> On 13 Jan 2023, at 10:11, Julien Grall <jul...@xen.org> wrote: > > From: Julien Grall <jgr...@amazon.com> > > At the moment, switch_ttbr() is switching the TTBR whilst the MMU is > still on. > > Switching TTBR is like replacing existing mappings with new ones. So > we need to follow the break-before-make sequence. > > In this case, it means the MMU needs to be switched off while the > TTBR is updated. In order to disable the MMU, we need to first > jump to an identity mapping. > > Rename switch_ttbr() to switch_ttbr_id() and create an helper on > top to temporary map the identity mapping and call switch_ttbr() > via the identity address. > > switch_ttbr_id() is now reworked to temporarily turn off the MMU > before updating the TTBR. > > We also need to make sure the helper switch_ttbr() is part of the > identity mapping. So move _end_boot past it. > > The arm32 code will use a different approach. So this issue is for now > only resolved on arm64. > > Signed-off-by: Julien Grall <jgr...@amazon.com>
The sequence looks ok to me, also the reasoning about barriers and register dependencies discussed in the previous version. Reviewed-by: Luca Fancellu <luca.fance...@arm.com> I’ve also built for arm32/64 and test this patch on fvp, booting Dom0 and creating/running/destroying some guests Tested-by: Luca Fancellu <luca.fance...@arm.com>
