On 03/15/2018 02:11 AM, Dr. David Alan Gilbert wrote:
* Wei Wang (wei.w.w...@intel.com) wrote:
This patch adds an API to clear bits corresponding to guest free pages
from the dirty bitmap. Spilt the free page block if it crosses the QEMU
RAMBlock boundary.
Signed-off-by: Wei Wang <wei.w.w...@intel.com>
CC: Dr. David Alan Gilbert <dgilb...@redhat.com>
CC: Juan Quintela <quint...@redhat.com>
CC: Michael S. Tsirkin <m...@redhat.com>
---
include/migration/misc.h | 2 ++
migration/ram.c | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+)
diff --git a/include/migration/misc.h b/include/migration/misc.h
index 77fd4f5..fae1acf 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -14,11 +14,13 @@
#ifndef MIGRATION_MISC_H
#define MIGRATION_MISC_H
+#include "exec/cpu-common.h"
#include "qemu/notify.h"
/* migration/ram.c */
void ram_mig_init(void);
+void qemu_guest_free_page_hint(void *addr, size_t len);
/* migration/block.c */
diff --git a/migration/ram.c b/migration/ram.c
index 5e33e5c..e172798 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2189,6 +2189,27 @@ static int ram_init_all(RAMState **rsp)
return 0;
}
This could do with some comments
OK, I'll add some.
+void qemu_guest_free_page_hint(void *addr, size_t len)
+{
+ RAMBlock *block;
+ ram_addr_t offset;
+ size_t used_len, start, npages;
From your use I think the addr and len are coming raw from the guest;
so we need to take some care.
Actually the "addr" here has been the host address that corresponds to
the guest free page. It's from elem->in_sg[0].iov_base.
+ if (unlikely(offset + len > block->used_length)) {
I think to make that overflow safe, that should be:
if (len > (block->used_length - offset)) {
But we'll need another test before it, because qemu_ram_block_from_host
seems to check max_length not used_length, so we need to check
for offset > block->used_length first
OK, how about adding an assert above, like this:
block = qemu_ram_block_from_host(addr, false, &offset);
assert (offset < block->used_length );
if (!block)
...
The address corresponds to a guest free page, which means it should be
within used_length. If not, something weird happens, I think we'd better
to assert it in that case.
Best,
Wei
