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Message-ID: <4tana2m46sjc6rkcrk7upy64v3tn7vrzploersngatmxf7b5mr@h5c3xmsa5xdd>
Date: Wed, 20 Mar 2024 12:23:11 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Wang Rong <w_angrong@....com>
Cc: mst@...hat.com, jasowang@...hat.com, kvm@...r.kernel.org,
virtualization@...ts.linux.dev, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] vhost/vdpa: Add MSI translation tables to iommu for
software-managed MSI
On Wed, Mar 20, 2024 at 06:19:12PM +0800, Wang Rong wrote:
>From: Rong Wang <w_angrong@....com>
>
>Once enable iommu domain for one device, the MSI
>translation tables have to be there for software-managed MSI.
>Otherwise, platform with software-managed MSI without an
>irq bypass function, can not get a correct memory write event
>from pcie, will not get irqs.
>The solution is to obtain the MSI phy base address from
>iommu reserved region, and set it to iommu MSI cookie,
>then translation tables will be created while request irq.
>
>Change log
>----------
>
>v1->v2:
>- add resv iotlb to avoid overlap mapping.
>v2->v3:
>- there is no need to export the iommu symbol anymore.
>
>Signed-off-by: Rong Wang <w_angrong@....com>
>---
> drivers/vhost/vdpa.c | 59 +++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 56 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>index ba52d128aeb7..28b56b10372b 100644
>--- a/drivers/vhost/vdpa.c
>+++ b/drivers/vhost/vdpa.c
>@@ -49,6 +49,7 @@ struct vhost_vdpa {
> struct completion completion;
> struct vdpa_device *vdpa;
> struct hlist_head as[VHOST_VDPA_IOTLB_BUCKETS];
>+ struct vhost_iotlb resv_iotlb;
> struct device dev;
> struct cdev cdev;
> atomic_t opened;
>@@ -247,6 +248,7 @@ static int _compat_vdpa_reset(struct vhost_vdpa *v)
> static int vhost_vdpa_reset(struct vhost_vdpa *v)
> {
> v->in_batch = 0;
>+ vhost_iotlb_reset(&v->resv_iotlb);
> return _compat_vdpa_reset(v);
> }
>
>@@ -1219,10 +1221,15 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> msg->iova + msg->size - 1 > v->range.last)
> return -EINVAL;
>
>+ if (vhost_iotlb_itree_first(&v->resv_iotlb, msg->iova,
>+ msg->iova + msg->size - 1))
>+ return -EINVAL;
>+
> if (vhost_iotlb_itree_first(iotlb, msg->iova,
> msg->iova + msg->size - 1))
> return -EEXIST;
>
>+
Unnecessary new line here.
> if (vdpa->use_va)
> return vhost_vdpa_va_map(v, iotlb, msg->iova, msg->size,
> msg->uaddr, msg->perm);
>@@ -1307,6 +1314,45 @@ static ssize_t vhost_vdpa_chr_write_iter(struct kiocb *iocb,
> return vhost_chr_write_iter(dev, from);
> }
>
>+static int vhost_vdpa_resv_iommu_region(struct iommu_domain *domain, struct device *dma_dev,
>+ struct vhost_iotlb *resv_iotlb)
>+{
>+ struct list_head dev_resv_regions;
>+ phys_addr_t resv_msi_base = 0;
>+ struct iommu_resv_region *region;
>+ int ret = 0;
>+ bool with_sw_msi = false;
>+ bool with_hw_msi = false;
>+
>+ INIT_LIST_HEAD(&dev_resv_regions);
>+ iommu_get_resv_regions(dma_dev, &dev_resv_regions);
>+
>+ list_for_each_entry(region, &dev_resv_regions, list) {
>+ ret = vhost_iotlb_add_range_ctx(resv_iotlb, region->start,
>+ region->start + region->length - 1,
>+ 0, 0, NULL);
>+ if (ret) {
>+ vhost_iotlb_reset(resv_iotlb);
>+ break;
>+ }
>+
>+ if (region->type == IOMMU_RESV_MSI)
>+ with_hw_msi = true;
>+
>+ if (region->type == IOMMU_RESV_SW_MSI) {
>+ resv_msi_base = region->start;
Can it happen that there are multiple regions of the IOMMU_RESV_SW_MSI
type?
In this case, is it correct to overwrite `resv_msi_base`?
>+ with_sw_msi = true;
>+ }
>+ }
>+
>+ if (!ret && !with_hw_msi && with_sw_msi)
>+ ret = iommu_get_msi_cookie(domain, resv_msi_base);
If `iommu_get_msi_cookie()` fails:
- Should we avoid calling iommu_put_resv_regions()?
- Should we also call `vhost_iotlb_reset(resv_iotlb)` like for the
vhost_iotlb_add_range_ctx() failure ?
If it is the case, maybe it's better to add an error label where do the
cleanup.
>+
>+ iommu_put_resv_regions(dma_dev, &dev_resv_regions);
>+
>+ return ret;
>+}
>+
> static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
> {
> struct vdpa_device *vdpa = v->vdpa;
>@@ -1335,11 +1381,16 @@ static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
>
> ret = iommu_attach_device(v->domain, dma_dev);
> if (ret)
>- goto err_attach;
>+ goto err_alloc_domain;
>
>- return 0;
>+ ret = vhost_vdpa_resv_iommu_region(v->domain, dma_dev, &v->resv_iotlb);
>+ if (ret)
>+ goto err_attach_device;
>
>-err_attach:
>+ return 0;
I suggest to add a new line here to separate the error path for the
success path.
>+err_attach_device:
>+ iommu_detach_device(v->domain, dma_dev);
>+err_alloc_domain:
> iommu_domain_free(v->domain);
> v->domain = NULL;
> return ret;
>@@ -1595,6 +1646,8 @@ static int vhost_vdpa_probe(struct vdpa_device *vdpa)
> goto err;
> }
>
>+ vhost_iotlb_init(&v->resv_iotlb, 0, 0);
>+
IIUC the lifetime of v->resv_iotlb, we initialize it here in the
vdpa_driver.probe() and we fill it during the `open` of the vhost-vdpa
character device.
So, should we reset it in the `release` of the vhost-vdpa character
device?
Thanks,
Stefano
> r = dev_set_name(&v->dev, "vhost-vdpa-%u", minor);
> if (r)
> goto err;
>--
>2.27.0
>
>
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