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Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D19D7F77B4@SHSMSX104.ccr.corp.intel.com>
Date: Sat, 28 Mar 2020 08:02:01 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Jacob Pan <jacob.jun.pan@...ux.intel.com>,
Lu Baolu <baolu.lu@...ux.intel.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Joerg Roedel <joro@...tes.org>,
David Woodhouse <dwmw2@...radead.org>,
"Alex Williamson" <alex.williamson@...hat.com>,
Jean-Philippe Brucker <jean-philippe@...aro.com>
CC: "Liu, Yi L" <yi.l.liu@...el.com>,
"Raj, Ashok" <ashok.raj@...el.com>,
Christoph Hellwig <hch@...radead.org>,
Jonathan Cameron <jic23@...nel.org>,
Eric Auger <eric.auger@...hat.com>,
Yi L <yi.l.liu@...ux.intel.com>
Subject: RE: [PATCH V10 06/11] iommu/vt-d: Add bind guest PASID support
> From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Sent: Saturday, March 21, 2020 7:28 AM
>
> 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@...ux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@...ux.intel.com>
> ---
> drivers/iommu/intel-iommu.c | 4 +
> drivers/iommu/intel-svm.c | 224
> ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/intel-iommu.h | 8 +-
> include/linux/intel-svm.h | 17 ++++
> 4 files changed, 252 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index e599b2537b1c..b1477cd423dd 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -6203,6 +6203,10 @@ const struct iommu_ops intel_iommu_ops = {
> .dev_disable_feat = intel_iommu_dev_disable_feat,
> .is_attach_deferred = intel_iommu_is_attach_deferred,
> .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_igfx(struct pci_dev *dev)
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index d7f2a5358900..47c0deb5ae56 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -226,6 +226,230 @@ static LIST_HEAD(global_svm_list);
> list_for_each_entry((sdev), &(svm)->devs, list) \
> if ((d) != (sdev)->dev) {} else
>
> +int intel_svm_bind_gpasid(struct iommu_domain *domain,
> + struct device *dev,
> + struct iommu_gpasid_bind_data *data)
> +{
> + struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> + struct dmar_domain *ddomain;
what about the full name e.g. dmar_domain? though a bit longer
but clearer than ddomain.
> + struct intel_svm_dev *sdev;
> + struct intel_svm *svm;
> + 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;
> + } else {
> + return -ENOTSUPP;
> + }
> +
> + /*
> + * 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);
> +
> + /* Sanity check paging mode support match between host and guest
> */
> + if (data->addr_width == ADDR_WIDTH_5LEVEL &&
> + !cap_5lp_support(iommu->cap)) {
> + pr_err("Cannot support 5 level paging requested by
> guest!\n");
> + return -EINVAL;
> + }
-ENOTSUPP?
> +
> + 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.
> + */
> + if (WARN_ON(list_empty(&svm->devs))) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + if (svm->mm == get_task_mm(current) &&
> + data->hpasid == svm->pasid &&
> + data->gpasid == svm->gpasid) {
> + pr_warn("Cannot bind the same guest-host PASID for
> the same process\n");
Sorry I didn’t get the rationale here. Isn't this branch is for binding the same
PASID to multiple devices? In that case definitely it is binding the same
guest-host PASID for the same process. otherwise if hpasid is different then
you'll hit a different intel_svm, while if gpasid is different how you can use
one intel_svm to hold multiple gpasids?
I feel the error condition should be the opposite. and suppose SVM_FLAG_
GUEST_PASID should be verified before checking gpasid.
> + mmput(svm->mm);
> + ret = -EINVAL;
> + goto out;
> + }
> + mmput(current->mm);
> +
> + for_each_svm_dev(sdev, 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.
Does sub-device mean mdev? I didn't find such notation in current iommu
directory.
and to make it clearer, "In case of multiple mdevs of the same pdev assigned
to the same guest process".
> + */
> + 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.
> + */
Above message is unclear about what should be revisited. Does it describe
the current implementation or the expected revision in the future?
