On Thu, 2006-09-14 at 02:23 -0700, Zachary Amsden wrote: > Martin Schwidefsky wrote > > The discard fault happens on access to a volatile that has been > > discarded. An important property of the s390 architecture comes into > > play here: there are two page tables, a guest page table and a host page > > table. What the guest perceives as its "physical" memory is in virtual > > storage for the host. An address resolution has to walk two pages > > tables, if a pte is invalid in either table you get a fault. A guest > > fault if the invalid pte is in the guest table and a host fault if it is > > > > Yes, I'm familiar with that trick. Wasn't sure if you had it in > hardware or not. The mainframes have that trick in hardware for about 30 years .. > > in the host table. That gives s390 a simple method to implement > > discarded pages: the hypervisor just unmaps the page from the host table > > and changes the state of the guest page. I can see that you will have a > > much harder time to implement this on i386. > > > > Nah, I think we'll do just fine. I wonder which trick you use, since there is only one page table one i386 I can only imagine that you are tracking all page tables of the guest. > Thanks for the info - based on this, I think we can probably use the > volatile page / swap cache changes as well for VMware, also pretty much > unchanged. Sorry to take so long to look at these patches, BTW - I was > on holiday for two weeks. I've been sitting on these patches for months now and you are worrying about two weeks.. -- blue skies, Martin. Martin Schwidefsky Linux for zSeries Development & Services IBM Deutschland Entwicklung GmbH "Reality continues to ruin my life." - Calvin.
