68 lines
2.6 KiB
Diff
68 lines
2.6 KiB
Diff
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From 2ffc49eea1bbd454913a88a0ad872c2649b36950 Mon Sep 17 00:00:00 2001
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From: David Hildenbrand <david@redhat.com>
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Date: Mon, 22 Jul 2019 15:41:05 +0200
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Subject: [PATCH] virtio-balloon: Simplify deflate with pbp
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Let's simplify this - the case we are optimizing for is very hard to
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trigger and not worth the effort. If we're switching from inflation to
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deflation, let's reset the pbp.
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Acked-by: David Gibson <david@gibson.dropbear.id.au>
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Signed-off-by: David Hildenbrand <david@redhat.com>
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Message-Id: <20190722134108.22151-4-david@redhat.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry-picked from commit 2ffc49eea1bbd454913a88a0ad872c2649b36950)
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---
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hw/virtio/virtio-balloon.c | 26 +++++---------------------
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1 file changed, 5 insertions(+), 21 deletions(-)
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diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
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index a78d2d2184..04a7e6c772 100644
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--- a/hw/virtio/virtio-balloon.c
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+++ b/hw/virtio/virtio-balloon.c
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@@ -117,7 +117,7 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
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void *addr = memory_region_get_ram_ptr(mr) + offset;
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RAMBlock *rb;
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size_t rb_page_size;
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- ram_addr_t ram_offset, host_page_base;
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+ ram_addr_t ram_offset;
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void *host_addr;
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int ret;
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@@ -125,27 +125,11 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
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* host address? */
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rb = qemu_ram_block_from_host(addr, false, &ram_offset);
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rb_page_size = qemu_ram_pagesize(rb);
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- host_page_base = ram_offset & ~(rb_page_size - 1);
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-
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- if (balloon->pbp
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- && rb == balloon->pbp->rb
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- && host_page_base == balloon->pbp->base) {
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- int subpages = rb_page_size / BALLOON_PAGE_SIZE;
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- /*
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- * This means the guest has asked to discard some of the 4kiB
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- * subpages of a host page, but then changed its mind and
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- * asked to keep them after all. It's exceedingly unlikely
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- * for a guest to do this in practice, but handle it anyway,
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- * since getting it wrong could mean discarding memory the
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- * guest is still using. */
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- clear_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
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- balloon->pbp->bitmap);
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-
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- if (bitmap_empty(balloon->pbp->bitmap, subpages)) {
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- g_free(balloon->pbp);
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- balloon->pbp = NULL;
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- }
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+ if (balloon->pbp) {
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+ /* Let's play safe and always reset the pbp on deflation requests. */
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+ g_free(balloon->pbp);
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+ balloon->pbp = NULL;
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}
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host_addr = (void *)((uintptr_t)addr & ~(rb_page_size - 1));
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--
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2.19.1
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