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authorDavid Hildenbrand <david@redhat.com>2019-07-22 15:41:05 +0200
committerMichael S. Tsirkin <mst@redhat.com>2019-07-25 07:57:56 -0400
commit2ffc49eea1bbd454913a88a0ad872c2649b36950 (patch)
treec911c3f2ec42dbd7078a64cea63d20fa1bf9dd42 /hw
parent483f13524bb2a08b7ff6a7560b846564ed3b0c33 (diff)
virtio-balloon: Simplify deflate with pbp
Let's simplify this - the case we are optimizing for is very hard to trigger and not worth the effort. If we're switching from inflation to deflation, let's reset the pbp. Acked-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: David Hildenbrand <david@redhat.com> Message-Id: <20190722134108.22151-4-david@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'hw')
-rw-r--r--hw/virtio/virtio-balloon.c26
1 files changed, 5 insertions, 21 deletions
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index a78d2d2184..04a7e6c772 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -117,7 +117,7 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
void *addr = memory_region_get_ram_ptr(mr) + offset;
RAMBlock *rb;
size_t rb_page_size;
- ram_addr_t ram_offset, host_page_base;
+ ram_addr_t ram_offset;
void *host_addr;
int ret;
@@ -125,27 +125,11 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
* host address? */
rb = qemu_ram_block_from_host(addr, false, &ram_offset);
rb_page_size = qemu_ram_pagesize(rb);
- host_page_base = ram_offset & ~(rb_page_size - 1);
-
- if (balloon->pbp
- && rb == balloon->pbp->rb
- && host_page_base == balloon->pbp->base) {
- int subpages = rb_page_size / BALLOON_PAGE_SIZE;
- /*
- * This means the guest has asked to discard some of the 4kiB
- * subpages of a host page, but then changed its mind and
- * asked to keep them after all. It's exceedingly unlikely
- * for a guest to do this in practice, but handle it anyway,
- * since getting it wrong could mean discarding memory the
- * guest is still using. */
- clear_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
- balloon->pbp->bitmap);
-
- if (bitmap_empty(balloon->pbp->bitmap, subpages)) {
- g_free(balloon->pbp);
- balloon->pbp = NULL;
- }
+ if (balloon->pbp) {
+ /* Let's play safe and always reset the pbp on deflation requests. */
+ g_free(balloon->pbp);
+ balloon->pbp = NULL;
}
host_addr = (void *)((uintptr_t)addr & ~(rb_page_size - 1));