On Thu, 2013-11-21 at 15:04 +0000, Marc Zyngier wrote: > 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. Can't you just build and link it as you do now and then link it into the .rodata section of the final u-boot image as a blob to copy out to the defined address at runtime? > 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. Did you mean "psci node" here? In which case yes please. Ian. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
