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Date: Fri, 16 Feb 2018 13:49:17 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Cc: <eric.auger@...hat.com>, <pmorel@...ux.vnet.ibm.com>,
<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linuxarm@...wei.com>, <john.garry@...wei.com>,
<xuwei5@...ilicon.com>
Subject: Re: [PATCH v3 1/6] vfio/type1: Introduce iova list and add iommu
aperture validity check
On Thu, 15 Feb 2018 09:44:59 +0000
Shameer Kolothum <shameerali.kolothum.thodi@...wei.com> wrote:
> This introduces an iova list that is valid for dma mappings. Make
> sure the new iommu aperture window doesn't conflict with the current
> one or with any existing dma mappings during attach.
>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 183 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 181 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index e30e29a..4726f55 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -60,6 +60,7 @@ MODULE_PARM_DESC(disable_hugepages,
>
> struct vfio_iommu {
> struct list_head domain_list;
> + struct list_head iova_list;
> struct vfio_domain *external_domain; /* domain for external user */
> struct mutex lock;
> struct rb_root dma_list;
> @@ -92,6 +93,12 @@ struct vfio_group {
> struct list_head next;
> };
>
> +struct vfio_iova {
> + struct list_head list;
> + dma_addr_t start;
> + dma_addr_t end;
> +};
> +
> /*
> * Guest RAM pinning working set or DMA target
> */
> @@ -1192,6 +1199,142 @@ static bool vfio_iommu_has_sw_msi(struct iommu_group *group, phys_addr_t *base)
> return ret;
> }
>
> +/*
> + * This is a helper function to insert an address range to iova list.
> + * The list starts with a single entry corresponding to the IOMMU
> + * domain geometry to which the device group is attached. The list
> + * aperture gets modified when a new domain is added to the container
> + * if the new aperture doesn't conflict with the current one or with
> + * any existing dma mappings. The list is also modified to exclude
> + * any reserved regions associated with the device group.
> + */
> +static int vfio_insert_iova(phys_addr_t start, phys_addr_t end,
> + struct list_head *head)
The args seem more natural to me and have better consistency with the
other functions re-ordered as (head, start, end).
Also, if the iova list is dma_addr_t, why are we using phys_addr_t for
args?
> +{
> + struct vfio_iova *region;
> +
> + region = kmalloc(sizeof(*region), GFP_KERNEL);
> + if (!region)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(®ion->list);
> + region->start = start;
> + region->end = end;
> +
> + list_add_tail(®ion->list, head);
> + return 0;
> +}
> +
> +/*
> + * Check the new iommu aperture conflicts with existing aper or
> + * with any existing dma mappings.
> + */
> +static bool vfio_iommu_aper_conflict(struct vfio_iommu *iommu,
> + phys_addr_t start,
> + phys_addr_t end)
Same here, why phys_addr_t when comparing to dma_addr_t?
> +{
> + struct vfio_iova *first, *last;
> + struct list_head *iova = &iommu->iova_list;
> +
> + if (list_empty(iova))
> + return false;
> +
> + /* Disjoint sets, return conflict */
> + first = list_first_entry(iova, struct vfio_iova, list);
> + last = list_last_entry(iova, struct vfio_iova, list);
> + if ((start > last->end) || (end < first->start))
> + return true;
> +
> + /* Check for any existing dma mappings outside the new start */
> + if (start > first->start) {
> + if (vfio_find_dma(iommu, first->start, start - first->start))
> + return true;
> + }
> +
> + /* Check for any existing dma mappings outside the new end */
> + if (end < last->end) {
> + if (vfio_find_dma(iommu, end + 1, last->end - end))
> + return true;
> + }
> +
> + return false;
> +}
> +
> +/*
> + * Resize iommu iova aperture window. This is called only if the new
> + * aperture has no conflict with existing aperture and dma mappings.
> + */
> +static int vfio_iommu_aper_resize(struct list_head *iova,
> + dma_addr_t start,
> + dma_addr_t end)
And here we're back to dma_addr_t, let's be consistent.
> +{
> + struct vfio_iova *node, *next;
> +
> + if (list_empty(iova))
> + return vfio_insert_iova(start, end, iova);
> +
> + /* Adjust iova list start */
> + list_for_each_entry_safe(node, next, iova, list) {
> + if (start < node->start)
> + break;
> + if ((start >= node->start) && (start < node->end)) {
> + node->start = start;
> + break;
> + }
> + /* Delete nodes before new start */
> + list_del(&node->list);
> + kfree(node);
> + }
> +
> + /* Adjust iova list end */
> + list_for_each_entry_safe(node, next, iova, list) {
> + if (end > node->end)
> + continue;
> +
nit, extra blank line vs block above.
