On 24/08/18 20:43, Jason Andryuk wrote: > On Wed, Aug 15, 2018 at 10:39 AM Juergen Gross <jgr...@suse.com> wrote: >> >> On 15/08/18 16:10, Jan Beulich wrote: >>>>>> On 15.08.18 at 15:17, <andrew.coop...@citrix.com> wrote: >>>> 2) 32bit PV guests which use writeable pagetable support will >>>> automatically get shadowed when the clear the lower half. >>> >>> ... of a page table entry. >>> >>>> Ideally, such >>>> guests should be modified to use hypercalls rather than the ptwr >>>> infrastructure (as its more efficient to begin with), but we can >>>> probably work around this in Xen by emulating the next few instructions >>>> until we have a complete PTE (same as the shadow code). >>> >>> Provided the intervening insns are simple enough. I've looked into >>> current Linux pv-ops code the other day, and afaict it's already >>> using mmu-op or cmpxchg8b, but not two separate mov-s. But >>> of course I've looked at the general routines only, not at things >>> perhaps hidden in special cases, or in init-only code. >> >> Look at xen_pte_clear(). Inside irq handling it will use (PAE case): >> >> static inline void native_pte_clear(struct mm_struct *mm, unsigned long >> addr, >> pte_t *ptep) >> { >> ptep->pte_low = 0; >> smp_wmb(); >> ptep->pte_high = 0; >> } > > I've been testing out set_64bit for PTE operations on 32bit PAE. I > haven't found all the spots, but shadowing is now enabled a few > seconds into boot instead of immediately. > > And yes, I think https://bugzilla.kernel.org/show_bug.cgi?id=198497 is > related as you presumed a while back.
I have a patch series (two patches) avoiding shadowing completely: https://lists.xen.org/archives/html/xen-devel/2018-08/msg01785.html Juergen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel