From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4A0D4CD4F21 for ; Tue, 12 May 2026 21:07:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B53F16B00D2; Tue, 12 May 2026 17:07:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B2BB96B00D4; Tue, 12 May 2026 17:07:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A40F36B00D5; Tue, 12 May 2026 17:07:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 92DF06B00D2 for ; Tue, 12 May 2026 17:07:57 -0400 (EDT) Received: from smtpin15.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 6A672140301 for ; Tue, 12 May 2026 21:07:57 +0000 (UTC) X-FDA: 84760004994.15.BDDED53 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 2BF2320007 for ; Tue, 12 May 2026 21:07:55 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=B1LIfdjj; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of mst@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=mst@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778620075; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=M5u/iM8du1/MGgA4/nGZcoKT5QLcOlAuJz0gbPaxdLE=; b=4SJOtjbcmIXIf6PTvxpwfwkncxxmCnB9W/EAumlT9dRI8y9ei276N+CuoMz1jnLpoI72SL 8Up5LU2JbGo0xN1y6qDsLspBe8QYCHjiAliK+3x9yguQ6ILelcmwxa64MRyfzATjjIsT2g /srAhDCo70bYNTgg+oePCvsAWzd34mw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778620075; a=rsa-sha256; cv=none; b=VRdrX+KO2Lyz4juM1Bsv5HgvlD0zLdkkzwGGWU09MqlTXyQaZOam6rEORmpM1j+Tyk4XgF KoRxjPUImCTrupw7P7lRlulJkP32YBdmX87zfFsdEt6iYle4l5Ukw+48ZJEGikWrtdaROG gmw5T/WMUlfsgOAmNxcx1Dc8eu3XYfk= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=B1LIfdjj; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of mst@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=mst@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1778620074; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=M5u/iM8du1/MGgA4/nGZcoKT5QLcOlAuJz0gbPaxdLE=; b=B1LIfdjjh3Dejup3jXLerFwKvsWhrRg2tLHgVNTvYRAtW0FJ6TPWLPvBNuaS5VPByxOyyo IZE7fnkRaC1+C2XFtfSaWWDCA6q74dAgeZV8/QwoU/ks0QMq82ESCP56n79cK+0c1768OG sAueehFW70HHdSqx6gQ9ZnoA5PQEUfM= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-88-iHu2lp6pOLO9Wfc7vIvfFQ-1; Tue, 12 May 2026 17:07:53 -0400 X-MC-Unique: iHu2lp6pOLO9Wfc7vIvfFQ-1 X-Mimecast-MFC-AGG-ID: iHu2lp6pOLO9Wfc7vIvfFQ_1778620072 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-488bd1ee9e7so65886625e9.1 for ; Tue, 12 May 2026 14:07:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778620072; x=1779224872; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=M5u/iM8du1/MGgA4/nGZcoKT5QLcOlAuJz0gbPaxdLE=; b=mltUQNuxKaJgG3dzW+8yDVvI1q2TLdctiZrabqagkz26QQbN1nSGeLXvW6F2kyKOMp GdSEOeROi7BysXprHLleaDJVCn5cU0GAegAdTiy27LSKyOZrR25iTVwAwpP53yd7LOHX VkFctG4bu1+8CuRXlQDniR4CqX9Z9MWbW763OWgKAwOo8ia26EXhrFbpH2d0j+ic02PY 67EUvRKPkaKzTVdo9nLX74gB5NW/4q2S+2WEwxcUV06QqnmjV6JRuV/LGMpCJsHmZ2tO EXgdvjPMHTd1JZXsi9IOv7ubdWaCnlEblru2ymAk1fNRpRYI6s6ZqZMPaTTKp5PT/khn k+mg== X-Forwarded-Encrypted: i=1; AFNElJ8jEqW4blZqOS58NWOZSMOyWSTGuLQ77nHmteP4wOl8/UH0Y1cRRm31+UT3Q/Dx8fl/3OOvfWCgzg==@kvack.org X-Gm-Message-State: AOJu0Yyeg6tx+EsvE4mn9ysClYBp3P1PX9DRKjZ+j0oGX0Y94hGHjtSY RIuPp1efMs6TRh6ePQe/Gwp86JoL37karDX6Zbq41DaH1THrDAH0uhfIe3xEv7U2NrfXVP3mDKm XURamq0AWIc1fbWt8ggHCi9BEph8jrlNyJhSiYgXQk1MnDV1zDKhG X-Gm-Gg: Acq92OHvAGVYFaIlqg7IzAuMkJ1fmsuHAZAt7lzGr/nJWAvcNLd7SE/Arty3Q4rae/D 1vzx2SwzktCaY6ba2Venh6Fo65zoL4nuiG7a6eGDNCuQDDh85NrnqJVr5Q0ITKxrHsypFtj4N+E 1pfCo6t0dSZSCOmX+Hi8/7BDuib8PGBtdIzc8iPs9xTEVh328NenrEAqlGS1zoQ8dDL+EwJ4p36 kemrSHAg7kNo/vZfjH9YEbzulUKo15iuVEhZNNT7ELgDck7bUjHAfBXmyWtSWpHpWpGb7bMQiCr TAUwiTxtVnQAKFl8MFsvcs0zhwsY7QltNDl/TtpcovMliSiA+vFxAAliqAXfKXQh7jc8xc/Nk+y lmuFQQbJ5MdbFN/1C3KaTFT4X8U2fUlGOHMJyrfEe X-Received: by 2002:a05:600c:c08e:b0:48a:5574:3a5b with SMTP id 5b1f17b1804b1-48fc9a5350bmr4617535e9.27.1778620072001; Tue, 12 May 2026 14:07:52 -0700 (PDT) X-Received: by 2002:a05:600c:c08e:b0:48a:5574:3a5b with SMTP id 5b1f17b1804b1-48fc9a5350bmr4617055e9.27.1778620071492; Tue, 12 May 2026 14:07:51 -0700 (PDT) Received: from redhat.com (IGLD-80-230-48-7.inter.net.il. [80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4548e4bbebdsm38944373f8f.5.2026.05.12.14.07.