On Fri, 2014-11-28 at 10:53 +0000, David Laight wrote: > From: Benjamin Herrenschmidt > > On Fri, 2014-11-28 at 08:45 +0530, Madhavan Srinivasan wrote: > > > > Can't we just unconditionally clear at as long as we do that after we've > > > > saved it ? In that case, it's just a matter for the fixup code to check > > > > the saved version rather than the actual CR.. > > > > > > > I use CR bit setting in the interrupt return path to enter the fixup > > > section search. If we unconditionally clear it, we will have to enter > > > the fixup section for every kernel return nip right? > > > > As I said above. Can't we look at the saved version ? > > > > IE. > > > > - On interrupt entry: > > > > * Save CR to CCR(r1) > > * clear CR5 > > > > - On exit > > > > * Check CCR(r1)'s CR5 field > > * restore CR > > Actually there is no real reason why the 'fixup' can't be done > during interrupt entry.
Other than if we crash, we get the wrong PC in the log etc... unlikely but I tend to prefer this. Also if we ever allow something like a local atomic on a faulting (uesrspace) address, we want a precise PC on entry. Generally, we have a lot more entry path than exit path, it's easier to keep the entry path simpler. Cheers, Ben. > David > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
