From patchwork Thu Feb 14 04:39:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gibson X-Patchwork-Id: 10811791 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6FE91746 for ; Thu, 14 Feb 2019 04:44:11 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5E05428796 for ; Thu, 14 Feb 2019 04:44:11 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 507FA28B57; Thu, 14 Feb 2019 04:44:11 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id EA7C828796 for ; Thu, 14 Feb 2019 04:44:10 +0000 (UTC) Received: from localhost ([127.0.0.1]:39975 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8sc-0004AU-8a for patchwork-qemu-devel@patchwork.kernel.org; Wed, 13 Feb 2019 23:44:10 -0500 Received: from eggs.gnu.org ([209.51.188.92]:45973) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8p5-0002EK-6a for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gu8on-0006up-L7 for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:18 -0500 Received: from ozlabs.org ([2401:3900:2:1::2]:60135) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gu8oh-0006OU-2u; Wed, 13 Feb 2019 23:40:09 -0500 Received: by ozlabs.org (Postfix, from userid 1007) id 440Nvr19PMz9sMp; Thu, 14 Feb 2019 15:39:20 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1550119160; bh=B7BjmFE145e/oytYlbFVg2OL0vdT6WxWyxJuj/WEYEU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kz/kX8al1JcrlNOYEfi81kbCw1VPJ4158vmTiNKBOfFuS5bRZLPCmzj1MUVF2eo8Z qSRtMWFMqqS30GdFlIzvQEVIkZTc4VBJ3KkVusOnkrHFVjCkqbFKGy3pqI1FAU+Tvc WnDlzvXLPKtZk1lmkl2tQ54LpBzzRiHKBykYLoNs= From: David Gibson To: mst@redhat.com, qemu-devel@nongnu.org Date: Thu, 14 Feb 2019 15:39:12 +1100 Message-Id: <20190214043916.22128-2-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190214043916.22128-1-david@gibson.dropbear.id.au> References: <20190214043916.22128-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2401:3900:2:1::2 Subject: [Qemu-devel] [PATCH 1/5] virtio-balloon: Remove unnecessary MADV_WILLNEED on deflate X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP When the balloon is inflated, we discard memory place in it using madvise() with MADV_DONTNEED. And when we deflate it we use MADV_WILLNEED, which sounds like it makes sense but is actually unnecessary. The misleadingly named MADV_DONTNEED just discards the memory in question, it doesn't set any persistent state on it in-kernel; all that's necessary to bring the memory back is to touch it. MADV_WILLNEED in contrast specifically says that the memory will be used soon and faults it in. This patch simplify's the balloon operation by dropping the madvise() on deflate. This might have an impact on performance - it will move a delay at deflate time until that memory is actually touched, which might be more latency sensitive. However: * Memory that's being given back to the guest by deflating the balloon *might* be used soon, but it equally could just sit around in the guest's pools until needed (or even be faulted out again if the host is under memory pressure). * Usually, the timescale over which you'll be adjusting the balloon is long enough that a few extra faults after deflation aren't going to make a difference. Signed-off-by: David Gibson Reviewed-by: David Hildenbrand Reviewed-by: Michael S. Tsirkin --- hw/virtio/virtio-balloon.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index a12677d4d5..43af521884 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -35,9 +35,8 @@ static void balloon_page(void *addr, int deflate) { - if (!qemu_balloon_is_inhibited()) { - qemu_madvise(addr, BALLOON_PAGE_SIZE, - deflate ? QEMU_MADV_WILLNEED : QEMU_MADV_DONTNEED); + if (!qemu_balloon_is_inhibited() && !deflate) { + qemu_madvise(addr, BALLOON_PAGE_SIZE, QEMU_MADV_DONTNEED); } } From patchwork Thu Feb 14 04:39:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gibson X-Patchwork-Id: 10811787 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CBE5813A4 for ; Thu, 14 Feb 2019 04:43:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BA0B22DDAE for ; Thu, 14 Feb 2019 04:43:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AD01F2DDB4; Thu, 