On Fri, 2 Sep 2011 09:54:31 -0500 Stephen Frazier <ste...@doc.state.ok.us> wrote:
> On 9/2/2011 7:37 AM, Martin Schwidefsky wrote: > > There is no documentation for z/VM as the edat facility is not > > supported. The emulation for large pages takes place in the Linux guest. > Looking at IBM past support for new hardware in guests of z/VM, I would > suggest that it will be supported in z/VM 7.1 or before. Look for edat > facility support to be added in a as yet unannounced point release of > z/VM 6.?. Also, IBM probably will not talk about it until they are ready > to announce it. This is harder than it looks. With z/VM you have two complete sets of page tables to worry about, the host page table and the guest page table. The host page table differs from the guest page table, each entry in the lowest level of the page table (the pte) has an extension (the pgste). Among other things you have the guest/host reference-backup-bit and the guest/host change-backup-bit in the pgste which are required to get paging right over the two levels of page tables. Now what happens if z/VM uses large pages in the host page table for the guest? The pgste table is tied to the pte table but that table does not exists if the segment table entry points to a 1MB frame. You loose access to the backup bits and your normal paging does not work anymore. The virtualization of the edat architecture is hard. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
