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[79.181.91.42]) by smtp.gmail.com with ESMTPSA id t197sm20634053qke.2.2019.07.24.12.47.20 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 24 Jul 2019 12:47:25 -0700 (PDT) Date: Wed, 24 Jul 2019 15:47:18 -0400 From: "Michael S. Tsirkin" To: Nitesh Narayan Lal Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, yang.zhang.wz@gmail.com, riel@surriel.com, david@redhat.com, dodgen@google.com, konrad.wilk@oracle.com, dhildenb@redhat.com, aarcange@redhat.com, alexander.duyck@gmail.com, john.starks@microsoft.com, dave.hansen@intel.com, mhocko@suse.com Subject: Re: [RFC][Patch v11 2/2] virtio-balloon: page_hinting: reporting to the host Message-ID: <20190724153951-mutt-send-email-mst@kernel.org> References: <20190710195158.19640-1-nitesh@redhat.com> <20190710195158.19640-3-nitesh@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190710195158.19640-3-nitesh@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 10, 2019 at 03:51:58PM -0400, Nitesh Narayan Lal wrote: > Enables the kernel to negotiate VIRTIO_BALLOON_F_HINTING feature with the > host. If it is available and page_hinting_flag is set to true, page_hinting > is enabled and its callbacks are configured along with the max_pages count > which indicates the maximum number of pages that can be isolated and hinted > at a time. Currently, only free pages of order >= (MAX_ORDER - 2) are > reported. To prevent any false OOM max_pages count is set to 16. > > By default page_hinting feature is enabled and gets loaded as soon > as the virtio-balloon driver is loaded. However, it could be disabled > by writing the page_hinting_flag which is a virtio-balloon parameter. > > Signed-off-by: Nitesh Narayan Lal > --- > drivers/virtio/Kconfig | 1 + > drivers/virtio/virtio_balloon.c | 91 ++++++++++++++++++++++++++++- > include/uapi/linux/virtio_balloon.h | 11 ++++ > 3 files changed, 102 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > index 023fc3bc01c6..dcc0cb4269a5 100644 > --- a/drivers/virtio/Kconfig > +++ b/drivers/virtio/Kconfig > @@ -47,6 +47,7 @@ config VIRTIO_BALLOON > tristate "Virtio balloon driver" > depends on VIRTIO > select MEMORY_BALLOON > + select PAGE_HINTING > ---help--- > This driver supports increasing and decreasing the amount > of memory within a KVM guest. > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 44339fc87cc7..1fb0eb0b2c20 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -18,6 +18,7 @@ > #include > #include > #include > +#include > > /* > * Balloon device works in 4K page units. So each page is pointed to by > @@ -35,6 +36,12 @@ > /* The size of a free page block in bytes */ > #define VIRTIO_BALLOON_FREE_PAGE_SIZE \ > (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT)) > +/* Number of isolated pages to be reported to the host at a time. > + * TODO: > + * 1. Set it via host. > + * 2. Find an optimal value for this. > + */ > +#define PAGE_HINTING_MAX_PAGES 16 > > #ifdef CONFIG_BALLOON_COMPACTION > static struct vfsmount *balloon_mnt; > @@ -45,6 +52,7 @@ enum virtio_balloon_vq { > VIRTIO_BALLOON_VQ_DEFLATE, > VIRTIO_BALLOON_VQ_STATS, > VIRTIO_BALLOON_VQ_FREE_PAGE, > + VIRTIO_BALLOON_VQ_HINTING, > VIRTIO_BALLOON_VQ_MAX > }; > > @@ -54,7 +62,8 @@ enum virtio_balloon_config_read { > > struct virtio_balloon { > struct virtio_device *vdev; > - struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; > + struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq, > + *hinting_vq; > > /* Balloon's own wq for cpu-intensive work items */ > struct workqueue_struct *balloon_wq; > @@ -112,6 +121,9 @@ struct virtio_balloon { > > /* To register a shrinker to shrink memory upon memory pressure */ > struct shrinker shrinker; > + > + /* Array object pointing at the isolated pages ready for hinting */ > + struct isolated_memory isolated_pages[PAGE_HINTING_MAX_PAGES]; > }; > > static struct virtio_device_id id_table[] = { > @@ -119,6 +131,66 @@ static struct virtio_device_id id_table[] = { > { 0 }, > }; > > +static struct page_hinting_config page_hinting_conf; > +bool page_hinting_flag = true; > +struct virtio_balloon *hvb; > +module_param(page_hinting_flag, bool, 0444); > +MODULE_PARM_DESC(page_hinting_flag, "Enable page hinting"); > + > +static int page_hinting_report(void) > +{ > + struct virtqueue *vq = hvb->hinting_vq; > + struct scatterlist sg; > + int err = 0, unused; > + > + mutex_lock(&hvb->balloon_lock); > + sg_init_one(&sg, hvb->isolated_pages, sizeof(hvb->isolated_pages[0]) * > + PAGE_HINTING_MAX_PAGES); > + err = virtqueue_add_outbuf(vq, &sg, 1, hvb, GFP_KERNEL); In Alex's patch, I really like it that he's passing pages as sg entries. IMHO that's both cleaner and allows seamless support for arbitrary page sizes. In particular .... > + if (!err) > + virtqueue_kick(hvb->hinting_vq); > + wait_event(hvb->acked, virtqueue_get_buf(vq, &unused)); > + mutex_unlock(&hvb->balloon_lock); > + return err; > +} > + > +void hint_pages(struct list_head *pages) > +{ > + struct device *dev = &hvb->vdev->dev; > + struct page *page, *next; > + int idx = 0, order, err; > + unsigned long pfn; > + > + list_for_each_entry_safe(page, next, pages, lru) { > + pfn = page_to_pfn(page); > + order = page_private(page); > + hvb->isolated_pages[idx].phys_addr = pfn << PAGE_SHIFT; > + hvb->isolated_pages[idx].size = (1 << order) * PAGE_SIZE; > + idx++; ... passing native endian-ness values to host creates pain for cross-endian configurations. > + } > + err = page_hinting_report(); > + if (err < 0) > + dev_err(dev, "Failed to hint pages, err = %d\n", err); > +} > + > +static void page_hinting_init(struct virtio_balloon *vb) > +{ > + struct device *dev = &vb->vdev->dev; > + int err; > + > + page_hinting_conf.hint_pages = hint_pages; > + page_hinting_conf.max_pages = PAGE_HINTING_MAX_PAGES; > + err = page_hinting_enable(&page_hinting_conf); > + if (err < 0) { > + dev_err(dev, "Failed to enable page-hinting, err = %d\n", err); It would be nicer to disable the feature bit then, or fail probe completely. > + page_hinting_flag = false; > + page_hinting_conf.hint_pages = NULL; > + page_hinting_conf.max_pages = 0; > + return; > + } > + hvb = vb; > +} > + > static u32 page_to_balloon_pfn(struct page *page) > { > unsigned long pfn = page_to_pfn(page); > @@ -475,6 +547,7 @@ static int init_vqs(struct virtio_balloon *vb) > names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; > names[VIRTIO_BALLOON_VQ_STATS] = NULL; > names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; > + names[VIRTIO_BALLOON_VQ_HINTING] = NULL; > > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > names[VIRTIO_BALLOON_VQ_STATS] = "stats"; > @@ -486,11 +559,18 @@ static int init_vqs(struct virtio_balloon *vb) > callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; > } > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { > + names[VIRTIO_BALLOON_VQ_HINTING] = "hinting_vq"; > + callbacks[VIRTIO_BALLOON_VQ_HINTING] = balloon_ack; > + } > err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, > vqs, callbacks, names, NULL, NULL); > if (err) > return err; > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) > + vb->hinting_vq = vqs[VIRTIO_BALLOON_VQ_HINTING]; > + > vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; > vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > @@ -929,6 +1009,9 @@ static int virtballoon_probe(struct virtio_device *vdev) > if (err) > goto out_del_balloon_wq; > } > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING) && > + page_hinting_flag) > + page_hinting_init(vb); > virtio_device_ready(vdev); > > if (towards_target(vb)) > @@ -976,6 +1059,10 @@ static void virtballoon_remove(struct virtio_device *vdev) > destroy_workqueue(vb->balloon_wq); > } > > + if (!page_hinting_flag) { > + hvb = NULL; > + page_hinting_disable(); > + } > remove_common(vb); > #ifdef CONFIG_BALLOON_COMPACTION > if (vb->vb_dev_info.inode) > @@ -1030,8 +1117,10 @@ static unsigned int features[] = { > VIRTIO_BALLOON_F_MUST_TELL_HOST, > VIRTIO_BALLOON_F_STATS_VQ, > VIRTIO_BALLOON_F_DEFLATE_ON_OOM, > + VIRTIO_BALLOON_F_HINTING, > VIRTIO_BALLOON_F_FREE_PAGE_HINT, > VIRTIO_BALLOON_F_PAGE_POISON, > + VIRTIO_BALLOON_F_HINTING, > }; > > static struct virtio_driver virtio_balloon_driver = { > diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h > index a1966cd7b677..29eed0ec83d3 100644 > --- a/include/uapi/linux/virtio_balloon.h > +++ b/include/uapi/linux/virtio_balloon.h > @@ -36,6 +36,8 @@ > #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */ > #define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */ > #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */ > +/* TODO: Find a better name to avoid any confusion with FREE_PAGE_HINT */ > +#define VIRTIO_BALLOON_F_HINTING 5 /* Page hinting virtqueue */ > > /* Size of a PFN in the balloon interface. */ > #define VIRTIO_BALLOON_PFN_SHIFT 12 > @@ -108,4 +110,13 @@ struct virtio_balloon_stat { > __virtio64 val; > } __attribute__((packed)); > > +/* > + * struct isolated_memory- holds the pages which will be reported to the host. > + * @phys_add: physical address associated with a page. > + * @size: total size of memory to be reported. > + */ > +struct isolated_memory { > + __virtio64 phys_addr; > + __virtio64 size; > +}; > #endif /* _LINUX_VIRTIO_BALLOON_H */ > -- > 2.21.0