14 Feb 2019 04:43:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 4808D2DDAE for ; Thu, 14 Feb 2019 04:43:35 +0000 (UTC) Received: from localhost ([127.0.0.1]:39962 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8s2-0003dv-J1 for patchwork-qemu-devel@patchwork.kernel.org; Wed, 13 Feb 2019 23:43:34 -0500 Received: from eggs.gnu.org ([209.51.188.92]:46008) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8p7-0002GB-3q for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gu8os-0006ye-Mq for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:26 -0500 Received: from ozlabs.org ([2401:3900:2:1::2]:45415) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gu8oh-0006OW-2y; Wed, 13 Feb 2019 23:40:09 -0500 Received: by ozlabs.org (Postfix, from userid 1007) id 440Nvr1xbXz9sMx; Thu, 14 Feb 2019 15:39:20 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1550119160; bh=3/yOpaPIHgovVGzYhgaTIRb3gPBnbEomTVCzz6dAsNc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SjOrX1a4yAVLz5ZbgC+0+PNWx1ia96g6ikaz5SECMW9AdT7YJSOO0J+Hk9F3TiaXJ rqsP8zDJlNHZ3Sm9yimq8boNe8EE6M3KP5/qXPHmLILfvGdo6SbdaejguOVj65Az5F pxUC0DlqsQaK7PVVwwP1gJFT2u6lxK8VSJnkIiRY= From: David Gibson To: mst@redhat.com, qemu-devel@nongnu.org Date: Thu, 14 Feb 2019 15:39:13 +1100 Message-Id: <20190214043916.22128-3-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190214043916.22128-1-david@gibson.dropbear.id.au> References: <20190214043916.22128-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2401:3900:2:1::2 Subject: [Qemu-devel] [PATCH 2/5] virtio-balloon: Corrections to address verification X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP The virtio-balloon device's verification of the address given to it by the guest has a number of faults: * The addresses here are guest physical addresses, which should be 'hwaddr' rather than 'ram_addr_t' (the distinction is admittedly pretty subtle and confusing) * We don't check for section.mr being NULL, which is the main way that memory_region_find() reports basic failures. We really need to check that before looking at any other section fields, because memory_region_find() doesn't initialize them on the failure path * We're passing a length of '1' to memory_region_find(), but really the guest is requesting that we put the entire page into the balloon, so it makes more sense to call it with BALLOON_PAGE_SIZE Signed-off-by: David Gibson Reviewed-by: David Hildenbrand Reviewed-by: Michael S. Tsirkin Reviewed-by: Greg Kurz --- hw/virtio/virtio-balloon.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index 43af521884..eb357824d8 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -221,17 +221,20 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) } while (iov_to_buf(elem->out_sg, elem->out_num, offset, &pfn, 4) == 4) { - ram_addr_t pa; - ram_addr_t addr; + hwaddr pa; + hwaddr addr; int p = virtio_ldl_p(vdev, &pfn); - pa = (ram_addr_t) p << VIRTIO_BALLOON_PFN_SHIFT; + pa = (hwaddr) p << VIRTIO_BALLOON_PFN_SHIFT; offset += 4; - /* FIXME: remove get_system_memory(), but how? */ - section = memory_region_find(get_system_memory(), pa, 1); - if (!int128_nz(section.size) || - !memory_region_is_ram(section.mr) || + section = memory_region_find(get_system_memory(), pa, + BALLOON_PAGE_SIZE); + if (!section.mr) { + trace_virtio_balloon_bad_addr(pa); + continue; + } + if (!memory_region_is_ram(section.mr) || memory_region_is_rom(section.mr) || memory_region_is_romd(section.mr)) { trace_virtio_balloon_bad_addr(pa); From patchwork Thu Feb 14 04:39:14 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gibson X-Patchwork-Id: 10811767 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D0FEC746 for ; Thu, 14 Feb 2019 04:42:03 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BEE062DDA7 for ; Thu, 14 Feb 2019 04:42:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B208E2DDAE; Thu, 14 Feb 2019 04:42:03 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 4D9F82DDA7 for ; Thu, 14 Feb 2019 04:42:03 +0000 (UTC) Received: from localhost ([127.0.0.1]:39956 