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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: David 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: Andrew Morton <akpm@linux-foundation.org>
pull/1193/head
David Hildenbrand 2025-02-26 14:22:57 +01:00 committed by Andrew Morton
parent 2f95381f8a
commit 720ba85040
2 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/mmu_notifier.h
View File

@ -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,

2
mm/memory.c
View File

@ -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);