RFC s390: fixes, cleanups and optimizations for page table walkers
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- v1 RFC Latest9 patches 18 repliesIn review
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/9 | s390/gmap: validate VMA in __gmap_zap()arch/ | +6 | 1 reply | |
| 2/9 | s390/gmap: don't unconditionally call pte_unmap_unlock() in __gmap_zap()arch/ | +3 | 1 reply | |
| 3/9 | s390/mm: validate VMA in PGSTE manipulation functionsarch/ | +13 | 1 reply | |
| 4/9 | s390/mm: fix VMA and page table handling code in storage key handling functionsarch/ | +39 | 1 reply | |
| 5/9 | s390/uv: fully validate the VMA before calling follow_page()arch/ | +1 | 2 replies | |
| 6/9 | s390/pci_mmio: fully validate the VMA before calling follow_pte()arch/ | +2 | 2 replies | |
| 7/9 | s390/mm: no need for pte_alloc_map_lock() if we know the pmd is presentarch/ | +3 | 2 replies | |
| 8/9 | s390/mm: optimize set_guest_storage_key()arch/ | +12 | 1 reply | |
| 9/9 | s390/mm: optimize reset_guest_reference_bit()arch/ | +12 | 1 reply |
Reviews trailers per patch
8 of 9 patches have a Reviewed-by or Acked-by of their own; the series has one for all of them.
| Patch | Claudio Imbrenda | Liam R. Howlett | Heiko Carstens |
|---|---|---|---|
| Series | A-b | ||
| 1/9 | R-b | ||
| 2/9 | R-b | ||
| 3/9 | R-b | ||
| 4/9 | R-b | ||
| 5/9 | R-b | Reviwed-by | |
| 6/9 | R-b | R-b | |
| 7/9 | |||
| 8/9 | R-b | ||
| 9/9 | R-b |
Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes. Scroll the table sideways for all 3 reviewers.
Cover letter [PATCH resend RFC 0/9] s390: fixes, cleanups and optimizations for page table walkers
Resend because I missed ccing people on the actual patches ...
RFC because the patches are essentially untested and I did not actually try to trigger any of the things these patches are supposed to fix. It merely matches my current understanding (and what other code does :) ). I did compile-test as far as possible.
After learning more about the wonderful world of page tables and their interaction with the mmap_sem and VMAs, I spotted some issues in our page table walkers that allow user space to trigger nasty behavior when playing dirty tricks with munmap() or mmap() of hugetlb. While some issues should be hard to trigger, others are fairly easy because we provide conventient interfaces (e.g., KVM_S390_GET_SKEYS and KVM_S390_SET_SKEYS).
Future work:
- Don't use get_locked_pte() when it's not required to actually allocate page tables -- similar to how storage keys are now handled. Examples are get_pgste() and __gmap_zap.
- Don't use get_locked_pte() and instead let page fault logic allocate page tables when we actually do need page tables -- also, similar to how storage keys are now handled. Examples are set_pgste_bits() and pgste_perform_essa().
- Maybe switch to mm/pagewalk.c to avoid custom page table walkers. For __gmap_zap() that's very easy.
David Hildenbrand (9):
s390/gmap: validate VMA in __gmap_zap() s390/gmap: don't unconditionally call pte_unmap_unlock() in
__gmap_zap()
s390/mm: validate VMA in PGSTE manipulation functions s390/mm: fix VMA and page table handling code in storage key handling
functions
s390/uv: fully validate the VMA before calling follow_page() s390/pci_mmio: fully validate the VMA before calling follow_pte() s390/mm: no need for pte_alloc_map_lock() if we know the pmd is
present
s390/mm: optimize set_guest_storage_key()
s390/mm: optimize reset_guest_reference_bit()
arch/s390/kernel/uv.c | 2 +- arch/s390/mm/gmap.c | 11 +++- arch/s390/mm/pgtable.c | 109 +++++++++++++++++++++++++++------------ arch/s390/pci/pci_mmio.c | 4 +- 4 files changed, 89 insertions(+), 37 deletions(-)
base-commit: 7d2a07b769330c34b4deabeed939325c77a7ec2f
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2.31.1