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8qY-0003VB-HL for patchwork-qemu-devel@patchwork.kernel.org; Wed, 13 Feb 2019 23:42:02 -0500 Received: from eggs.gnu.org ([209.51.188.92]:45970) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8p5-0002EF-6O for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gu8on-0006uh-JH for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:18 -0500 Received: from ozlabs.org ([2401:3900:2:1::2]:44773) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gu8oh-0006Oa-2k; Wed, 13 Feb 2019 23:40:09 -0500 Received: by ozlabs.org (Postfix, from userid 1007) id 440Nvr3rrZz9sN9; Thu, 14 Feb 2019 15:39:20 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1550119160; bh=xQXB7NXvyxO7J7letXN6DMuzfy/S7ZPsCKWOGoAEg1U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JAVO1F3As4f2+4ywyi6NgnSm6uALbJ56Amftp05AScyfcbmJDWkDVtE8s0M6YP3RM zQg8bgBdCeBmjyor0BVe94Bv6U3y4ps6Yx1CY/5nTJEMl+JTEOQF5CFSGiIMueRFSR q1PpEA4geWL0LkS8Q4ZDU0EPZK2o+9J2yytIVraI= From: David Gibson To: mst@redhat.com, qemu-devel@nongnu.org Date: Thu, 14 Feb 2019 15:39:14 +1100 Message-Id: <20190214043916.22128-4-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190214043916.22128-1-david@gibson.dropbear.id.au> References: <20190214043916.22128-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2401:3900:2:1::2 Subject: [Qemu-devel] [PATCH 3/5] virtio-balloon: Rework ballon_page() interface X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP This replaces the balloon_page() internal interface with ballon_inflate_page(), with a slightly different interface. The new interface will make future alterations simpler. Signed-off-by: David Gibson Reviewed-by: David Hildenbrand Reviewed-by: Michael S. Tsirkin --- hw/virtio/virtio-balloon.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index eb357824d8..bf93148486 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -33,11 +33,12 @@ #define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT) -static void balloon_page(void *addr, int deflate) +static void balloon_inflate_page(VirtIOBalloon *balloon, + MemoryRegion *mr, hwaddr offset) { - if (!qemu_balloon_is_inhibited() && !deflate) { - qemu_madvise(addr, BALLOON_PAGE_SIZE, QEMU_MADV_DONTNEED); - } + void *addr = memory_region_get_ram_ptr(mr) + offset; + + qemu_madvise(addr, BALLOON_PAGE_SIZE, QEMU_MADV_DONTNEED); } static const char *balloon_stat_names[] = { @@ -222,7 +223,6 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) while (iov_to_buf(elem->out_sg, elem->out_num, offset, &pfn, 4) == 4) { hwaddr pa; - hwaddr addr; int p = virtio_ldl_p(vdev, &pfn); pa = (hwaddr) p << VIRTIO_BALLOON_PFN_SHIFT; @@ -244,11 +244,9 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) trace_virtio_balloon_handle_output(memory_region_name(section.mr), pa); - /* Using memory_region_get_ram_ptr is bending the rules a bit, but - should be OK because we only want a single page. */ - addr = section.offset_within_region; - balloon_page(memory_region_get_ram_ptr(section.mr) + addr, - !!(vq == s->dvq)); + if (!qemu_balloon_is_inhibited() && vq != s->dvq) { + balloon_inflate_page(s, section.mr, section.offset_within_region); + } memory_region_unref(section.mr); } From patchwork Thu Feb 14 04:39:15 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gibson X-Patchwork-Id: 10811793 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 67F436C2 for ; Thu, 14 Feb 2019 04:46:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5117B2DC29 for ; Thu, 14 Feb 2019 04:46:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4566F2DCCB; Thu, 14 Feb 2019 04:46:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id CA0642DC29 for ; Thu, 14 Feb 2019 04:46:01 +0000 (UTC) Received: from localhost ([127.0.0.1]:40038 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8uO-0006fz-JO for patchwork-qemu-devel@patchwork.kernel.org; Wed, 13 Feb 2019 23:46:00 -0500 Received: from eggs.gnu.org ([209.51.188.92]:46007) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8p7-0002G8-3M for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gu8os-0006yt-OW for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:26 -0500 Received: from ozlabs.org ([2401:3900:2:1::2]:53275) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gu8oh-0006OY-2l; Wed, 13 Feb 2019 23:40:09 -0500 Received: by ozlabs.org (Postfix, from userid 1007) id 440Nvr395Nz9sN4; Thu, 14 Feb 2019 15:39:20 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1550119160; bh=nWRdTR7bVRlVF/K07KuGeCKDx4BJXMraKKIyCPjHuuY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hmE5Mm6rI2JRUhQ2ZUUNV7Z4/l9QXW9sPvLzSrsxDVmeVQ8pBzpdTJjCYIaxIXQpk DqnMfHDv0Xhcdrrd4TDQa2m8DZRo3xKR3vyfwmTeMCxtLav6ZLVdbgc6deFnpxQDVV NoDu5VjCThcMkyl44C7YqrRLvKDXPaP3zRfzoScw= From: David Gibson To: mst@redhat.com, qemu-devel@nongnu.org Date: Thu, 14 Feb 2019 15:39:15 +1100 Message-Id: <20190214043916.22128-5-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190214043916.22128-1-david@gibson.dropbear.id.au> References: <20190214043916.22128-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2401:3900:2:1::2 Subject: [Qemu-devel] [PATCH 4/5] virtio-balloon: Use ram_block_discard_range() instead of raw madvise() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Currently, virtio-balloon uses madvise() with MADV_DONTNEED to actually discard RAM pages inserted into the balloon. This is basically a Linux only interface (MADV_DONTNEED exists on some other platforms, but doesn't always have the same semantics). It also doesn't work on hugepages and has some other limitations. It turns out that postcopy also needs to discard chunks of memory, and uses a better interface for it: ram_block_discard_range(). It doesn't cover every case, but it covers more than going direct to madvise() and this gives us a single place to update for more possibilities in future. There are some subtleties here to maintain the current balloon behaviour: * For now, we just ignore requests to balloon in a hugepage backed region. That matches current behaviour, because MADV_DONTNEED on a hugepage would simply fail, and we ignore the error. * If host page size is > BALLOON_PAGE_SIZE we can frequently call this on non-host-page-aligned addresses. These would also fail in madvise(), which we then ignored. ram_block_discard_range() error_report()s calls on unaligned addresses, so we explicitly check that case to avoid spamming the logs. * We now call ram_block_discard_range() with the *host* page size, whereas we previously called madvise() with BALLOON_PAGE_SIZE. Surprisingly, this also matches existing behaviour. Although the kernel fails madvise on unaligned addresses, it will round unaligned sizes *up* to the host page size. Yes, this means that if BALLOON_PAGE_SIZE < guest page size we can incorrectly discard more memory than the guest asked us to. I'm planning to address that soon. Errors other than the ones discussed above, will now be reported by ram_block_discard_range(), rather than silently ignored, which means we have a much better chance of seeing when something is going wrong. Signed-off-by: David Gibson Reviewed-by: Michael S. Tsirkin --- hw/virtio/virtio-balloon.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index bf93148486..e4cd8d566b 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -37,8 +37,29 @@ static void balloon_inflate_page(VirtIOBalloon *balloon, MemoryRegion *mr, hwaddr offset) { void *addr = memory_region_get_ram_ptr(mr) + offset; + RAMBlock *rb; + size_t rb_page_size; + ram_addr_t ram_offset; - qemu_madvise(addr, BALLOON_PAGE_SIZE, QEMU_MADV_DONTNEED); + /* XXX is there a better way to get to the RAMBlock than via a + * host address? */ + rb = qemu_ram_block_from_host(addr, false, &ram_offset); + rb_page_size = qemu_ram_pagesize(rb); + + /* Silently ignore hugepage RAM blocks */ + if (rb_page_size != getpagesize()) { + return; + } + + /* Silently ignore unaligned requests */ + if (ram_offset & (rb_page_size - 1)) { + return; + } + + ram_block_discard_range(rb, ram_offset, rb_page_size); + /* We ignore errors from ram_block_discard_range(), because it has + * already reported them, and failing to discard a balloon page is + * not fatal */ } static const char *balloon_stat_names[] = { From patchwork Thu Feb 14 04:39:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gibson X-Patchwork-Id: 10811795 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 996576C2 for ; Thu, 14 Feb 2019 04:46:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8443A2DC15 for ; Thu, 14 Feb 2019 04:46:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 736EA2DC87; Thu, 14 Feb 2019 04:46:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id CA4312DC15 for ; Thu, 14 Feb 2019 04:46:44 +0000 (UTC) Received: from localhost ([127.0.0.1]:40040 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8v6-00077K-5r for patchwork-qemu-devel@patchwork.kernel.org; Wed, 13 Feb 2019 23:46:44 -0500 Received: from eggs.gnu.org ([209.51.188.92]:46354) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gu8pS-0002YX-B2 for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gu8pE-0007CR-UL for qemu-devel@nongnu.org; Wed, 13 Feb 2019 23:40:48 -0500 Received: from ozlabs.org ([2401:3900:2:1::2]:40795) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gu8pE-0006v3-0a; Wed, 13 Feb 2019 23:40:40 -0500 Received: by ozlabs.org (Postfix, from userid 1007) id 440Nvr4ctfz9sN8; Thu, 14 Feb 2019 15:39:20 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1550119160; bh=2Lp42hE+I2N0ishsTEnbN0moixP3X2aGKuoJOni2jo8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dbHESOD7+BjcS5V0pULYmGFceRscyKKXTamyspACdvwzOVfbc0lW6XngR3OOpEHdz HZ1ludrrk4F2WxwrIWuCI7dQ7hVCcLyck36KsvNoi6ylmtkv25Eq1jSXe5xC5GJ0HZ rZeo72slcAa6zsSV/DekdH72ZWG6yYsT/TRKgASU= From: David Gibson To: mst@redhat.com, qemu-devel@nongnu.org Date: Thu, 14 Feb 2019 15:39:16 +1100 Message-Id: <20190214043916.22128-6-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190214043916.22128-1-david@gibson.dropbear.id.au> References: <20190214043916.22128-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2401:3900:2:1::2 Subject: [Qemu-devel] [PATCH 5/5] virtio-balloon: Safely handle BALLOON_PAGE_SIZE < host page size X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP The virtio-balloon always works in units of 4kiB (BALLOON_PAGE_SIZE), but we can only actually discard memory in units of the host page size. Now, we handle this very badly: we silently ignore balloon requests that aren't host page aligned, and for requests that are host page aligned we discard the entire host page. The latter can corrupt guest memory if its page size is smaller than the host's. The obvious choice would be to disable the balloon if the host page size is not 4kiB. However, that would break the special case where host and guest have the same page size, but that's larger than 4kiB. That case currently works by accident[1] - and is used in practice on many production POWER systems where 64kiB has long been the Linux default page size on both host and guest. To make the balloon safe, without breaking that useful special case, we need to accumulate 4kiB balloon requests until we have a whole contiguous host page to discard. We could in principle do that across all guest memory, but it would require a large bitmap to track. This patch represents a compromise: we track ballooned subpages for a single contiguous host page at a time. This means that if the guest discards all 4kiB chunks of a host page in succession, we will discard it. This is the expected behaviour in the (host page) == (guest page) != 4kiB case we want to support. If the guest scatters 4kiB requests across different host pages, we don't discard anything, and issue a warning. Not ideal, but at least we don't corrupt guest memory as the previous version could. Warning reporting is kind of a compromise here. Determining whether we're in a problematic state at realize() time is tricky, because we'd have to look at the host pagesizes of all memory backends, but we can't really know if some of those backends could be for special purpose memory that's not subject to ballooning. Reporting only when the guest tries to balloon a partial page also isn't great because if the guest page size happens to line up it won't indicate that we're in a non