kernel/linux.git/drivers/xen/gntdev.c, branch v6.19.11

Merge tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-10-03T01:18:33+00:00

Pull MM updates from Andrew Morton: - "mm, swap: improve cluster scan strategy" from Kairui Song improves performance and reduces the failure rate of swap cluster allocation - "support large align and nid in Rust allocators" from Vitaly Wool permits Rust allocators to set NUMA node and large alignment when perforning slub and vmalloc reallocs - "mm/damon/vaddr: support stat-purpose DAMOS" from Yueyang Pan extend DAMOS_STAT's handling of the DAMON operations sets for virtual address spaces for ops-level DAMOS filters - "execute PROCMAP_QUERY ioctl under per-vma lock" from Suren Baghdasaryan reduces mmap_lock contention during reads of /proc/pid/maps - "mm/mincore: minor clean up for swap cache checking" from Kairui Song performs some cleanup in the swap code - "mm: vm_normal_page*() improvements" from David Hildenbrand provides code cleanup in the pagemap code - "add persistent huge zero folio support" from Pankaj Raghav provides a block layer speedup by optionalls making the huge_zero_pagepersistent, instead of releasing it when its refcount falls to zero - "kho: fixes and cleanups" from Mike Rapoport adds a few touchups to the recently added Kexec Handover feature - "mm: make mm->flags a bitmap and 64-bit on all arches" from Lorenzo Stoakes turns mm_struct.flags into a bitmap. To end the constant struggle with space shortage on 32-bit conflicting with 64-bit's needs - "mm/swapfile.c and swap.h cleanup" from Chris Li cleans up some swap code - "selftests/mm: Fix false positives and skip unsupported tests" from Donet Tom fixes a few things in our selftests code - "prctl: extend PR_SET_THP_DISABLE to only provide THPs when advised" from David Hildenbrand "allows individual processes to opt-out of THP=always into THP=madvise, without affecting other workloads on the system". It's a long story - the [1/N] changelog spells out the considerations - "Add and use memdesc_flags_t" from Matthew Wilcox gets us started on the memdesc project. Please see https://kernelnewbies.org/MatthewWilcox/Memdescs and https://blogs.oracle.com/linux/post/introducing-memdesc - "Tiny optimization for large read operations" from Chi Zhiling improves the efficiency of the pagecache read path - "Better split_huge_page_test result check" from Zi Yan improves our folio splitting selftest code - "test that rmap behaves as expected" from Wei Yang adds some rmap selftests - "remove write_cache_pages()" from Christoph Hellwig removes that function and converts its two remaining callers - "selftests/mm: uffd-stress fixes" from Dev Jain fixes some UFFD selftests issues - "introduce kernel file mapped folios" from Boris Burkov introduces the concept of "kernel file pages". Using these permits btrfs to account its metadata pages to the root cgroup, rather than to the cgroups of random inappropriate tasks - "mm/pageblock: improve readability of some pageblock handling" from Wei Yang provides some readability improvements to the page allocator code - "mm/damon: support ARM32 with LPAE" from SeongJae Park teaches DAMON to understand arm32 highmem - "tools: testing: Use existing atomic.h for vma/maple tests" from Brendan Jackman performs some code cleanups and deduplication under tools/testing/ - "maple_tree: Fix testing for 32bit compiles" from Liam Howlett fixes a couple of 32-bit issues in tools/testing/radix-tree.c - "kasan: unify kasan_enabled() and remove arch-specific implementations" from Sabyrzhan Tasbolatov moves KASAN arch-specific initialization code into a common arch-neutral implementation - "mm: remove zpool" from Johannes Weiner removes zspool - an indirection layer which now only redirects to a single thing (zsmalloc) - "mm: task_stack: Stack handling cleanups" from Pasha Tatashin makes a couple of cleanups in the fork code - "mm: remove nth_page()" from David Hildenbrand makes rather a lot of adjustments at various nth_page() callsites, eventually permitting the removal of that undesirable helper function - "introduce kasan.write_only option in hw-tags" from Yeoreum Yun creates a KASAN read-only mode for ARM, using that architecture's memory tagging feature. It is felt that a read-only mode KASAN is suitable for use in production systems rather than debug-only - "mm: hugetlb: cleanup hugetlb folio allocation" from Kefeng Wang does some tidying in the hugetlb folio allocation code - "mm: establish const-correctness for pointer parameters" from Max Kellermann makes quite a number of the MM API functions more accurate about the constness