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SubjectRe: [PATCH v4 20/22] iommu/vt-d: Add bind guest PASID support
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Hi Jacob and Yi,

On 6/9/19 9:44 PM, Jacob Pan wrote:
> When supporting guest SVA with emulated IOMMU, the guest PASID
> table is shadowed in VMM. Updates to guest vIOMMU PASID table
> will result in PASID cache flush which will be passed down to
> the host as bind guest PASID calls.
>
> For the SL page tables, it will be harvested from device's
> default domain (request w/o PASID), or aux domain in case of
> mediated device.
>
> .-------------. .---------------------------.
> | vIOMMU | | Guest process CR3, FL only|
> | | '---------------------------'
> .----------------/
> | PASID Entry |--- PASID cache flush -
> '-------------' |
> | | V
> | | CR3 in GPA
> '-------------'
> Guest
> ------| Shadow |--------------------------|--------
> v v v
> Host
> .-------------. .----------------------.
> | pIOMMU | | Bind FL for GVA-GPA |
> | | '----------------------'
> .----------------/ |
> | PASID Entry | V (Nested xlate)
> '----------------\.------------------------------.
> | | |SL for GPA-HPA, default domain|
> | | '------------------------------'
> '-------------'
> Where:
> - FL = First level/stage one page tables
> - SL = Second level/stage two page tables
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> ---
> drivers/iommu/intel-iommu.c | 4 +
> drivers/iommu/intel-svm.c | 187 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/intel-iommu.h | 13 ++-
> include/linux/intel-svm.h | 17 ++++
> 4 files changed, 219 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 7cfa0eb..3b4d712 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5782,6 +5782,10 @@ const struct iommu_ops intel_iommu_ops = {
> .dev_enable_feat = intel_iommu_dev_enable_feat,
> .dev_disable_feat = intel_iommu_dev_disable_feat,
> .pgsize_bitmap = INTEL_IOMMU_PGSIZES,
> +#ifdef CONFIG_INTEL_IOMMU_SVM
> + .sva_bind_gpasid = intel_svm_bind_gpasid,
> + .sva_unbind_gpasid = intel_svm_unbind_gpasid,
> +#endif
> };
>
> static void quirk_iommu_g4x_gfx(struct pci_dev *dev)
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 66d98e1..f06a82f 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -229,6 +229,193 @@ static LIST_HEAD(global_svm_list);
> list_for_each_entry(sdev, &svm->devs, list) \
> if (dev == sdev->dev) \
>
> +int intel_svm_bind_gpasid(struct iommu_domain *domain,
> + struct device *dev,
> + struct gpasid_bind_data *data)
> +{
> + struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> + struct intel_svm_dev *sdev;
> + struct intel_svm *svm = NULL;
> + struct dmar_domain *ddomain;
> + int ret = 0;
> +
> + if (WARN_ON(!iommu) || !data)
> + return -EINVAL;
> +
> + if (data->version != IOMMU_GPASID_BIND_VERSION_1 ||
> + data->format != IOMMU_PASID_FORMAT_INTEL_VTD)
> + return -EINVAL;
> +
> + if (dev_is_pci(dev)) {
> + /* VT-d supports devices with full 20 bit PASIDs only */
> + if (pci_max_pasids(to_pci_dev(dev)) != PASID_MAX)
> + return -EINVAL;
> + }
> +
> + /*
> + * We only check host PASID range, we have no knowledge to check
> + * guest PASID range nor do we use the guest PASID.
> + */
> + if (data->hpasid <= 0 || data->hpasid >= PASID_MAX)
> + return -EINVAL;
> +
> + ddomain = to_dmar_domain(domain);
> + /* REVISIT:
> + * Sanity check adddress width and paging mode support
> + * width matching in two dimensions:
> + * 1. paging mode CPU <= IOMMU
> + * 2. address width Guest <= Host.
> + */
> + mutex_lock(&pasid_mutex);
> + svm = ioasid_find(NULL, data->hpasid, NULL);
> + if (IS_ERR(svm)) {
> + ret = PTR_ERR(svm);
> + goto out;
> + }
> + if (svm) {
> + /*
> + * If we found svm for the PASID, there must be at
> + * least one device bond, otherwise svm should be freed.
> + */
> + BUG_ON(list_empty(&svm->devs));
> +
> + for_each_svm_dev() {
> + /* In case of multiple sub-devices of the same pdev assigned, we should
> + * allow multiple bind calls with the same PASID and pdev.
> + */
> + sdev->users++;
> + goto out;
> + }
> + } else {
> + /* We come here when PASID has never been bond to a device. */
> + svm = kzalloc(sizeof(*svm), GFP_KERNEL);
> + if (!svm) {
> + ret = -ENOMEM;
> + goto out;
> + }
> + /* REVISIT: upper layer/VFIO can track host process that bind the PASID.
> + * ioasid_set = mm might be sufficient for vfio to check pasid VMM
> + * ownership.
> + */
> + svm->mm = get_task_mm(current);
> + svm->pasid = data->hpasid;
> + if (data->flags & IOMMU_SVA_GPASID_VAL) {
> + svm->gpasid = data->gpasid;
> + svm->flags &= SVM_FLAG_GUEST_PASID;

