On Tue, May 10, 2016 at 09:09:55AM +0100, Peter Maydell wrote: > On 10 May 2016 at 01:16, Alistair Francis <alistair.fran...@xilinx.com> wrote: > > It is actually a u-boot problem. I originally just assumed it was a > > Linux problem, but it happens before u-boot hands off to Linux. > > OK, that makes sense. u-boot tends to be a bit lower level and less > hardware-agnostic. I just wanted to check it wasn't caused by some > problem in QEMU's EL3 support we could easily fix. > > > It appears that u-boot won't work at all with EL3 enabled but EL2 > > disabled. It always moves to EL2 before moving to EL1 and there is no > > code prepared to handle going from EL3 directly to EL1. > > > > Just for the record, I'm specifically talking about what happens in > > the do_nonsec_virt_switch() function. > > > > It looks like there are three options: > > 1. Add support to u-boot to drop from EL3 to EL1 (I'm assuming this > > is possible, as not all implementations have EL2) > > 2. Just wait until QEMU adds EL2 support > > 3. Allow a QEMU command line option to start in EL1 instead of EL3
Alistair, Our usual ZynqMP boot flow is ATF at EL3 ATF hands over to u-boot at EL2 u-boot hands over to the Linux kernel at EL2 Our ATF has a mode where it can be instructed to start u-boot in EL1, bypassing EL2. That would avoid this issue. You don't need to recompile ATF. We can discuss the details off-line. > I would be OK with any of these three from a QEMU perspective. > Fixing u-boot is probably conceptually the nicest but I've never > looked at u-boot internals so it could be simple or painful... > > Edgar, do you have the list of what we're still missing before we > can turn on EL2? We're missing the Data Abort ISS:s, we're missing modelling of a few registers (like HSTR_EL2). Some regs are quite incomplete like HCR but I think we can live with that. GICv2 virtualization is missing. We are also missing a few AT_ modes. AArch32 support is probably lacking alot of more stuff. IIRC, last time this came up we talked about enabling EL2 after ISS and GICv2 virtualization support gets merged + a few odd regs. Enough to allow Xen and KVM to work under emulation. Cheers, Edgar