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 14:07:51 -0700 (PDT) Date: Tue, 12 May 2026 17:07:46 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: [PATCH v7 30/31] virtio_balloon: implement VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE Message-ID: <3b2729a80c19e634f9bc93ca2a8baed8cd760b45.1778616612.git.mst@redhat.com> References: MIME-Version: 1.0 In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: zPpqSj_kmx84SGflLdC33Ng0zqsgV5-h25kLiUVbtpo_1778620072 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Queue-Id: 2BF2320007 X-Rspamd-Server: rspam04 X-Stat-Signature: oz6byi8ruo55ppmetk3pmwmftaxz1s5q X-HE-Tag: 1778620075-144422 X-HE-Meta: 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 SQlaHMRG OhdvpyFKFO3paEWjaKdMEKVn8gxwiueY9k1eqSfk79Ev/jDdHEcIMkqTgTQ8oUW4kSFREyFlr7zpWfaZDAt2y/KOsGqfl9h2MJ3RFd8fDS1R8sldTuBKK8CkIY7aA1VOZSmOTcHYubJIBH8t5Dff7xVyNC/jlJ85+cfNxs7TnSCbdtJj86cVuYTk/hh0++TphvzyPBVtrqukSkJuSn20S5gVYa5Vp03GfSNEVnf4M9Ibnx0AhgiyXEok8h+82fAK2GwArR/Up5ZFlets8c8rM1hcd2wLmky5n9xcrG3nLlEN0vknf3CFO22j103KMpaT9UoO3xriPmqFakQsJJSIqX5I7B+8h8gDtgA5r2mylgw/eBqJvvC5h9kpYx4Id6wmyud64hdrQ07qAjzv67kPGxODYzOvj7VhJtP3jtBa4scGztmr8w1+2FoJmFYXIFqp4CnvcDlvuPQPXNPHhnN6g3HBY4A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When the device offers DEVICE_INIT_ON_INFLATE (bit 7), the device initializes inflated pages and returns a per-page bitmap indicating which pages were successfully initialized. The driver appends a device-writable bitmap buffer to each inflate descriptor chain via virtqueue_add_sgs. After the host acknowledges, the driver checks bitmap bits (bounded by used_len) and marks pages with SetPageZeroed. tell_host() returns used_len from virtqueue_get_buf(). Bitmap reads are bounded: fill_balloon() and virtballoon_migratepage() only trust bits within the used_len range. On deflate, release_pages_balloon checks PageZeroed per page and uses put_page_zeroed for pages the host initialized, propagating the zeroed hint to the buddy allocator. If inflate_vq has fewer than 2 descriptors, probe fails with -ENOSPC. If PAGE_POISON is negotiated with non-zero poison_val, the feature is cleared in validate(). See the virtio spec change: https://lore.kernel.org/all/9c69b992c3dd83dfef3db92cd86b2fd8a0730d48.1777731396.git.mst@redhat.com Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- drivers/virtio/virtio_balloon.c | 102 ++++++++++++++++++++++++---- include/uapi/linux/virtio_balloon.h | 1 + 2 files changed, 90 insertions(+), 13 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 02d21147d4c6..f3929a238c8b 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -121,6 +121,9 @@ struct virtio_balloon { struct virtqueue *reporting_vq; struct page_reporting_dev_info pr_dev_info; + /* Bitmap returned by host for DEVICE_INIT_ON_INFLATE */ + DECLARE_BITMAP(inflate_bitmap, VIRTIO_BALLOON_ARRAY_PFNS_MAX); + /* State for keeping the wakeup_source active while adjusting the balloon */ spinlock_t wakeup_lock; bool processing_wakeup_event; @@ -181,20 +184,30 @@ static void balloon_ack(struct virtqueue *vq) wake_up(&vb->acked); } -static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) +static unsigned int tell_host(struct virtio_balloon *vb, struct virtqueue *vq) { - struct scatterlist sg; + struct scatterlist sg_out, sg_in; + struct scatterlist *sgs[] = { &sg_out, &sg_in }; unsigned int len; - sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); + sg_init_one(&sg_out, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); - /* We should always be able to add one buffer to an empty queue. */ - virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); + if (vq == vb->inflate_vq && + virtio_has_feature(vb->vdev, + VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE)) { + unsigned int bitmap_bytes; + + bitmap_bytes = DIV_ROUND_UP(vb->num_pfns, 8); + bitmap_zero(vb->inflate_bitmap, vb->num_pfns); + sg_init_one(&sg_in, vb->inflate_bitmap, bitmap_bytes); + virtqueue_add_sgs(vq, sgs, 1, 1, vb, GFP_KERNEL); + } else { + virtqueue_add_outbuf(vq, &sg_out, 1, vb, GFP_KERNEL); + } virtqueue_kick(vq); - /* When host has read buffer, this completes via balloon_ack */ wait_event(vb->acked, virtqueue_get_buf(vq, &len)); - + return