> + 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;
> + }
> + ioasid_set_data(data->hpasid, svm);
> + INIT_LIST_HEAD_RCU(&svm->devs);
> + mmput(svm->mm);
> + }
> + sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
> + if (!sdev) {
> + if (list_empty(&svm->devs)) {
> + ioasid_set_data(data->hpasid, NULL);
> + kfree(svm);
> + }
> + ret = -ENOMEM;
> + goto out;
> + }
> + 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);
> + /*
> + * If this this a new PASID that never bond to a device, then
> + * the device list must be empty which indicates struct svm
> + * was allocated in this function.
> + */
the comment better move to the 1st occurrence when sdev allocation
fails. or even better put it in out label...
> + if (list_empty(&svm->devs)) {
> + ioasid_set_data(data->hpasid, NULL);
> + kfree(svm);
> + }
> + 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
> + */
looks above just explains the internal detail of intel_pasid_setup_nested,
which is not necessary to be here.
> + ret = intel_pasid_setup_nested(iommu,
> + dev,
> + (pgd_t *)data->gpgd,
> + data->hpasid,
> + &data->vtd,
> + ddomain,
> + data->addr_width);
It's worthy of an explanation here that setup_nested is required for
every device (even when they are sharing same intel_svm) because
we allocate pasid table per device. Otherwise I made a mistake to
think that only the 1st device bound to a new hpasid requires this
step. 😊
> + if (ret) {
> + dev_err(dev, "Failed to set up PASID %llu in nested mode,
> Err %d\n",
> + data->hpasid, ret);
> + /*
> + * PASID entry should be in cleared state if nested mode
> + * set up failed. So we only need to clear IOASID tracking
> + * data such that free call will succeed.
> + */
> + kfree(sdev);
> + if (list_empty(&svm->devs)) {
> + ioasid_set_data(data->hpasid, NULL);
> + kfree(svm);
> + }
> + goto out;
> + }
> + svm->flags |= SVM_FLAG_GUEST_MODE;
> +
> + init_rcu_head(&sdev->rcu);
> + 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_iommu *iommu = intel_svm_device_to_iommu(dev);
> + struct intel_svm_dev *sdev;
> + struct intel_svm *svm;
> + int ret = -EINVAL;
> +
> + if (WARN_ON(!iommu))
> + return -EINVAL;
> +
> + mutex_lock(&pasid_mutex);
> + svm = ioasid_find(NULL, pasid, NULL);
> + if (!svm) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + if (IS_ERR(svm)) {
> + ret = PTR_ERR(svm);
> + goto out;
> + }
> +
> + for_each_svm_dev(sdev, 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 life.
> + * intel_svm_drain_prq(dev, pasid);
> + */
> + kfree_rcu(sdev, rcu);
> +
> + if (list_empty(&svm->devs)) {
> + /*
> + * 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.
As commented in other patches, VFIO is only one example user of this API...
> + */
> + ioasid_set_data(pasid, NULL);
> + kfree(svm);
> + }
> + }
> + break;
> + }
what about no dev match? an -EINVAL is also required then.
> +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 eda1d6687144..85b05120940e 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -681,7 +681,9 @@ struct dmar_domain *find_domain(struct device
> *dev);
> extern void intel_svm_check(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 iommu_gpasid_bind_data *data);
> +extern int intel_svm_unbind_gpasid(struct device *dev, int pasid);
> struct svm_dev_ops;
>
> struct intel_svm_dev {
> @@ -698,9 +700,13 @@ struct intel_svm_dev {
> struct intel_svm {
> struct mmu_notifier notifier;
> struct mm_struct *mm;
> +
> 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.
> + */
we don't need to highlight identity or non-identity thing, since either way
shares the same infrastructure here and it is not the knowledge that the
kernel driver should assume
> struct list_head devs;
> struct list_head list;
> };
> diff --git a/include/linux/intel-svm.h b/include/linux/intel-svm.h
> index d7c403d0dd27..c19690937540 100644
> --- a/include/linux/intel-svm.h
> +++ b/include/linux/intel-svm.h
> @@ -44,6 +44,23 @@ 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
>
> --
> 2.7.4
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