Commit 720ba850 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/mmu_notifier: use MMU_NOTIFY_CLEAR in remove_device_exclusive_entry() 

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: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 2f95381f

include/linux/mmu_notifier.h

+4 −4
Original line number Diff line number Diff line
@@ -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,

mm/memory.c

+1 −1
Original line number Diff line number Diff line
@@ -4003,7 +4003,7 @@ 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);