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>
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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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void *addr = memory_region_get_ram_ptr(mr) + offset;
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RAMBlock *rb;
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RAMBlock *rb;
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size_t rb_page_size;
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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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void *host_addr;
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int ret;
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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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* host address? */
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rb = qemu_ram_block_from_host(addr, false, &ram_offset);
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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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rb_page_size = qemu_ram_pagesize(rb);
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host_page_base = ram_offset & ~(rb_page_size - 1);
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if (balloon->pbp
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if (balloon->pbp) {
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&& rb == balloon->pbp->rb
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/* Let's play safe and always reset the pbp on deflation requests. */
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&& host_page_base == balloon->pbp->base) {
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g_free(balloon->pbp);
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int subpages = rb_page_size / BALLOON_PAGE_SIZE;
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balloon->pbp = NULL;
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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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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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}
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}
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host_addr = (void *)((uintptr_t)addr & ~(rb_page_size - 1));
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host_addr = (void *)((uintptr_t)addr & ~(rb_page_size - 1));
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