On 23/02/21(Tue) 00:24, Mark Kettenis wrote:
> > Date: Mon, 22 Feb 2021 10:10:21 +0100
> > From: Martin Pieuchot <m...@openbsd.org>
> >
> > On 16/02/21(Tue) 11:20, Martin Pieuchot wrote:
> > > Start by moving `pgo_fault' handler outside of uvm_fault_lower().
> > >
> > > If a page has a backing object that prefer to handler to fault itself
> > > the locking will be different, so keep it under KERNEL_LOCK() for the
> > > moment and make it separate from the rest of uvm_fault_lower().
> > >
> > > ok?
> >
> > Anyone?
>
> This diverges from NetBSD; you think that's a good idea?
Which tree are you looking at? I'm doing this exactly to reduce
differences with NetBSD. r1.228 of uvm_fault.c in NetBSD contain this
logic in uvm_fault_internal().
> > > Index: uvm/uvm_fault.c
> > > ===================================================================
> > > RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
> > > retrieving revision 1.115
> > > diff -u -p -r1.115 uvm_fault.c
> > > --- uvm/uvm_fault.c 16 Feb 2021 09:10:17 -0000 1.115
> > > +++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -0000
> > > @@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
> > > /* case 1: fault on an anon in our amap */
> > > error = uvm_fault_upper(&ufi, &flt, anons, fault_type);
> > > } else {
> > > - /* case 2: fault on backing object or zero fill */
> > > - KERNEL_LOCK();
> > > - error = uvm_fault_lower(&ufi, &flt, pages, fault_type);
> > > - KERNEL_UNLOCK();
> > > + struct uvm_object *uobj = ufi.entry->object.uvm_obj;
> > > +
> > > + /*
> > > + * if the desired page is not shadowed by the amap and
> > > + * we have a backing object, then we check to see if
> > > + * the backing object would prefer to handle the fault
> > > + * itself (rather than letting us do it with the usual
> > > + * pgo_get hook). the backing object signals this by
> > > + * providing a pgo_fault routine.
> > > + */
> > > + if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > > + KERNEL_LOCK();
> > > + error = uobj->pgops->pgo_fault(&ufi,
> > > + flt.startva, pages, flt.npages,
> > > + flt.centeridx, fault_type, flt.access_type,
> > > + PGO_LOCKED);
> > > + KERNEL_UNLOCK();
> > > +
> > > + if (error == VM_PAGER_OK)
> > > + error = 0;
> > > + else if (error == VM_PAGER_REFAULT)
> > > + error = ERESTART;
> > > + else
> > > + error = EACCES;
> > > + } else {
> > > + /* case 2: fault on backing obj or zero fill */
> > > + KERNEL_LOCK();
> > > + error = uvm_fault_lower(&ufi, &flt, pages,
> > > + fault_type);
> > > + KERNEL_UNLOCK();
> > > + }
> > > }
> > > }
> > >
> > > @@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
> > > struct vm_anon *anon = NULL;
> > > vaddr_t currva;
> > > voff_t uoff;
> > > -
> > > - /*
> > > - * if the desired page is not shadowed by the amap and we have a
> > > - * backing object, then we check to see if the backing object would
> > > - * prefer to handle the fault itself (rather than letting us do it
> > > - * with the usual pgo_get hook). the backing object signals this by
> > > - * providing a pgo_fault routine.
> > > - */
> > > - if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > > - result = uobj->pgops->pgo_fault(ufi, flt->startva, pages,
> > > - flt->npages, flt->centeridx, fault_type, flt->access_type,
> > > - PGO_LOCKED);
> > > -
> > > - if (result == VM_PAGER_OK)
> > > - return (0); /* pgo_fault did pmap enter */
> > > - else if (result == VM_PAGER_REFAULT)
> > > - return ERESTART; /* try again! */
> > > - else
> > > - return (EACCES);
> > > - }
> > >
> > > /*
> > > * now, if the desired page is not shadowed by the amap and we have
> > >
> >
> >
