From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=170.10.133.124 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793093723; b=TAHtMPR9zFNe3ylnNgEKzyqMX7U+Ox7r6msZHLxhNQAm/+TCBPZW7kumVaoX8SVogh2t bN5K6HLBHwKtVs7JyI5RGH1g5ArcR1XZYCzf3djlHGIkex/51tU6EAp1gcKChd7WuenPv 7cWKJcICtI27AjNLDwtdRTAlXj8HEXgZqlyW0WOD/F9Zk2GgddyAwLbaFkyfmAfEa37KE eiJeg+EWZmo/OlC/N5HOD01DTc0qjyR5j1PsoCbSQOzYEkv4vta6orSbtXDAqujdf4B1D lBwVOnAOavv2THuwY0VXIOl3nR+S2BOEtJ7C1wgI0xRBGqGh0vYNBwGe+Xz/AdA6w7w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793093723; h=DMARC-Filter:DKIM-Signature:Received:X-MC-Unique: X-Mimecast-MFC-AGG-ID:Received:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received: X-Received:Received:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:In-Reply-To:X-Mimecast-Spam-Score:X-Mimecast-MFC-PROC-ID: X-Mimecast-Originator:Content-Type:Content-Disposition; bh=HWF1Lm9IEVGMMtM+ZXrfgWJyZeU0J8NTR2mjYrY1U18=; b=2v9RKkkeBTviodBX0lk21e/FXit0cKLKLOMAD8gWZEvf5cFtNJ+HQJFHNAyXxLCefv1E DIxlL2JxZtxGRU+ih0HGwKJCKhV6GPyHVRYLdR+25lKzTH2Rqzvw/RuEnyQPSn4ksI9S/ UWx+1Bf/MyVFUNjVTyzyxy/ohaLrwlSv5odK7RtKh6OOxP8BCaQJjXYwz+sgA/qP8VCtD JzeYVjTu/WPjw6/mhQx4ImUQohAliJ+sl1JmOMbd/jq7usc7zrAIrFnui2o0bKh7Ccr9Q Kp2xZab0FXDQBTMybibNm4jEe2kxsffiIB8+6vgYtN+4FiNvADeUj9bP+2xT/Ey6Djw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=AcTRJcYQ; arc=none smtp.remote-ip=170.10.133.124 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 715DB606A335 for ; Tue, 27 Oct 2026 09:35:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 715DB606A335 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=AcTRJcYQ DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1793093721; 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=HWF1Lm9IEVGMMtM+ZXrfgWJyZeU0J8NTR2mjYrY1U18=; b=AcTRJcYQqTbIs2yqyDHDO92o/i+cYH61RdHezJ4L4n0NJxzAWqytwCfMb5LBoXATNSnsV0 ymw2Kp6Pwy/Nooimh+VMwlq6qD0kTG7LdZwSbohGTMdOkLtmr6F5MtgHB5JDi/JSvVRjfZ roGnSqvJUI6vzvIjtTVoDTp5Kg7QBSc= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-510-lKY-NpYgMNar4DmZEY96wQ-1; Tue, 27 Oct 2026 05:35:20 -0400 X-MC-Unique: lKY-NpYgMNar4DmZEY96wQ-1 X-Mimecast-MFC-AGG-ID: lKY-NpYgMNar4DmZEY96wQ_1793093719 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4a4af69e06fso17221885e9.2 for ; Tue, 27 Oct 2026 02:35:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793093719; x=1793698519; h=in-reply-to:content-disposition:content-type: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 :content-type; bh=HWF1Lm9IEVGMMtM+ZXrfgWJyZeU0J8NTR2mjYrY1U18=; b=rx87lbHRpo/0Md9YyENZFyaA6dBmL3zpUzkR96Nds1WJNpKI5dm0EMCRalqc60Gk2d YFv2I4WyzuQOjfUxhjVGDtzb+owXM9h6hVVUarPKter6s9S6hDzNu8s3T7rMp5z4aBeF O7TsfsCLTB15lsODz8NAmQoFF43356RxK96Cq9WT0DzzqaQBm3XsxQxT6Ffd0e/3sNKf VJ3XixT4Ti+HCPJ7ItCfbkDkW6AyRCJhluyq6D+r77gSkhvhMcoYWvK2OcqRQ6kfYjqr DmL4DnvVS+kaJ5JPMBg5nFuLS5aZuaDMOlVRBL+kq5VT4rtd6b9AefN1vj+O82wWlJyc EO/A== X-Forwarded-Encrypted: i=1; AKwUvBwkSBG5d4mHJ+J+6B4lo5fadmjLwxH9jXPwJSqNnnxBVKsxExLQkXVIyN8WWWwsx+J0X3fO27hh0ygsRCnuxg==@lists.linux.dev X-Gm-Message-State: AFq9FYLcXPFqBifNUKf70T9ZWzbx2m+aKpxQtbWkzWDfIbSaTUlcXl8i ReEQJ4sr8synQZN1KFczRrjPeOSqiSTqfq7+dunhpZhha9cOh01iaLFYzIqnw45U4EmY7OHSEIm qC3Ayad3iUQfmt7wPgX5YHKfdQrIo4mzp39f6BjrGqGYO0re8DldoaLKwitF5E3AxUr6Z X-Gm-Gg: AYBFou0wzDtu2AhiXtUoM4kdWoujWfYM9ryCiezgRECrkfGPxrFDtoFiFh8e2TjHMGm YQVArWbDSckdGoTbGqXzQ0rYwPtB+NHCQshTsf8S+3c+tb9FJcQBk0pkuSraOdTFfC2TXaKhfQs MIbeNIWd/7nKU/T8YBTq7qpN3MQ366iE40UMfgxsRbsBZj7xl2TpiplUlZoQFnost+bKvzzUO4J iba4rjrcgD9vU01nIesybOgY6t9VNID9+Ag8fMs9VTQvL40saHthUechsPn0aw33yQuOms6fwae ZsIrNa24YNp2MOVpk+qEHnlabLZjwuBKc3p/0JDYiW6iFqskB5DXIOfh4fbqmX7vww0= X-Received: by 2002:a05:600c:c107:b0:4a5:e6fd:65e5 with SMTP id 5b1f17b1804b1-4a5e70ca839mr85162625e9.31.1793093718598; Tue, 27 Oct 2026 02:35:18 -0700 (PDT) X-Received: by 2002:a05:600c:c107:b0:4a5:e6fd:65e5 with SMTP id 5b1f17b1804b1-4a5e70ca839mr85162045e9.31.1793093717941; Tue, 27 Oct 2026 02:35:17 -0700 (PDT) Received: from redhat.com ([2a0d:6fc0:1536:fc00:b838:383:1c7:6e81]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e3ebc3932sm23007023f8f.18.2026.10.27.02.35.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Oct 2026 02:35:16 -0700 (PDT) Date: Tue, 27 Oct 2026 05:35:11 -0400 From: "Michael S. Tsirkin" To: Kevin Loughlin Cc: David Hildenbrand , Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Xuan Zhuo , Ard Biesheuvel , Kiryl Shutsemau , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Tom Lendacky , Ashish Kalra , Michael Roth , Rick Edgecombe , Andrew Morton , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Alexander Duyck , virtualization@lists.linux.dev, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sidharth Telang , Punit Salian , Peter Gonda , Ackerley Tng , Jacky Li , Steve Rutherford , David Skidmore Subject: Re: [PATCH 10/13] virtio_balloon: add higher-order page inflation Message-ID: <20261027052057-mutt-send-email-mst@kernel.org> References: <20261027025616.1632690-1-kevinloughlin@google.com> <20261027025616.1632690-11-kevinloughlin@google.com> X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 In-Reply-To: <20261027025616.1632690-11-kevinloughlin@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: LBYgbHZ2pXh5F2Bk6Yjp0LouIny-i67HxPNBggCBgAo_1793093719 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Oct 27, 2026 at 02:56:13AM +0000, Kevin Loughlin wrote: > In confidential computing guests requiring page state transitions, > unaccepted memory tracking operates at the EFI unaccepted memory unit > granularity (typically 2MB / order 9 on x86). Inflating the balloon > with 4KB pages would prevent unaccepting the backing 2MB unit. > > Inflate balloon pages at unaccepted_memory_order() when > virtballoon_cc_needs_state_transition() is true, while retaining > order-0 allocations for non-CoCo guests and CoCo guests that do not > use unaccepted memory transitions. When a higher-order balloon page > spans more 4KB balloon PFNs than VIRTIO_BALLOON_ARRAY_PFNS_MAX (256), > transmit its PFNs to the host in VIRTIO_BALLOON_ARRAY_PFNS_MAX chunks. > > Signed-off-by: Kevin Loughlin I'm not too happy that this rides on the legacy PFN thing which is after all limited to 44 bit addresses. And given it is passing around 2MB chunks, then one 16 byte descriptor covering all of 2MB would actually be more efficient than 512 4-byte PFNs. > --- > drivers/virtio/virtio_balloon.c | 87 ++++++++++++++++++++++++++------- > include/linux/balloon.h | 1 + > mm/balloon.c | 67 +++++++++++++++++++------ > 3 files changed, 121 insertions(+), 34 deletions(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 11f74848fdc4..d162c162b496 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -182,6 +182,13 @@ static void balloon_ack(struct virtqueue *vq) > wake_up(&vb->acked); > } > > +static inline bool virtballoon_cc_needs_state_transition(void) > +{ > + return IS_ENABLED(CONFIG_UNACCEPTED_MEMORY) && > + cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) && > + has_unaccepted_memory(); > +} > + > static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) > { > struct scatterlist sg; Put all this, and preferred order, etc etc in kernel core somewhere, and expose some sensible APIs that devices can use. > @@ -243,24 +250,49 @@ static void set_page_pfns(struct virtio_balloon *vb, > page_to_balloon_pfn(page) + i); > } > > +static void queue_page_pfns(struct virtio_balloon *vb, struct virtqueue *vq, > + struct page *page, unsigned int order) > +{ > + unsigned int nr_pages = 1 << order; > + unsigned int i; > + > + for (i = 0; i < nr_pages; i++) { > + set_page_pfns(vb, vb->pfns + vb->num_pfns, page + i); > + vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; > + if (vb->num_pfns == ARRAY_SIZE(vb->pfns)) { > + tell_host(vb, vq); > + vb->num_pfns = 0; > + } > + } > +} > + > +static inline unsigned int virtballoon_preferred_order(void) > +{ > + if (virtballoon_cc_needs_state_transition()) > + return unaccepted_memory_order(); > + return 0; > +} > + > static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num) > { > - unsigned int num_allocated_pages; > + unsigned int order = virtballoon_preferred_order(); > + unsigned int page_pfns = (1 << order) * VIRTIO_BALLOON_PAGES_PER_PAGE; > + unsigned int num_allocated_pages = 0; > struct page *page, *next; > unsigned int num_pfns; > LIST_HEAD(pages); > > - /* We can only do one array worth at a time. */ > - num = min(num, ARRAY_SIZE(vb->pfns)); > + /* We can only do one array or preferred-order page worth at a time. */ > + num = min(num, max_t(size_t, ARRAY_SIZE(vb->pfns), page_pfns)); > > for (num_pfns = 0; num_pfns < num; > - num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { > - page = balloon_page_alloc(); > + num_pfns += page_pfns) { > + page = balloon_pages_alloc(order); > > if (!page) { > dev_info_ratelimited(&vb->vdev->dev, > "Out of puff! Can't get %u pages\n", > - VIRTIO_BALLOON_PAGES_PER_PAGE); > + page_pfns); > /* Sleep for at least 1/5 of a second before retry. */ > msleep(200); > break; > @@ -274,15 +306,17 @@ static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num) > vb->num_pfns = 0; > > list_for_each_entry_safe(page, next, &pages, lru) { > + unsigned int page_order = compound_order(page); > + unsigned int pfns = (1 << page_order) * VIRTIO_BALLOON_PAGES_PER_PAGE; > + > list_del(&page->lru); > balloon_page_enqueue(&vb->vb_dev_info, page); > > - set_page_pfns(vb, vb->pfns + vb->num_pfns, page); > - vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; > - vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; > + vb->num_pages += pfns; > + num_allocated_pages += pfns; > + queue_page_pfns(vb, vb->inflate_vq, page, page_order); > } > > - num_allocated_pages = vb->num_pfns; > /* Did we get any? */ > if (vb->num_pfns != 0) > tell_host(vb, vb->inflate_vq); > @@ -304,28 +338,42 @@ static void release_pages_balloon(struct virtio_balloon *vb, > > static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num) > { > - unsigned int num_freed_pages; > + unsigned int order = virtballoon_preferred_order(); > + unsigned int page_pfns = (1 << order) * VIRTIO_BALLOON_PAGES_PER_PAGE; > + unsigned int num_freed_pages = 0; > struct page *page; > struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; > LIST_HEAD(pages); > > - /* We can only do one array worth at a time. */ > - num = min(num, ARRAY_SIZE(vb->pfns)); > + /* We can only do one array or preferred-order page worth at a time. */ > + num = min(num, max_t(size_t, ARRAY_SIZE(vb->pfns), page_pfns)); > > mutex_lock(&vb->balloon_lock); > /* We can't release more pages than taken */ > num = min(num, (size_t)vb->num_pages); > - for (vb->num_pfns = 0; vb->num_pfns < num; > - vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { > + vb->num_pfns = 0; > + while (num_freed_pages < num) { > + unsigned int dequeued_order; > + unsigned int dequeued_pfns; > + > page = balloon_page_dequeue(vb_dev_info); > if (!page) > break; > - set_page_pfns(vb, vb->pfns + vb->num_pfns, page); > + dequeued_order = compound_order(page); > + dequeued_pfns = (1 << dequeued_order) * VIRTIO_BALLOON_PAGES_PER_PAGE; > + > + if (num_freed_pages + dequeued_pfns > num && > + num_freed_pages > 0) { > + balloon_page_enqueue(vb_dev_info, page); > + break; > + } > + > + queue_page_pfns(vb, vb->deflate_vq, page, dequeued_order); > list_add(&page->lru, &pages); > - vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; > + vb->num_pages -= dequeued_pfns; > + num_freed_pages += dequeued_pfns; > } > > - num_freed_pages = vb->num_pfns; > /* > * Note that if > * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); > @@ -474,7 +522,8 @@ static inline s64 towards_target(struct virtio_balloon *vb) > * Aligned up to guest page size to avoid inflating and deflating > * balloon endlessly. > */ > - target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE); > + target = ALIGN((s64)num_pages, > + VIRTIO_BALLOON_PAGES_PER_PAGE << virtballoon_preferred_order()); > return target - vb->num_pages; > } > > diff --git a/include/linux/balloon.h b/include/linux/balloon.h > index ca5b15150f42..bc46e36b997f 100644 > --- a/include/linux/balloon.h > +++ b/include/linux/balloon.h > @@ -58,6 +58,7 @@ struct balloon_dev_info { > bool adjust_managed_page_count; > }; > > +struct page *balloon_pages_alloc(unsigned int order); > struct page *balloon_page_alloc(void); > void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, > struct page *page); > diff --git a/mm/balloon.c b/mm/balloon.c > index 96a8f1e20bc6..e9941d08d8e9 100644 > --- a/mm/balloon.c > +++ b/mm/balloon.c > @@ -27,9 +27,12 @@ static DEFINE_SPINLOCK(balloon_pages_lock); > static void balloon_page_insert(struct balloon_dev_info *balloon, > struct page *page) > { > + unsigned int i, nr_pages = 1U << compound_order(page); > + > lockdep_assert_held(&balloon_pages_lock); > - __SetPageOffline(page); > - if (IS_ENABLED(CONFIG_BALLOON_MIGRATION)) { > + for (i = 0; i < nr_pages; i++) > + __SetPageOffline(page + i); > + if (IS_ENABLED(CONFIG_BALLOON_MIGRATION) && !PageCompound(page)) { > SetPageMovableOps(page); > set_page_private(page, (unsigned long)balloon); > } > @@ -45,20 +48,31 @@ static void balloon_page_insert(struct balloon_dev_info *balloon, > */ > static void balloon_page_finalize(struct page *page) > { > + unsigned int i, nr_pages = 1U << compound_order(page); > + > lockdep_assert_held(&balloon_pages_lock); > - if (IS_ENABLED(CONFIG_BALLOON_MIGRATION)) > + if (IS_ENABLED(CONFIG_BALLOON_MIGRATION) && !PageCompound(page)) > set_page_private(page, 0); > - /* PageOffline is sticky until the page is freed to the buddy. */ > + /* > + * PageOffline is sticky on the head page until freed to the buddy, > + * which