of their arguments. This was getting in the way of subsystems (in this case CEPH) when they attempt to improving their own const/non-const accuracy - "Cleanup free_pages() misuse" from Vishal Moola fixes a number of code sites which were confused over when to use free_pages() vs __free_pages() - "Add Rust abstraction for Maple Trees" from Alice Ryhl makes the mapletree code accessible to Rust. Required by nouveau and by its forthcoming successor: the new Rust Nova driver - "selftests/mm: split_huge_page_test: split_pte_mapped_thp improvements" from David Hildenbrand adds a fix and some cleanups to the thp selftesting code - "mm, swap: introduce swap table as swap cache (phase I)" from Chris Li and Kairui Song is the first step along the path to implementing "swap tables" - a new approach to swap allocation and state tracking which is expected to yield speed and space improvements. This patchset itself yields a 5-20% performance benefit in some situations - "Some ptdesc cleanups" from Matthew Wilcox utilizes the new memdesc layer to clean up the ptdesc code a little - "Fix va_high_addr_switch.sh test failure" from Chunyu Hu fixes some issues in our 5-level pagetable selftesting code - "Minor fixes for memory allocation profiling" from Suren Baghdasaryan addresses a couple of minor issues in relatively new memory allocation profiling feature - "Small cleanups" from Matthew Wilcox has a few cleanups in preparation for more memdesc work - "mm/damon: add addr_unit for DAMON_LRU_SORT and DAMON_RECLAIM" from Quanmin Yan makes some changes to DAMON in furtherance of supporting arm highmem - "selftests/mm: Add -Wunreachable-code and fix warnings" from Muhammad Anjum adds that compiler check to selftests code and fixes the fallout, by removing dead code - "Improvements to Victim Process Thawing and OOM Reaper Traversal Order" from zhongjinji makes a number of improvements in the OOM killer: mainly thawing a more appropriate group of victim threads so they can release resources - "mm/damon: misc fixups and improvements for 6.18" from SeongJae Park is a bunch of small and unrelated fixups for DAMON - "mm/damon: define and use DAMON initialization check function" from SeongJae Park implement reliability and maintainability improvements to a recently-added bug fix - "mm/damon/stat: expose auto-tuned intervals and non-idle ages" from SeongJae Park provides additional transparency to userspace clients of the DAMON_STAT information - "Expand scope of khugepaged anonymous collapse" from Dev Jain removes some constraints on khubepaged's collapsing of anon VMAs. It also increases the success rate of MADV_COLLAPSE against an anon vma - "mm: do not assume file == vma->vm_file in compat_vma_mmap_prepare()" from Lorenzo Stoakes moves us further towards removal of file_operations.mmap(). This patchset concentrates upon clearing up the treatment of stacked filesystems - "mm: Improve mlock tracking for large folios" from Kiryl Shutsemau provides some fixes and improvements to mlock's tracking of large folios. /proc/meminfo's "Mlocked" field became more accurate - "mm/ksm: Fix incorrect accounting of KSM counters during fork" from Donet Tom fixes several user-visible KSM stats inaccuracies across forks and adds selftest code to verify these counters - "mm_slot: fix the usage of mm_slot_entry" from Wei Yang addresses some potential but presently benign issues in KSM's mm_slot handling * tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (372 commits) mm: swap: check for stable address space before operating on the VMA mm: convert folio_page() back to a macro mm/khugepaged: use start_addr/addr for improved readability hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list alloc_tag: fix boot failure due to NULL pointer dereference mm: silence data-race in update_hiwater_rss mm/memory-failure: don't select MEMORY_ISOLATION mm/khugepaged: remove definition of struct khugepaged_mm_slot mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL hugetlb: increase number of reserving hugepages via cmdline selftests/mm: add fork inheritance test for ksm_merging_pages counter mm/ksm: fix incorrect KSM counter handling in mm_struct during fork drivers/base/node: fix double free in register_one_node() mm: remove PMD alignment constraint in execmem_vmalloc() mm/memory_hotplug: fix typo 'esecially' -> 'especially' mm/rmap: improve mlock tracking for large folios mm/filemap: map entire large folio faultaround mm/fault: try to map the entire file folio in finish_fault() mm/rmap: mlock large folios in try_to_unmap_one() mm/rmap: fix a mlock race condition in folio_referenced_one() ...

