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[PATCH v1 3/5] migration/ram: Don't explicitly unprotect when unregister
From: |
David Hildenbrand |
Subject: |
[PATCH v1 3/5] migration/ram: Don't explicitly unprotect when unregistering uffd-wp |
Date: |
Thu, 5 Jan 2023 13:45:26 +0100 |
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.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
migration/ram.c | 9 ---------
1 file changed, 9 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 6e4e41952a..6a3dbee2c3 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,
--
2.39.0
- [PATCH v1 0/5] migration/ram: background snapshot fixes and optimiations, David Hildenbrand, 2023/01/05
- [PATCH v1 1/5] migration/ram: Fix populate_read_range(), David Hildenbrand, 2023/01/05
- [PATCH v1 4/5] migration/ram: Rely on used_length for uffd_change_protection(), David Hildenbrand, 2023/01/05
- [PATCH v1 2/5] migration/ram: Fix error handling in ram_write_tracking_start(), David Hildenbrand, 2023/01/05
- [PATCH v1 3/5] migration/ram: Don't explicitly unprotect when unregistering uffd-wp,
David Hildenbrand <=
- [PATCH v1 5/5] migration/ram: Optimize ram_write_tracking_start() for RamDiscardManager, David Hildenbrand, 2023/01/05
- Re: [PATCH v1 0/5] migration/ram: background snapshot fixes and optimiations, Peter Xu, 2023/01/05
- Re: [PATCH v1 0/5] migration/ram: background snapshot fixes and optimiations, David Hildenbrand, 2023/01/23