd probably be a good thing to have a look at. > BTW, you will need to mark this region reserved in the dtb if in system RAM. Yes. Eventually, I'd like the psci mode to be entirely generated from u-boot, as well as the eventual RAM reserved. M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