mm: rename vm_ops->find_special_page() to vm_ops->find_normal_page()

2025-09-13T23:54:53+00:00

... and hide it behind a kconfig option. There is really no need for any !xen code to perform this check. The naming is a bit off: we want to find the "normal" page when a PTE was marked "special". So it's really not "finding a special" page. Improve the documentation, and add a comment in the code where XEN ends up performing the pte_mkspecial() through a hypercall. More details can be found in commit 923b2919e2c3 ("xen/gntdev: mark userspace PTEs as special on x86 PV guests"). Link: https://lkml.kernel.org/r/20250811112631.759341-12-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Oscar Salvador Reviewed-by: Lorenzo Stoakes Reviewed-by: Wei Yang Cc: David Vrabel Cc: Alistair Popple Cc: Al Viro Cc: Baolin Wang Cc: Barry Song Cc: Christian Brauner Cc: Christophe Leroy Cc: Dan Williams Cc: Dev Jain Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Juegren Gross Cc: Lance Yang Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Mariano Pache Cc: Matthew Wilcox (Oracle) Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Oleksandr Tyshchenko Cc: Ryan Roberts Cc: Stefano Stabellini Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton

drivers/xen/gntdev: use xen_pv_domain() instead of cached value

2025-09-08T15:01:36+00:00

Eliminate the use_ptemod variable by replacing its use cases with xen_pv_domain(). Instead of passing the xen_pv_domain() return value to gntdev_ioctl_dmabuf_exp_from_refs(), use xen_pv_domain() in that function. Reviewed-by: Jason Andryuk Signed-off-by: Juergen Gross Message-ID: <20250826145608.10352-4-jgross@suse.com>

xen: replace XENFEAT_auto_translated_physmap with xen_pv_domain()

2025-09-08T15:01:36+00:00

Instead of testing the XENFEAT_auto_translated_physmap feature, just use !xen_pv_domain() which is equivalent. This has the advantage that a kernel not built with CONFIG_XEN_PV will be smaller due to dead code elimination. Reviewed-by: Jason Andryuk Signed-off-by: Juergen Gross Message-ID: <20250826145608.10352-3-jgross@suse.com>

xen/gntdev: remove struct gntdev_copy_batch from stack

2025-07-14T15:10:09+00:00

When compiling the kernel with LLVM, the following warning was issued: drivers/xen/gntdev.c:991: warning: stack frame size (1160) exceeds limit (1024) in function 'gntdev_ioctl' The main reason is struct gntdev_copy_batch which is located on the stack and has a size of nearly 1kb. For performance reasons it shouldn't by just dynamically allocated instead, so allocate a new instance when needed and instead of freeing it put it into a list of free structs anchored in struct gntdev_priv. Fixes: a4cdb556cae0 ("xen/gntdev: add ioctl for grant copy") Reported-by: Abinash Singh Reviewed-by: Stefano Stabellini Signed-off-by: Juergen Gross Message-ID: <20250703073259.17356-1-jgross@suse.com>

mm: replace vma->vm_flags direct modifications with modifier calls

2023-02-10T00:51:39+00:00

Replace direct modifications to vma->vm_flags with calls to modifier functions to be able to track flag changes and to keep vma locking correctness. [akpm@linux-foundation.org: fix drivers/misc/open-dice.c, per Hyeonggon Yoo] Link: https://lkml.kernel.org/r/20230126193752.297968-5-surenb@google.com Signed-off-by: Suren Baghdasaryan Acked-by: Michal Hocko Acked-by: Mel Gorman Acked-by: Mike Rapoport (IBM) Acked-by: Sebastian Reichel Reviewed-by: Liam R. Howlett Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Andy Lutomirski Cc: Arjun Roy Cc: Axel Rasmussen Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: David Rientjes Cc: Eric Dumazet Cc: Greg Thelen Cc: Hugh Dickins Cc: Ingo Molnar Cc: Jann Horn Cc: Joel Fernandes Cc: Johannes Weiner Cc: Kent Overstreet Cc: Laurent Dufour Cc: Lorenzo Stoakes Cc: Matthew Wilcox Cc: Minchan Kim Cc: Paul E. McKenney Cc: Peter Oskolkov Cc: Peter Xu Cc: Peter Zijlstra Cc: Punit Agrawal Cc: Sebastian Andrzej Siewior Cc: Shakeel Butt Cc: Soheil Hassas Yeganeh Cc: Song Liu Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton

