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Message-ID: <20161115151950.1e8ab7d6@t450s.home>
Date: Tue, 15 Nov 2016 15:19:50 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: Kirti Wankhede <kwankhede@...dia.com>
Cc: <pbonzini@...hat.com>, <kraxel@...hat.com>, <cjia@...dia.com>,
<qemu-devel@...gnu.org>, <kvm@...r.kernel.org>,
<kevin.tian@...el.com>, <jike.song@...el.com>,
<bjsdjshi@...ux.vnet.ibm.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v13 11/22] vfio iommu: Add blocking notifier to notify
DMA_UNMAP
On Tue, 15 Nov 2016 20:59:54 +0530
Kirti Wankhede <kwankhede@...dia.com> wrote:
> Added blocking notifier to IOMMU TYPE1 driver to notify vendor drivers
> about DMA_UNMAP.
> Exported two APIs vfio_register_notifier() and vfio_unregister_notifier().
> Notifier should be registered, if external user wants to use
> vfio_pin_pages()/vfio_unpin_pages() APIs to pin/unpin pages.
> Vendor driver should use VFIO_IOMMU_NOTIFY_DMA_UNMAP action to invalidate
> mappings.
>
> Signed-off-by: Kirti Wankhede <kwankhede@...dia.com>
> Signed-off-by: Neo Jia <cjia@...dia.com>
> Change-Id: I5910d0024d6be87f3e8d3e0ca0eaeaaa0b17f271
> ---
> drivers/vfio/vfio.c | 73 +++++++++++++++++++++++++++++++++++++++++
> drivers/vfio/vfio_iommu_type1.c | 63 +++++++++++++++++++++++++++++------
> include/linux/vfio.h | 11 +++++++
> 3 files changed, 137 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 3bf8a01bf67b..fa121d983991 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -1902,6 +1902,79 @@ err_unpin_pages:
> }
> EXPORT_SYMBOL(vfio_unpin_pages);
>
> +int vfio_register_notifier(struct device *dev, struct notifier_block *nb)
> +{
> + struct vfio_container *container;
> + struct vfio_group *group;
> + struct vfio_iommu_driver *driver;
> + ssize_t ret;
> +
> + if (!dev || !nb)
> + return -EINVAL;
> +
> + group = vfio_group_get_from_dev(dev);
> + if (IS_ERR(group))
> + return PTR_ERR(group);
> +
> + ret = vfio_group_add_container_user(group);
> + if (ret)
> + goto err_register_nb;
> +
> + container = group->container;
> + down_read(&container->group_lock);
> +
> + driver = container->iommu_driver;
> + if (likely(driver && driver->ops->register_notifier))
> + ret = driver->ops->register_notifier(container->iommu_data, nb);
> + else
> + ret = -ENOTTY;
> +
> + up_read(&container->group_lock);
> + vfio_group_try_dissolve_container(group);
> +
> +err_register_nb:
> + vfio_group_put(group);
> + return ret;
> +}
> +EXPORT_SYMBOL(vfio_register_notifier);
> +
> +int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
> +{
> + struct vfio_container *container;
> + struct vfio_group *group;
> + struct vfio_iommu_driver *driver;
> + ssize_t ret;
> +
> + if (!dev || !nb)
> + return -EINVAL;
> +
> + group = vfio_group_get_from_dev(dev);
> + if (IS_ERR(group))
> + return PTR_ERR(group);
> +
> + ret = vfio_group_add_container_user(group);
> + if (ret)
> + goto err_unregister_nb;
> +
> + container = group->container;
> + down_read(&container->group_lock);
> +
> + driver = container->iommu_driver;
> + if (likely(driver && driver->ops->unregister_notifier))
> + ret = driver->ops->unregister_notifier(container->iommu_data,
> + nb);
> + else
> + ret = -ENOTTY;
> +
> + up_read(&container->group_lock);
> + vfio_group_try_dissolve_container(group);
> +
> +err_unregister_nb:
> + vfio_group_put(group);
> + return ret;
> +}
> +EXPORT_SYMBOL(vfio_unregister_notifier);
> +
> /**
> * Module/class support
> */
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 0de7c20f66b1..c45a4822784e 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -38,6 +38,7 @@
> #include <linux/workqueue.h>
> #include <linux/pid_namespace.h>
> #include <linux/mdev.h>
> +#include <linux/notifier.h>
>
> #define DRIVER_VERSION "0.2"
> #define DRIVER_AUTHOR "Alex Williamson <alex.williamson@...hat.com>"
> @@ -60,6 +61,7 @@ struct vfio_iommu {
> struct vfio_domain *external_domain; /* domain for external user */
> struct mutex lock;
> struct rb_root dma_list;
> + struct blocking_notifier_head notifier;
> bool v2;
> bool nesting;
> };
> @@ -571,7 +573,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>
> mutex_lock(&iommu->lock);
>
> - if (!iommu->external_domain) {
> + /* Fail if notifier list is empty */
> + if ((!iommu->external_domain) || (!iommu->notifier.head)) {
> ret = -EINVAL;
> goto pin_done;
> }
> @@ -854,7 +857,28 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> */
> if (dma->task->mm != current->mm)
> break;
> +
> unmapped += dma->size;
> +
> + if (iommu->external_domain && !RB_EMPTY_ROOT(&dma->pfn_list)) {
> + struct vfio_iommu_type1_dma_unmap nb_unmap;
> +
> + nb_unmap.iova = dma->iova;
> + nb_unmap.size = dma->size;
> +
> + /*
> + * Notifier callback would call vfio_unpin_pages() which
> + * would acquire iommu->lock. Release lock here and
> + * reacquire it again.