I am guessing that you want to set this flag bit, so it should be

svm->flags |= SVM_FLAG_GUEST_PASID;

> + }
> + refcount_set(&svm->refs, 0);
> + ioasid_set_data(data->hpasid, svm);
> + INIT_LIST_HEAD_RCU(&svm->devs);
> + INIT_LIST_HEAD(&svm->list);
> +
> + mmput(svm->mm);
> + }
> + sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
> + if (!sdev) {
> + ret = -ENOMEM;
> + goto out;

I think you need to clean up svm if its device list is empty here, as
you said above:

+ if (svm) {
+ /*
+ * If we found svm for the PASID, there must be at
+ * least one device bond, otherwise svm should be freed.
+ */
+ BUG_ON(list_empty(&svm->devs));
+

> + }
> + sdev->dev = dev;
> + sdev->users = 1;
> +
> + /* Set up device context entry for PASID if not enabled already */
> + ret = intel_iommu_enable_pasid(iommu, sdev->dev);
> + if (ret) {
> + dev_err(dev, "Failed to enable PASID capability\n");
> + kfree(sdev);
> + goto out;
> + }
> +
> + /*
> + * For guest bind, we need to set up PASID table entry as follows:
> + * - FLPM matches guest paging mode
> + * - turn on nested mode
> + * - SL guest address width matching
> + */
> + ret = intel_pasid_setup_nested(iommu,
> + dev,
> + (pgd_t *)data->gpgd,
> + data->hpasid,
> + data->flags,
> + ddomain,
> + data->addr_width);
> + if (ret) {
> + dev_err(dev, "Failed to set up PASID %llu in nested mode, Err %d\n",
> + data->hpasid, ret);
> + kfree(sdev);
> + goto out;
> + }
> + svm->flags |= SVM_FLAG_GUEST_MODE;
> +
> + init_rcu_head(&sdev->rcu);
> + refcount_inc(&svm->refs);
> + list_add_rcu(&sdev->list, &svm->devs);
> + out:
> + mutex_unlock(&pasid_mutex);
> + return ret;
> +}
> +
> +int intel_svm_unbind_gpasid(struct device *dev, int pasid)
> +{
> + struct intel_svm_dev *sdev;
> + struct intel_iommu *iommu;
> + struct intel_svm *svm;
> + int ret = -EINVAL;
> +
> + mutex_lock(&pasid_mutex);
> + iommu = intel_svm_device_to_iommu(dev);
> + if (!iommu)
> + goto out;
> +
> + svm = ioasid_find(NULL, pasid, NULL);
> + if (IS_ERR(svm)) {
> + ret = PTR_ERR(svm);
> + goto out;
> + }
> +
> + if (!svm)
> + goto out;
> +
> + for_each_svm_dev() {
> + ret = 0;
> + sdev->users--;
> + if (!sdev->users) {
> + list_del_rcu(&sdev->list);
> + intel_pasid_tear_down_entry(iommu, dev, svm->pasid);
> + /* TODO: Drain in flight PRQ for the PASID since it
> + * may get reused soon, we don't want to
> + * confuse with its previous live.
> + * intel_svm_drain_prq(dev, pasid);
> + */
> + kfree_rcu(sdev, rcu);
> +
> + if (list_empty(&svm->devs)) {
> + list_del(&svm->list);
> + kfree(svm);
> + /*
> + * We do not free PASID here until explicit call
> + * from VFIO to free. The PASID life cycle
> + * management is largely tied to VFIO management
> + * of assigned device life cycles. In case of
> + * guest exit without a explicit free PASID call,
> + * the responsibility lies in VFIO layer to free
> + * the PASIDs allocated for the guest.
> + * For security reasons, VFIO has to track the
> + * PASID ownership per guest anyway to ensure
> + * that PASID allocated by one guest cannot be
> + * used by another.
> + */
> + ioasid_set_data(pasid, NULL);
> + }
> + }
> + break;
> + }
> + out:
> + mutex_unlock(&pasid_mutex);
> +
> + return ret;
> +}
> +
> int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ops *ops)
> {
> struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index b75f17d..94d3a9a 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -677,7 +677,9 @@ int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct device *dev);
> int intel_svm_init(struct intel_iommu *iommu);
> extern int intel_svm_enable_prq(struct intel_iommu *iommu);
> extern int intel_svm_finish_prq(struct intel_iommu *iommu);
> -
> +extern int intel_svm_bind_gpasid(struct iommu_domain *domain,
> + struct device *dev, struct gpasid_bind_data *data);
> +extern int intel_svm_unbind_gpasid(struct device *dev, int pasid);
> struct svm_dev_ops;
>
> struct intel_svm_dev {
> @@ -693,12 +695,19 @@ struct intel_svm_dev {
>
> struct intel_svm {
> struct mmu_notifier notifier;
> - struct mm_struct *mm;
> + union {
> + struct mm_struct *mm;
> + u64 gcr3;