xen/gntdev: Accommodate VMA splitting

2022-10-06T08:40:21+00:00

Prior to this commit, the gntdev driver code did not handle the following scenario correctly with paravirtualized (PV) Xen domains: * User process sets up a gntdev mapping composed of two grant mappings (i.e., two pages shared by another Xen domain). * User process munmap()s one of the pages. * User process munmap()s the remaining page. * User process exits. In the scenario above, the user process would cause the kernel to log the following messages in dmesg for the first munmap(), and the second munmap() call would result in similar log messages: BUG: Bad page map in process doublemap.test pte:... pmd:... page:0000000057c97bff refcount:1 mapcount:-1 \ mapping:0000000000000000 index:0x0 pfn:... ... page dumped because: bad pte ... file:gntdev fault:0x0 mmap:gntdev_mmap [xen_gntdev] readpage:0x0 ... Call Trace: dump_stack_lvl+0x46/0x5e print_bad_pte.cold+0x66/0xb6 unmap_page_range+0x7e5/0xdc0 unmap_vmas+0x78/0xf0 unmap_region+0xa8/0x110 __do_munmap+0x1ea/0x4e0 __vm_munmap+0x75/0x120 __x64_sys_munmap+0x28/0x40 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x61/0xcb ... For each munmap() call, the Xen hypervisor (if built with CONFIG_DEBUG) would print out the following and trigger a general protection fault in the affected Xen PV domain: (XEN) d0v... Attempt to implicitly unmap d0's grant PTE ... (XEN) d0v... Attempt to implicitly unmap d0's grant PTE ... As of this writing, gntdev_grant_map structure's vma field (referred to as map->vma below) is mainly used for checking the start and end addresses of mappings. However, with split VMAs, these may change, and there could be more than one VMA associated with a gntdev mapping. Hence, remove the use of map->vma and rely on map->pages_vm_start for the original start address and on (map->count << PAGE_SHIFT) for the original mapping size. Let the invalidate() and find_special_page() hooks use these. Also, given that there can be multiple VMAs associated with a gntdev mapping, move the "mmu_interval_notifier_remove(&map->notifier)" call to the end of gntdev_put_map, so that the MMU notifier is only removed after the closing of the last remaining VMA. Finally, use an atomic to prevent inadvertent gntdev mapping re-use, instead of using the map->live_grants atomic counter and/or the map->vma pointer (the latter of which is now removed). This prevents the userspace from mmap()'ing (with MAP_FIXED) a gntdev mapping over the same address range as a previously set up gntdev mapping. This scenario can be summarized with the following call-trace, which was valid prior to this commit: mmap gntdev_mmap mmap (repeat mmap with MAP_FIXED over the same address range) gntdev_invalidate unmap_grant_pages (sets 'being_removed' entries to true) gnttab_unmap_refs_async unmap_single_vma gntdev_mmap (maps the shared pages again) munmap gntdev_invalidate unmap_grant_pages (no-op because 'being_removed' entries are true) unmap_single_vma (For PV domains, Xen reports that a granted page is being unmapped and triggers a general protection fault in the affected domain, if Xen was built with CONFIG_DEBUG) The fix for this last scenario could be worth its own commit, but we opted for a single commit, because removing the gntdev_grant_map structure's vma field requires guarding the entry to gntdev_mmap(), and the live_grants atomic counter is not sufficient on its own to prevent the mmap() over a pre-existing mapping. Link: https://github.com/QubesOS/qubes-issues/issues/7631 Fixes: ab31523c2fca ("xen/gntdev: allow usermode to map granted pages") Cc: stable@vger.kernel.org Signed-off-by: M. Vefa Bicakci Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20221002222006.2077-3-m.v.b@runbox.com Signed-off-by: Juergen Gross

