From: David Hildenbrand <da...@redhat.com>
When unregistering uffd-wp, older kernels before commit f369b07c86143
("mm/uffd:reset write protection when unregister with wp-mode") won't
clear the uffd-wp PTE bit. When re-registering uffd-wp, the previous
uffd-wp PTE bits would trigger again. With above commit, the kernel will
clear the uffd-wp PTE bits when unregistering itself.
Consequently, we'll clear the uffd-wp PTE bits now twice -- whereby we
don't care about clearing them at all: a new background snapshot will
re-register uffd-wp and re-protect all memory either way.
So let's skip the manual clearing of uffd-wp. If ever relevant, we
could clear conditionally in uffd_unregister_memory() -- we just need a
way to figure out more recent kernels.
Reviewed-by: Peter Xu <pet...@redhat.com>
Reviewed-by: Juan Quintela <quint...@redhat.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
Signed-off-by: Juan Quintela <quint...@redhat.com>
---
migration/ram.c | 9 ---------
1 file changed, 9 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 73e5ca93e5..efaae07dd8 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1918,12 +1918,6 @@ fail:
if ((block->flags & RAM_UF_WRITEPROTECT) == 0) {
continue;
}
- /*
- * In case some memory block failed to be write-protected
- * remove protection and unregister all succeeded RAM blocks
- */
- uffd_change_protection(rs->uffdio_fd, block->host, block->max_length,
- false, false);
uffd_unregister_memory(rs->uffdio_fd, block->host, block->max_length);
/* Cleanup flags and remove reference */
block->flags &= ~RAM_UF_WRITEPROTECT;
@@ -1949,9 +1943,6 @@ void ram_write_tracking_stop(void)
if ((block->flags & RAM_UF_WRITEPROTECT) == 0) {
continue;
}
- /* Remove protection and unregister all affected RAM blocks */
- uffd_change_protection(rs->uffdio_fd, block->host, block->max_length,
- false, false);
uffd_unregister_memory(rs->uffdio_fd, block->host, block->max_length);
trace_ram_write_tracking_ramblock_stop(block->idstr, block->page_size,
--
2.39.1
