From patchwork Thu Jul 25 11:36:34 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 1136869 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45vVYk3vwLz9sDQ for ; Thu, 25 Jul 2019 21:37:14 +1000 (AEST) Received: from localhost ([::1]:58850 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqc3c-0001kr-BF for incoming@patchwork.ozlabs.org; Thu, 25 Jul 2019 07:37:12 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51248) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqc3O-0001Sq-93 for qemu-devel@nongnu.org; Thu, 25 Jul 2019 07:36:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hqc3M-00038K-9B for qemu-devel@nongnu.org; Thu, 25 Jul 2019 07:36:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52770) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hqc3K-000379-Au; Thu, 25 Jul 2019 07:36:56 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 195E83092641; Thu, 25 Jul 2019 11:36:53 +0000 (UTC) Received: from t460s.redhat.com (ovpn-117-70.ams2.redhat.com [10.36.117.70]) by smtp.corp.redhat.com (Postfix) with ESMTP id 928DD5437A; Thu, 25 Jul 2019 11:36:51 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Date: Thu, 25 Jul 2019 13:36:34 +0200 Message-Id: <20190725113638.4702-4-david@redhat.com> In-Reply-To: <20190725113638.4702-1-david@redhat.com> References: <20190725113638.4702-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 25 Jul 2019 11:36:53 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH-for-4.1 v4 3/7] virtio-balloon: Simplify deflate with pbp X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Michael S . Tsirkin" , David Hildenbrand , qemu-stable@nongnu.org, Stefan Hajnoczi , Igor Mammedov , David Gibson Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" 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 Signed-off-by: David Hildenbrand --- hw/virtio/virtio-balloon.c | 26 +++++--------------------- 1 file 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));