xen/gntdev: Prevent leaking grants

2022-10-06T08:40:16+00:00

Prior to this commit, if a grant mapping operation failed partially, some of the entries in the map_ops array would be invalid, whereas all of the entries in the kmap_ops array would be valid. This in turn would cause the following logic in gntdev_map_grant_pages to become invalid: for (i = 0; i < map->count; i++) { if (map->map_ops[i].status == GNTST_okay) { map->unmap_ops[i].handle = map->map_ops[i].handle; if (!use_ptemod) alloced++; } if (use_ptemod) { if (map->kmap_ops[i].status == GNTST_okay) { if (map->map_ops[i].status == GNTST_okay) alloced++; map->kunmap_ops[i].handle = map->kmap_ops[i].handle; } } } ... atomic_add(alloced, &map->live_grants); Assume that use_ptemod is true (i.e., the domain mapping the granted pages is a paravirtualized domain). In the code excerpt above, note that the "alloced" variable is only incremented when both kmap_ops[i].status and map_ops[i].status are set to GNTST_okay (i.e., both mapping operations are successful). However, as also noted above, there are cases where a grant mapping operation fails partially, breaking the assumption of the code excerpt above. The aforementioned causes map->live_grants to be incorrectly set. In some cases, all of the map_ops mappings fail, but all of the kmap_ops mappings succeed, meaning that live_grants may remain zero. This in turn makes it impossible to unmap the successfully grant-mapped pages pointed to by kmap_ops, because unmap_grant_pages has the following snippet of code at its beginning: if (atomic_read(&map->live_grants) == 0) return; /* Nothing to do */ In other cases where only some of the map_ops mappings fail but all kmap_ops mappings succeed, live_grants is made positive, but when the user requests unmapping the grant-mapped pages, __unmap_grant_pages_done will then make map->live_grants negative, because the latter function does not check if all of the pages that were requested to be unmapped were actually unmapped, and the same function unconditionally subtracts "data->count" (i.e., a value that can be greater than map->live_grants) from map->live_grants. The side effects of a negative live_grants value have not been studied. The net effect of all of this is that grant references are leaked in one of the above conditions. In Qubes OS v4.1 (which uses Xen's grant mechanism extensively for X11 GUI isolation), this issue manifests itself with warning messages like the following to be printed out by the Linux kernel in the VM that had granted pages (that contain X11 GUI window data) to dom0: "g.e. 0x1234 still pending", especially after the user rapidly resizes GUI VM windows (causing some grant-mapping operations to partially or completely fail, due to the fact that the VM unshares some of the pages as part of the window resizing, making the pages impossible to grant-map from dom0). The fix for this issue involves counting all successful map_ops and kmap_ops mappings separately, and then adding the sum to live_grants. During unmapping, only the number of successfully unmapped grants is subtracted from live_grants. The code is also modified to check for negative live_grants values after the subtraction and warn the user. Link: https://github.com/QubesOS/qubes-issues/issues/7631 Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()") Cc: stable@vger.kernel.org Signed-off-by: M. Vefa Bicakci Acked-by: Demi Marie Obenour Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20221002222006.2077-2-m.v.b@runbox.com Signed-off-by: Juergen Gross

xen/gntdev: Ignore failure to unmap INVALID_GRANT_HANDLE

2022-07-11T09:39:45+00:00

The error paths of gntdev_mmap() can call unmap_grant_pages() even though not all of the pages have been successfully mapped. This will trigger the WARN_ON()s in __unmap_grant_pages_done(). The number of warnings can be very large; I have observed thousands of lines of warnings in the systemd journal. Avoid this problem by only warning on unmapping failure if the handle being unmapped is not INVALID_GRANT_HANDLE. The handle field of any page that was not successfully mapped will be INVALID_GRANT_HANDLE, so this catches all cases where unmapping can legitimately fail. Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()") Cc: stable@vger.kernel.org Suggested-by: Juergen Gross Signed-off-by: Demi Marie Obenour Reviewed-by: Oleksandr Tyshchenko Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20220710230522.1563-1-demi@invisiblethingslab.com Signed-off-by: Juergen Gross

xen/gntdev: Avoid blocking in unmap_grant_pages()

2022-06-23T13:29:18+00:00

unmap_grant_pages() currently waits for the pages to no longer be used. In https://github.com/QubesOS/qubes-issues/issues/7481, this lead to a deadlock against i915: i915 was waiting for gntdev's MMU notifier to finish, while gntdev was waiting for i915 to free its pages. I also believe this is responsible for various deadlocks I have experienced in the past. Avoid these problems by making unmap_grant_pages async. This requires making it return void, as any errors will not be available when the function returns. Fortunately, the only use of the return value is a WARN_ON(), which can be replaced by a WARN_ON when the error is detected. Additionally, a failed call will not prevent further calls from being made, but this is harmless. Because unmap_grant_pages is now async, the grant handle will be sent to INVALID_GRANT_HANDLE too late to prevent multiple unmaps of the same handle. Instead, a separate bool array is allocated for this purpose. This wastes memory, but stuffing this information in padding bytes is too fragile. Furthermore, it is necessary to grab a reference to the map before making the asynchronous call, and release the reference when the call returns. It is also necessary to guard against reentrancy in gntdev_map_put(), and to handle the case where userspace tries to map a mapping whose contents have not all been freed yet. Fixes: 745282256c75 ("xen/gntdev: safely unmap grants in case they are still in use") Cc: stable@vger.kernel.org Signed-off-by: Demi Marie Obenour Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20220622022726.2538-1-demi@invisiblethingslab.com Signed-off-by: Juergen Gross