> + */
> + mutex_unlock(&iommu->lock);
> + blocking_notifier_call_chain(&iommu->notifier,
> + VFIO_IOMMU_NOTIFY_DMA_UNMAP,
> + &nb_unmap);
> + mutex_lock(&iommu->lock);
> + if (WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list)))
> + break;
> + }
Why exactly do we need to notify per vfio_dma rather than per unmap
request? If we do the latter we can send the notify first, limiting us
to races where a page is pinned between the notify and the locking,
whereas here, even our dma pointer is suspect once we re-acquire the
lock, we don't technically know if another unmap could have removed
that already. Perhaps something like this (untested):
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index ee9a680..8504501 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -785,6 +785,8 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
struct vfio_dma *dma;
size_t unmapped = 0;
int ret = 0;
+ struct vfio_iommu_type1_dma_unmap nb_unmap = { .iova = unmap->iova,
+ .size = unmap->size };
mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
@@ -795,6 +797,14 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
WARN_ON(mask & PAGE_MASK);
+ /*
+ * Notify anyone (mdev vendor drivers) to invalidate and unmap
+ * iovas within the range we're about to unmap. Vendor drivers MUST
+ * unpin pages in response to an invalidation.
+ */
+ blocking_notifier_call_chain(&iommu->notifier,
+ VFIO_IOMMU_NOTIFY_DMA_UNMAP, &nb_unmap);
+
mutex_lock(&iommu->lock);
/*
@@ -853,25 +863,8 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
unmapped += dma->size;
- if (iommu->external_domain && !RB_EMPTY_ROOT(&dma->pfn_list)) {
- struct vfio_iommu_type1_dma_unmap nb_unmap;
+ WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list));
- nb_unmap.iova = dma->iova;
- nb_unmap.size = dma->size;
-
- /*
- * Notifier callback would call vfio_unpin_pages() which
- * would acquire iommu->lock. Release lock here and
- * reacquire it again.
- */
- mutex_unlock(&iommu->lock);
- blocking_notifier_call_chain(&iommu->notifier,
- VFIO_IOMMU_NOTIFY_DMA_UNMAP,
- &nb_unmap);
- mutex_lock(&iommu->lock);
- if (WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list)))
- break;
- }
vfio_remove_dma(iommu, dma);
}
> vfio_remove_dma(iommu, dma);
> }
>
> @@ -1439,6 +1463,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
> INIT_LIST_HEAD(&iommu->domain_list);
> iommu->dma_list = RB_ROOT;
> mutex_init(&iommu->lock);
> + BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
>
> return iommu;
> }
> @@ -1574,16 +1599,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
> return -ENOTTY;
> }
>
> +static int vfio_iommu_type1_register_notifier(void *iommu_data,
> + struct notifier_block *nb)
> +{
> + struct vfio_iommu *iommu = iommu_data;
> +
> + return blocking_notifier_chain_register(&iommu->notifier, nb);
> +}
> +
> +static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
> + struct notifier_block *nb)
> +{
> + struct vfio_iommu *iommu = iommu_data;
> +
> + return blocking_notifier_chain_unregister(&iommu->notifier, nb);
> +}
> +
> static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
> - .name = "vfio-iommu-type1",
> - .owner = THIS_MODULE,
> - .open = vfio_iommu_type1_open,
> - .release = vfio_iommu_type1_release,
> - .ioctl = vfio_iommu_type1_ioctl,
> - .attach_group = vfio_iommu_type1_attach_group,
> - .detach_group = vfio_iommu_type1_detach_group,
> - .pin_pages = vfio_iommu_type1_pin_pages,
> - .unpin_pages = vfio_iommu_type1_unpin_pages,
> + .name = "vfio-iommu-type1",
> + .owner = THIS_MODULE,
> + .open = vfio_iommu_type1_open,
> + .release = vfio_iommu_type1_release,
> + .ioctl = vfio_iommu_type1_ioctl,
> + .attach_group = vfio_iommu_type1_attach_group,
> + .detach_group = vfio_iommu_type1_detach_group,
> + .pin_pages = vfio_iommu_type1_pin_pages,
> + .unpin_pages = vfio_iommu_type1_unpin_pages,
> + .register_notifier = vfio_iommu_type1_register_notifier,
> + .unregister_notifier = vfio_iommu_type1_unregister_notifier,
> };
>
> static int __init vfio_iommu_type1_init(void)
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 420cdc928786..997442398c09 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -80,6 +80,10 @@ struct vfio_iommu_driver_ops {
> unsigned long *phys_pfn);
> int (*unpin_pages)(void *iommu_data,
> unsigned long *user_pfn, int npage);
> + int (*register_notifier)(void *iommu_data,
> + struct notifier_block *nb);
> + int (*unregister_notifier)(void *iommu_data,
> + struct notifier_block *nb);
> };
>
> extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
> @@ -139,6 +143,13 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
> extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
> int npage);
>
> +#define VFIO_IOMMU_NOTIFY_DMA_UNMAP 1
> +
> +extern int vfio_register_notifier(struct device *dev,
> + struct notifier_block *nb);
> +
> +extern int vfio_unregister_notifier(struct device *dev,
> + struct notifier_block *nb);
> /*
> * IRQfd - generic
> */
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