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. thanks -- PMM