I didn't see gcr3 being used anywhere? Anything I missed?

> + };
> struct intel_iommu *iommu;
> int flags;
> int pasid;
> + int gpasid; /* Guest PASID in case of vSVA bind with non-identity host
> + * to guest PASID mapping.
> + */
> struct list_head devs;
> struct list_head list;
> + refcount_t refs; /* Number of devices sharing this PASID */
> };
>
> extern struct intel_iommu *intel_svm_device_to_iommu(struct device *dev);
> diff --git a/include/linux/intel-svm.h b/include/linux/intel-svm.h
> index e3f7631..577d5df 100644
> --- a/include/linux/intel-svm.h
> +++ b/include/linux/intel-svm.h
> @@ -52,6 +52,23 @@ struct svm_dev_ops {
> * do such IOTLB flushes automatically.
> */
> #define SVM_FLAG_SUPERVISOR_MODE (1<<1)
> +/*
> + * The SVM_FLAG_GUEST_MODE flag is used when a guest process bind to a device.
> + * In this case the mm_struct is in the guest kernel or userspace, its life
> + * cycle is managed by VMM and VFIO layer. For IOMMU driver, this API provides
> + * means to bind/unbind guest CR3 with PASIDs allocated for a device.
> + */
> +#define SVM_FLAG_GUEST_MODE (1<<2)
> +/*
> + * The SVM_FLAG_GUEST_PASID flag is used when a guest has its own PASID space,
> + * which requires guest and host PASID translation at both directions. We keep
> + * track of guest PASID in order to provide lookup service to device drivers.
> + * One such example is a physical function (PF) driver that supports mediated
> + * device (mdev) assignment. Guest programming of mdev configuration space can
> + * only be done with guest PASID, therefore PF driver needs to find the matching
> + * host PASID to program the real hardware.
> + */
> +#define SVM_FLAG_GUEST_PASID (1<<3)
>
> #ifdef CONFIG_INTEL_IOMMU_SVM
>
>

Best regards,
Baolu

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