> + if ((end >= node->start) && (end < node->end)) {
This test is still incorrect, if end == node->start, we get a zero
sized range, we should have let it pass over to get deleted. Therefore
the first test should be (end > node->start). The second test was
changed and is now incorrect, if end == node->end, then we want to keep
this range, not delete it. This test should have remained (end <=
node->end) as it was in the previous version. IOW, my previous comment
was applied to the wrong test.
> + node->end = end;
> + continue;
> + }
> + /* Delete nodes after new end */
> + list_del(&node->list);
> + kfree(node);
> + }
> +
> + return 0;
> +}
> +
> +static int vfio_iommu_get_iova_copy(struct vfio_iommu *iommu,
> + struct list_head *iova_copy)
> +{
> +
> + struct list_head *iova = &iommu->iova_list;
> + struct vfio_iova *n;
> +
> + list_for_each_entry(n, iova, list) {
> + int ret;
> +
> + ret = vfio_insert_iova(n->start, n->end, iova_copy);
> + if (ret)
> + return ret;
Let's delete and free any entries added to the copy here too.
> + }
> +
> + return 0;
> +}
> +
> +static void vfio_iommu_insert_iova_copy(struct vfio_iommu *iommu,
> + struct list_head *iova_copy)
> +{
> + struct list_head *iova = &iommu->iova_list;
> + struct vfio_iova *n, *next;
> +
> + list_for_each_entry_safe(n, next, iova, list) {
> + list_del(&n->list);
> + kfree(n);
> + }
> +
> + list_splice_tail(iova_copy, iova);
> +}
> +
> static int vfio_iommu_type1_attach_group(void *iommu_data,
> struct iommu_group *iommu_group)
> {
> @@ -1202,6 +1345,9 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> int ret;
> bool resv_msi, msi_remap;
> phys_addr_t resv_msi_base;
> + struct iommu_domain_geometry geo;
> + struct list_head iova_copy;
> + struct vfio_iova *iova, *iova_next;
>
> mutex_lock(&iommu->lock);
>
> @@ -1271,6 +1417,26 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> if (ret)
> goto out_domain;
>
> + /* Get aperture info */
> + iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY, &geo);
> +
> + if (vfio_iommu_aper_conflict(iommu, geo.aperture_start,
> + geo.aperture_end)) {
> + ret = -EINVAL;
> + goto out_detach;
> + }
> +
> + /* Get a copy of the current iova list and work on it */
> + INIT_LIST_HEAD(&iova_copy);
We could have just declared this as:
LIST_HEAD(iova_copy);
to avoid needing to init it separately.
> + ret = vfio_iommu_get_iova_copy(iommu, &iova_copy);
> + if (ret)
> + goto out_detach;
> +
> + ret = vfio_iommu_aper_resize(&iova_copy, geo.aperture_start,
> + geo.aperture_end);
> + if (ret)
> + goto out_detach;
> +
> resv_msi = vfio_iommu_has_sw_msi(iommu_group, &resv_msi_base);
>
> INIT_LIST_HEAD(&domain->group_list);
> @@ -1304,8 +1470,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> list_add(&group->next, &d->group_list);
> iommu_domain_free(domain->domain);
> kfree(domain);
> - mutex_unlock(&iommu->lock);
> - return 0;
> + goto done;
> }
>
> ret = iommu_attach_group(domain->domain, iommu_group);
> @@ -1328,6 +1493,9 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> }
>
> list_add(&domain->next, &iommu->domain_list);
> +done:
> + /* Delete the old one and insert new iova list */
> + vfio_iommu_insert_iova_copy(iommu, &iova_copy);
>
> mutex_unlock(&iommu->lock);
>
> @@ -1337,6 +1505,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> iommu_detach_group(domain->domain, iommu_group);
> out_domain:
> iommu_domain_free(domain->domain);
> + list_for_each_entry_safe(iova, iova_next, &iova_copy, list)
> + kfree(iova);
Let's do the list_del() too, it's making me squirm that it's not here
and this is not a performance path.
> out_free:
> kfree(domain);
> kfree(group);
> @@ -1475,6 +1645,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
> }
>
> INIT_LIST_HEAD(&iommu->domain_list);
> + INIT_LIST_HEAD(&iommu->iova_list);
> iommu->dma_list = RB_ROOT;
> mutex_init(&iommu->lock);
> BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
> @@ -1502,6 +1673,7 @@ static void vfio_iommu_type1_release(void *iommu_data)
> {
> struct vfio_iommu *iommu = iommu_data;
> struct vfio_domain *domain, *domain_tmp;
> + struct vfio_iova *iova, *iova_next;
>
> if (iommu->external_domain) {
> vfio_release_domain(iommu->external_domain, true);
> @@ -1517,6 +1689,13 @@ static void vfio_iommu_type1_release(void *iommu_data)
> list_del(&domain->next);
> kfree(domain);
> }
> +
> + list_for_each_entry_safe(iova, iova_next,
> + &iommu->iova_list, list) {
> + list_del(&iova->list);
> + kfree(iova);
> + }
> +
> kfree(iommu);
> }
>
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