len; } static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, @@ -297,8 +310,37 @@ static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num) num_allocated_pages = vb->num_pfns; /* Did we get any? */ - if (vb->num_pfns != 0) - tell_host(vb, vb->inflate_vq); + if (vb->num_pfns != 0) { + unsigned int used_len = tell_host(vb, vb->inflate_vq); + + if (virtio_has_feature(vb->vdev, + VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE)) { + unsigned int i; + unsigned int valid_bits = used_len * 8; + + for (i = 0; i < vb->num_pfns; + i += VIRTIO_BALLOON_PAGES_PER_PAGE) { + unsigned int pfn, j; + bool zeroed = true; + + if (i + VIRTIO_BALLOON_PAGES_PER_PAGE > valid_bits) + break; + for (j = 0; j < VIRTIO_BALLOON_PAGES_PER_PAGE; j++) { + if (!test_bit(i + j, vb->inflate_bitmap)) { + zeroed = false; + break; + } + } + if (zeroed) { + pfn = virtio32_to_cpu(vb->vdev, + vb->pfns[i]); + __SetPageZeroed(pfn_to_page(pfn >> + (PAGE_SHIFT - + VIRTIO_BALLOON_PFN_SHIFT))); + } + } + } + } mutex_unlock(&vb->balloon_lock); return num_allocated_pages; @@ -311,7 +353,12 @@ static void release_pages_balloon(struct virtio_balloon *vb, list_for_each_entry_safe(page, next, pages, lru) { list_del(&page->lru); - put_page(page); /* balloon reference */ + if (PageZeroed(page)) { + __ClearPageZeroed(page); + put_page_zeroed(page); + } else { + put_page(page); + } } } @@ -858,7 +905,25 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, /* balloon's page migration 1st step -- inflate "newpage" */ vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; set_page_pfns(vb, vb->pfns, newpage); - tell_host(vb, vb->inflate_vq); + { + unsigned int used_len = tell_host(vb, vb->inflate_vq); + + if (virtio_has_feature(vb->vdev, + VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE) && + used_len >= DIV_ROUND_UP(VIRTIO_BALLOON_PAGES_PER_PAGE, 8)) { + unsigned int j; + bool zeroed = true; + + for (j = 0; j < VIRTIO_BALLOON_PAGES_PER_PAGE; j++) { + if (!test_bit(j, vb->inflate_bitmap)) { + zeroed = false; + break; + } + } + if (zeroed) + __SetPageZeroed(newpage); + } + } /* balloon's page migration 2nd step -- deflate "page" */ vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; @@ -963,6 +1028,12 @@ static int virtballoon_probe(struct virtio_device *vdev) if (err) goto out_free_vb; + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE) && + virtqueue_get_vring_size(vb->inflate_vq) < 2) { + err = -ENOSPC; + goto out_del_vqs; + } + if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) vb->vb_dev_info.adjust_managed_page_count = true; #ifdef CONFIG_BALLOON_MIGRATION @@ -1188,11 +1259,15 @@ static int virtballoon_validate(struct virtio_device *vdev) /* Device fills with poison_val, not zeros; disable zeroed hint */ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON) && - !want_init_on_free()) + !want_init_on_free()) { __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_REPORTED); + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE); + } - if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) + if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) { __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_REPORTED); + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE); + } __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM); return 0; } @@ -1205,6 +1280,7 @@ static unsigned int features[] = { VIRTIO_BALLOON_F_PAGE_POISON, VIRTIO_BALLOON_F_REPORTING, VIRTIO_BALLOON_F_DEVICE_INIT_REPORTED, + VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE, }; static struct virtio_driver virtio_balloon_driver = { diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h index 13074631f300..cbaf18e0b17c 100644 --- a/include/uapi/linux/virtio_balloon.h +++ b/include/uapi/linux/virtio_balloon.h @@ -38,6 +38,7 @@ #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */ #define VIRTIO_BALLOON_F_REPORTING 5 /* Page reporting virtqueue */ #define VIRTIO_BALLOON_F_DEVICE_INIT_REPORTED 6 /* Device initializes reported pages */ +#define VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE 7 /* Device initializes pages on inflate */ /* Size of a PFN in the balloon interface. */ #define VIRTIO_BALLOON_PFN_SHIFT 12 -- MST