From 5e8d4e0c47c44cdfde985b665790655554340fde Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Wed, 26 Feb 2025 14:22:57 +0100 Subject: [PATCH] mm/mmu_notifier: use MMU_NOTIFY_CLEAR in remove_device_exclusive_entry() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Let's limit the use of MMU_NOTIFY_EXCLUSIVE to the case where we convert a present PTE to device-exclusive. For the other case, we can simply use MMU_NOTIFY_CLEAR, because it really is clearing the device-exclusive entry first, to then install the present entry. Update the documentation of MMU_NOTIFY_EXCLUSIVE, to document the single use case more thoroughly. If ever required, we could add a separate MMU_NOTIFY_CLEAR_EXCLUSIVE; for now using MMU_NOTIFY_CLEAR seems to be sufficient. Link: https://lkml.kernel.org/r/20250226132257.2826043-6-david@redhat.com Signed-off-by: David Hildenbrand Cc: Alistair Popple Cc: Jason Gunthorpe Cc: Jérôme Glisse Signed-off-by: Andrew Morton --- include/linux/mmu_notifier.h | 8 ++++---- mm/memory.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index d4e714661826..bc2402a45741 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -43,10 +43,10 @@ struct mmu_interval_notifier; * a device driver to possibly ignore the invalidation if the * owner field matches the driver's device private pgmap owner. * - * @MMU_NOTIFY_EXCLUSIVE: to signal a device driver that the device will no - * longer have exclusive access to the page. When sent during creation of an - * exclusive range the owner will be initialised to the value provided by the - * caller of make_device_exclusive(), otherwise the owner will be NULL. + * @MMU_NOTIFY_EXCLUSIVE: conversion of a page table entry to device-exclusive. + * The owner is initialized to the value provided by the caller of + * make_device_exclusive(), such that this caller can filter out these + * events. */ enum mmu_notifier_event { MMU_NOTIFY_UNMAP = 0, diff --git a/mm/memory.c b/mm/memory.c index cb9549477556..1efc393e32b6 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4048,7 +4048,7 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf) folio_put(folio); return ret; } - mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, + mmu_notifier_range_init_owner(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, vmf->address & PAGE_MASK, (vmf->address & PAGE_MASK) + PAGE_SIZE, NULL); mmu_notifier_invalidate_range_start(&range); -- 2.49.0