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KVM: guest_memfd: Return early if range already has requested attributes

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Provide a function to check that a range has given attributes.

Optimize setting memory attributes by returning early if all pages in the
requested range already have the requested attributes.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
Link: https://patch.msgid.link/20260910-gmem-inplace-conversion-v13-17-dd6fbf94f4e1@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Ackerley Tng 2026-09-10 16:55:43 -07:00 committed by Sean Christopherson
parent 6fa1dab756
commit 856852ef21
1 changed files with 22 additions and 1 deletions
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23
virt/kvm/guest_memfd.c
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@ -99,6 +99,24 @@ static bool kvm_gmem_is_shared_mem(struct inode *inode, pgoff_t index)
return !kvm_gmem_is_private_mem(inode, index);
}
static bool kvm_gmem_range_has_attributes(struct inode *inode,
pgoff_t index, size_t nr_pages,
u64 attributes)
{
struct maple_tree *mt = &GMEM_I(inode)->attributes;
pgoff_t end = index + nr_pages - 1;
void *entry;
lockdep_assert(mt_lock_is_held(mt));
mt_for_each(mt, entry, index, end) {
if (kvm_gmem_get_attributes(inode, entry) != attributes)
return false;
}
return true;
}
/*
* Returns a locked folio on success. The caller is responsible for
* setting the up-to-date flag before the memory is mapped into the guest.
@ -675,12 +693,15 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
pgoff_t end = start + nr_pages;
struct maple_tree *mt;
struct ma_state mas;
int r;
int r = 0;
mt = &gi->attributes;
filemap_invalidate_lock(mapping);
if (kvm_gmem_range_has_attributes(inode, start, nr_pages, attrs))
goto out;
mas_init(&mas, mt, start);
r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages);
if (r) {