ideal situation. It could also cause alarming repeated warnings whenever a migration is attempted. So, what we do is warn the first time the guest attempts balloon a partial host page, whether or not it will end up ballooning the rest of the page immediately afterwards. [1] Because when the guest attempts to balloon a page, it will submit requests for each 4kiB subpage. Most will be ignored, but the one which happens to be host page aligned will discard the whole lot. Signed-off-by: David Gibson --- hw/virtio/virtio-balloon.c | 69 +++++++++++++++++++++++++----- include/hw/virtio/virtio-balloon.h | 3 ++ 2 files changed, 62 insertions(+), 10 deletions(-) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index e4cd8d566b..65f861cbef 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -33,33 +33,82 @@ #define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT) +typedef struct PartiallyBalloonedPage { + RAMBlock *rb; + ram_addr_t base; + unsigned long bitmap[]; +} PartiallyBalloonedPage; + static void balloon_inflate_page(VirtIOBalloon *balloon, MemoryRegion *mr, hwaddr offset) { void *addr = memory_region_get_ram_ptr(mr) + offset; RAMBlock *rb; size_t rb_page_size; - ram_addr_t ram_offset; + int subpages; + ram_addr_t ram_offset, host_page_base; /* XXX is there a better way to get to the RAMBlock than via a * 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 (rb_page_size == BALLOON_PAGE_SIZE) { + /* Easy case */ - /* Silently ignore hugepage RAM blocks */ - if (rb_page_size != getpagesize()) { + ram_block_discard_range(rb, ram_offset, rb_page_size); + /* We ignore errors from ram_block_discard_range(), because it + * has already reported them, and failing to discard a balloon + * page is not fatal */ return; } - /* Silently ignore unaligned requests */ - if (ram_offset & (rb_page_size - 1)) { - return; + /* Hard case + * + * We've put a piece of a larger host page into the balloon - we + * need to keep track until we have a whole host page to + * discard + */ + warn_report_once( +"Balloon used with backing page size > 4kiB, this may not be reliable"); + + subpages = rb_page_size / BALLOON_PAGE_SIZE; + + if (balloon->pbp + && (rb != balloon->pbp->rb + || host_page_base != balloon->pbp->base)) { + /* We've partially ballooned part of a host page, but now + * we're trying to balloon part of a different one. Too hard, + * give up on the old partial page */ + free(balloon->pbp); + balloon->pbp = NULL; } - ram_block_discard_range(rb, ram_offset, rb_page_size); - /* We ignore errors from ram_block_discard_range(), because it has - * already reported them, and failing to discard a balloon page is - * not fatal */ + if (!balloon->pbp) { + /* Starting on a new host page */ + size_t bitlen = BITS_TO_LONGS(subpages) * sizeof(unsigned long); + balloon->pbp = g_malloc0(sizeof(PartiallyBalloonedPage) + bitlen); + balloon->pbp->rb = rb; + balloon->pbp->base = host_page_base; + } + + bitmap_set(balloon->pbp->bitmap, + (ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, + subpages); + + if (bitmap_full(balloon->pbp->bitmap, subpages)) { + /* We've accumulated a full host page, we can actually discard + * it now */ + + ram_block_discard_range(rb, balloon->pbp->base, rb_page_size); + /* We ignore errors from ram_block_discard_range(), because it + * has already reported them, and failing to discard a balloon + * page is not fatal */ + + free(balloon->pbp); + balloon->pbp = NULL; + } } static const char *balloon_stat_names[] = { diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h index e0df3528c8..99dcd6d105 100644 --- a/include/hw/virtio/virtio-balloon.h +++ b/include/hw/virtio/virtio-balloon.h @@ -30,6 +30,8 @@ typedef struct virtio_balloon_stat_modern { uint64_t val; } VirtIOBalloonStatModern; +typedef struct PartiallyBalloonedPage PartiallyBalloonedPage; + typedef struct VirtIOBalloon { VirtIODevice parent_obj; VirtQueue *ivq, *dvq, *svq; @@ -42,6 +44,7 @@ typedef struct VirtIOBalloon { int64_t stats_last_update; int64_t stats_poll_interval; uint32_t host_features; + PartiallyBalloonedPage *pbp; } VirtIOBalloon; #endif