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Date: Mon, 19 Feb 2018 09:50:24 +0000
From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
To: Alex Williamson <alex.williamson@...hat.com>
CC: "eric.auger@...hat.com" <eric.auger@...hat.com>,
"pmorel@...ux.vnet.ibm.com" <pmorel@...ux.vnet.ibm.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Linuxarm <linuxarm@...wei.com>,
John Garry <john.garry@...wei.com>,
"xuwei (O)" <xuwei5@...wei.com>
Subject: RE: [PATCH v3 1/6] vfio/type1: Introduce iova list and add iommu
aperture validity check
Hi Alex,
> -----Original Message-----
> From: Alex Williamson [mailto:alex.williamson@...hat.com]
> Sent: Friday, February 16, 2018 8:49 PM
> To: Shameerali Kolothum Thodi <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
> <linuxarm@...wei.com>; John Garry <john.garry@...wei.com>; xuwei (O)
> <xuwei5@...wei.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.
Ok. I will take care of all the above inconsistencies.
> > +{
> > + 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.
Thanks. I got the test wrong for this case.
> > + 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.
Ok. My original thought was caller will free up in case of error.
> > + }
> > +
> > + 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.
Ok.
Thanks,
Shameer
> > + 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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