resets the head page's page_type in __free_pages_prepare(). > + * Clear PageOffline on tail pages here as __free_pages_prepare() > + * expects tail pages to have a default page_type. > + */ > + for (i = 1; i < nr_pages; i++) > + __ClearPageOffline(page + i); > } > > static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, > struct page *page) > { > + unsigned int order = compound_order(page); > + > balloon_page_insert(b_dev_info, page); > if (b_dev_info->adjust_managed_page_count) > - adjust_managed_page_count(page, -1); > - __count_vm_event(BALLOON_INFLATE); > - inc_node_page_state(page, NR_BALLOON_PAGES); > + adjust_managed_page_count(page, -(1L << order)); > + __count_vm_events(BALLOON_INFLATE, 1UL << order); > + mod_node_page_state(page_pgdat(page), NR_BALLOON_PAGES, 1L << order); > } > > /** > @@ -117,15 +131,18 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, > > spin_lock_irqsave(&balloon_pages_lock, flags); > list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { > + unsigned int order = compound_order(page); > + > if (n_pages == n_req_pages) > break; > list_del(&page->lru); > if (b_dev_info->adjust_managed_page_count) > - adjust_managed_page_count(page, 1); > + adjust_managed_page_count(page, 1L << order); > balloon_page_finalize(page); > - __count_vm_event(BALLOON_DEFLATE); > + __count_vm_events(BALLOON_DEFLATE, 1UL << order); > list_add(&page->lru, pages); > - dec_node_page_state(page, NR_BALLOON_PAGES); > + mod_node_page_state(page_pgdat(page), NR_BALLOON_PAGES, > + -(1L << order)); > n_pages++; > } > spin_unlock_irqrestore(&balloon_pages_lock, flags); > @@ -135,8 +152,9 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, > EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); > > /** > - * balloon_page_alloc - allocates a new page for insertion into the balloon > - * page list. > + * balloon_pages_alloc - allocates a new page of given order for insertion > + * into the balloon page list. > + * @order: allocation order > * > * Driver must call this function to properly allocate a new balloon page. > * Driver must call balloon_page_enqueue before definitively removing the page > @@ -144,16 +162,35 @@ EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); > * > * Return: struct page for the allocated page or NULL on allocation failure. > */ > -struct page *balloon_page_alloc(void) > +struct page *balloon_pages_alloc(unsigned int order) > { > gfp_t gfp_flags = __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN; > > - if (IS_ENABLED(CONFIG_BALLOON_MIGRATION)) > + if (IS_ENABLED(CONFIG_BALLOON_MIGRATION) && !order) > gfp_flags |= GFP_HIGHUSER_MOVABLE; > else > gfp_flags |= GFP_HIGHUSER; > > - return alloc_page(gfp_flags); > + if (order > 0) > + gfp_flags |= __GFP_COMP; > + > + return alloc_pages(gfp_flags, order); > +} > +EXPORT_SYMBOL_GPL(balloon_pages_alloc); > + > +/** > + * balloon_page_alloc - allocates a new page for insertion into the balloon > + * page list. > + * > + * Driver must call this function to properly allocate a new balloon page. > + * Driver must call balloon_page_enqueue before definitively removing the page > + * from the guest system. > + * > + * Return: struct page for the allocated page or NULL on allocation failure. > + */ > +struct page *balloon_page_alloc(void) > +{ > + return balloon_pages_alloc(0); > } > EXPORT_SYMBOL_GPL(balloon_page_alloc); > > -- > 2.56.0.307.g5fe7bd680c-goog