On 5/16/20 5:58 AM, Peter Maydell wrote: > On Sat, 16 May 2020 at 05:12, Richard Henderson > <richard.hender...@linaro.org> wrote: >> >> On 5/15/20 2:25 PM, Peter Maydell wrote: >>>> You also need to call arm_rebuild_hflags() after modifying CPSR_E >>>> otherwise the change doesn't take effect. >>> >>> Hmm. I was expecting cpsr_write() to take care of that if we >>> updated a cpsr flag that was in the hflags, but it looks like >>> the rebuild_hflags() is in the HELPER() wrapper but not in >>> cpsr_write() itself. Richard, does anything go wrong if >>> cpsr_write() proper does the hflags rebuild ? >> >> We wind up rebuilding hflags multiple times, is all. >> >> Most of the time we call cpsr_write we also do something else that also >> requires a rebuild. So we do it once after all updates. > > The downside is that it leaves a trap which makes it really > easy to introduce bugs where hflags aren't rebuilt: as > a caller of cpsr_write() I don't really want to have to > care which cpsr flags happen to be in the hflags or not, > and it's particularly awkward that simply fixing which > flags belong in CPSR_USER suddenly means that a call > that happened to be OK before is now buggy.
I don't see any way around that. As I said, if we put the rebuild in cpsr_write, then we should also rearrange the code that calls cpsr_write to assume that's where the rebuild gets done. r~
