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mm, virt: merge AS_UNMOVABLE and AS_INACCESSIBLE

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The flags AS_UNMOVABLE and AS_INACCESSIBLE were both added just for guest_memfd;
AS_UNMOVABLE is already in existing versions of Linux, while AS_INACCESSIBLE was
acked for inclusion in 6.11.

But really, they are the same thing: only guest_memfd uses them, at least for
now, and guest_memfd pages are unmovable because they should not be
accessed by the CPU.

So merge them into one; use the AS_INACCESSIBLE name which is more comprehensive.
At the same time, this fixes an embarrassing bug where AS_INACCESSIBLE was used
as a bit mask, despite it being just a bit index.

The bug was mostly benign, because AS_INACCESSIBLE's bit representation (1010)
corresponded to setting AS_UNEVICTABLE (which is already set) and AS_ENOSPC
(except no async writes can happen on the guest_memfd).  So the AS_INACCESSIBLE
flag simply had no effect.

Fixes: 1d23040caa ("KVM: guest_memfd: Use AS_INACCESSIBLE when creating guest_memfd inode")
Fixes: c72ceafbd1 ("mm: Introduce AS_INACCESSIBLE for encrypted/confidential memory")
Cc: linux-mm@kvack.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Michael Roth <michael.roth@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini
2024-07-11 13:56:54 -04:00
parent 02b0d3b9d4
commit 27e6a24a4c
5 changed files with 16 additions and 17 deletions
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3
virt/kvm/guest_memfd.c
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@@ -416,11 +416,10 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
inode->i_private = (void *)(unsigned long)flags;
inode->i_op = &kvm_gmem_iops;
inode->i_mapping->a_ops = &kvm_gmem_aops;
inode->i_mapping->flags |= AS_INACCESSIBLE;
inode->i_mode |= S_IFREG;
inode->i_size = size;
mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
mapping_set_unmovable(inode->i_mapping);
mapping_set_inaccessible(inode->i_mapping);
/* Unmovable mappings are supposed to be marked unevictable as well. */
WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));