Re: [Qemu-arm] [Qemu-devel] [PATCH] target/arm: Allow to switch from MON->HYP on AArch32

[Alexander Graf]

On 01/09/2019 05:59 PM, Peter Maydell wrote:
> On Wed, 9 Jan 2019 at 16:52, Peter Maydell <address@hidden> wrote:
> > On Wed, 9 Jan 2019 at 15:26, Alexander Graf <address@hidden> wrote:
> > > In U-boot, we switch from S-SVC -> MON -> HYP when we want to enter
> > > HYP mode. This dance seems to work ok (hence it's there in the code
> > > base), but breaks with current QEMU.
> PS: it would be helpful if the commit message said how u-boot
> is trying to go from Mon to Hyp -- some ways to try to do
> this are OK, and some are not, so whether it's supposed to
> work or not depends on what u-boot is actually doing...

I don't fully understand all of it to be honest :). But the code is here:

http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/cpu/armv7/nonsec_virt.S

What I managed to understand so far is that it goes to MON using the smc 
#0 call and then changes SPSR so that on return (movs pc) the mode will 
be different.

But please double check whether this is supposed to work - I don't find 
mode switching on ARM terribly intuitive ;).


Alex