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authorPaolo Bonzini <pbonzini@redhat.com>2019-04-17 15:28:44 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2019-04-30 21:22:15 +0200
commit76d58e0f07ec203bbdfcaabd9a9fc10a5a3ed5ea (patch)
tree8cf55a1022132806b63cceb24b286514c2210e34 /Documentation/virtual/kvm
parent0699c64a4be6e4a6137240379a1f82c752e663d8 (diff)
KVM: fix KVM_CLEAR_DIRTY_LOG for memory slots of unaligned size
If a memory slot's size is not a multiple of 64 pages (256K), then the KVM_CLEAR_DIRTY_LOG API is unusable: clearing the final 64 pages either requires the requested page range to go beyond memslot->npages, or requires log->num_pages to be unaligned, and kvm_clear_dirty_log_protect requires log->num_pages to be both in range and aligned. To allow this case, allow log->num_pages not to be a multiple of 64 if it ends exactly on the last page of the slot. Reported-by: Peter Xu <peterx@redhat.com> Fixes: 98938aa8edd6 ("KVM: validate userspace input in kvm_clear_dirty_log_protect()", 2019-01-02) Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virtual/kvm')
-rw-r--r--Documentation/virtual/kvm/api.txt5
1 files changed, 3 insertions, 2 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 7f3ebc9e7cee..64b38dfcc243 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3830,8 +3830,9 @@ The ioctl clears the dirty status of pages in a memory slot, according to
the bitmap that is passed in struct kvm_clear_dirty_log's dirty_bitmap
field. Bit 0 of the bitmap corresponds to page "first_page" in the
memory slot, and num_pages is the size in bits of the input bitmap.
-Both first_page and num_pages must be a multiple of 64. For each bit
-that is set in the input bitmap, the corresponding page is marked "clean"
+first_page must be a multiple of 64; num_pages must also be a multiple of
+64 unless first_page + num_pages is the size of the memory slot. For each
+bit that is set in the input bitmap, the corresponding page is marked "clean"
in KVM's dirty bitmap, and dirty tracking is re-enabled for that page
(for example via write-protection, or by clearing the dirty bit in
a page table entry).