On 25.04.2022 10:29, Jan Beulich wrote: > For a long time we've been rather inefficient with IOMMU page table > management when not sharing page tables, i.e. in particular for PV (and > further specifically also for PV Dom0) and AMD (where nowadays we never > share page tables). While up to about 2.5 years ago AMD code had logic > to un-shatter page mappings, that logic was ripped out for being buggy > (XSA-275 plus follow-on). > > This series enables use of large pages in AMD and Intel (VT-d) code; > Arm is presently not in need of any enabling as pagetables are always > shared there. It also augments PV Dom0 creation with suitable explicit > IOMMU mapping calls to facilitate use of large pages there. Depending > on the amount of memory handed to Dom0 this improves booting time > (latency until Dom0 actually starts) quite a bit; subsequent shattering > of some of the large pages may of course consume some of the saved time. > > Known fallout has been spelled out here: > https://lists.xen.org/archives/html/xen-devel/2021-08/msg00781.html > > There's a dependency on 'PCI: replace "secondary" flavors of > PCI_{DEVFN,BDF,SBDF}()', in particular by patch 8. Its prereq patch > still lacks an Arm ack, so it couldn't go in yet. > > I'm inclined to say "of course" there are also a few seemingly unrelated > changes included here, which I just came to consider necessary or at > least desirable (in part for having been in need of adjustment for a > long time) along the way. Some of these changes are likely independent > of the bulk of the work here, and hence may be fine to go in ahead of > earlier patches. > > See individual patches for details on the v4 changes. > > 01: AMD/IOMMU: correct potentially-UB shifts > 02: IOMMU: simplify unmap-on-error in iommu_map() > 03: IOMMU: add order parameter to ->{,un}map_page() hooks > 04: IOMMU: have iommu_{,un}map() split requests into largest possible chunks
These first 4 patches are in principle ready to go in. If only there wasn't (sadly once again) the unclear state with comments on the first 2 that you had given on Apr 27. I did reply verbally, and hence I'm intending to commit these 4 by the end of the week - on the assumption that no response to my replies means I've sufficiently addressed the concerns - unless I hear back otherwise. Thanks for you understanding, Jan
