Re: [PATCH v5 04/23] iommu/vt-d: add bind_pasid_table function

Lu Baolu
2018-05-13T09:29:47Z

Hi,

On 05/12/2018 04:53 AM, Jacob Pan wrote:
> Add Intel VT-d ops to the generic iommu_bind_pasid_table API
> functions.
>
> The primary use case is for direct assignment of SVM capable
> device. Originated from emulated IOMMU in the guest, the request goes
> through many layers (e.g. VFIO). Upon calling host IOMMU driver, caller
> passes guest PASID table pointer (GPA) and size.
>
> Device context table entry is modified by Intel IOMMU specific
> bind_pasid_table function. This will turn on nesting mode and matching
> translation type.
>
> The unbind operation restores default context mapping.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> Signed-off-by: Ashok Raj <ashok.raj@intel.com>
> ---
> drivers/iommu/intel-iommu.c | 122 ++++++++++++++++++++++++++++++++++++++++++
> include/linux/dma_remapping.h | 1 +
> 2 files changed, 123 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index a0f81a4..4623294 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -2409,6 +2409,7 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
> info->ats_supported = info->pasid_supported = info->pri_supported = 0;
> info->ats_enabled = info->pasid_enabled = info->pri_enabled = 0;
> info->ats_qdep = 0;
> + info->pasid_table_bound = 0;
> info->dev = dev;
> info->domain = domain;
> info->iommu = iommu;
> @@ -5132,6 +5133,7 @@ static void intel_iommu_put_resv_regions(struct device *dev,
>
> #ifdef CONFIG_INTEL_IOMMU_SVM
> #define MAX_NR_PASID_BITS (20)
> +#define MIN_NR_PASID_BITS (5)
> static inline unsigned long intel_iommu_get_pts(struct intel_iommu *iommu)
> {
> /*
> @@ -5258,6 +5260,122 @@ struct intel_iommu *intel_svm_device_to_iommu(struct device *dev)
>
> return iommu;
> }
> +
> +static int intel_iommu_bind_pasid_table(struct iommu_domain *domain,
> + struct device *dev, struct pasid_table_config *pasidt_binfo)
> +{
> + struct intel_iommu *iommu;
> + struct context_entry *context;
> + struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> + struct device_domain_info *info;
> + struct pci_dev *pdev;
> + u8 bus, devfn, host_table_pasid_bits;
> + u16 did, sid;
> + int ret = 0;
> + unsigned long flags;
> + u64 ctx_lo;

I personally prefer to have this in order.

struct dmar_domain *dmar_domain = to_dmar_domain(domain);
u8 bus, devfn, host_table_pasid_bits;
struct device_domain_info *info;
struct context_entry *context;
struct intel_iommu *iommu;
struct pci_dev *pdev;
unsigned long flags;
u16 did, sid;
int ret = 0;
u64 ctx_lo;

> +
> + if ((pasidt_binfo->version != PASID_TABLE_CFG_VERSION_1) ||

Unnecessary parentheses.

> + pasidt_binfo->bytes != sizeof(*pasidt_binfo))

Alignment should match open parenthesis.

> + return -EINVAL;
> + iommu = device_to_iommu(dev, &bus, &devfn);
> + if (!iommu)
> + return -ENODEV;
> + /* VT-d spec section 9.4 says pasid table size is encoded as 2^(x+5) */
> + host_table_pasid_bits = intel_iommu_get_pts(iommu) + MIN_NR_PASID_BITS;
> + if (!pasidt_binfo || pasidt_binfo->pasid_bits > host_table_pasid_bits ||

"!pasidt_binfo" checking should be moved up to the version checking.

> + pasidt_binfo->pasid_bits < MIN_NR_PASID_BITS) {
> + pr_err("Invalid gPASID bits %d, host range %d - %d\n",

How about dev_err()?

> + pasidt_binfo->pasid_bits,
> + MIN_NR_PASID_BITS, host_table_pasid_bits);
> + return -ERANGE;
> + }
> + if (!ecap_nest(iommu->ecap)) {
> + dev_err(dev, "Cannot bind PASID table, no nested translation\n");
> + ret = -ENODEV;
> + goto out;

How about
+ return -ENODEV;
?

> + }
> + pdev = to_pci_dev(dev);

We can't always assume that it is a PCI device, right?

> + sid = PCI_DEVID(bus, devfn);
> + info = dev->archdata.iommu;
> +
> + if (!info) {
> + dev_err(dev, "Invalid device domain info\n");
> + ret = -EINVAL;
> + goto out;
> + }
> + if (info->pasid_table_bound) {

We should do this checking with lock hold.

Otherwise,

Thread A on CPUx Thread B on CPUy
=========== ============
check pasid_table_bound check pasid_table_bound

mutex_lock()
Setup context
pasid_table_bound = 1
mutex_unlock()

mutex_lock()
Setup context
pasid_table_bound = 1
mutex_unlock()

> + dev_err(dev, "Device PASID table already bound\n");
> + ret = -EBUSY;
> + goto out;
> + }
> + if (!info->pasid_enabled) {
> + ret = pci_enable_pasid(pdev, info->pasid_supported & ~1);
> + if (ret) {
> + dev_err(dev, "Failed to enable PASID\n");
> + goto out;
> + }
> + }

I prefer a blank line here.

> + spin_lock_irqsave(&iommu->lock, flags);
> + context = iommu_context_addr(iommu, bus, devfn, 0);
> + if (!context_present(context)) {
> + dev_err(dev, "Context not present\n");
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + /* Anticipate guest to use SVM and owns the first level, so we turn
> + * nested mode on
> + */
> + ctx_lo = context[0].lo;
> + ctx_lo |= CONTEXT_NESTE | CONTEXT_PRS | CONTEXT_PASIDE;
> + ctx_lo &= ~CONTEXT_TT_MASK;
> + ctx_lo |= CONTEXT_TT_DEV_IOTLB << 2;
> + context[0].lo = ctx_lo;
> +
> + /* Assign guest PASID table pointer and size order */
> + ctx_lo = (pasidt_binfo->base_ptr & VTD_PAGE_MASK) |
> + (pasidt_binfo->pasid_bits - MIN_NR_PASID_BITS);
> + context[1].lo = ctx_lo;
> + /* make sure context entry is updated before flushing */
> + wmb();
> + did = dmar_domain->iommu_did[iommu->seq_id];
> + iommu->flush.flush_context(iommu, did,
> + (((u16)bus) << 8) | devfn,
> + DMA_CCMD_MASK_NOBIT,
> + DMA_CCMD_DEVICE_INVL);
> + iommu->flush.flush_iotlb(iommu, did, 0, 0, DMA_TLB_DSI_FLUSH);
> + info->pasid_table_bound = 1;
> +out_unlock:
> + spin_unlock_irqrestore(&iommu->lock, flags);
> +out:
> + return ret;
> +}
> +
> +static void intel_iommu_unbind_pasid_table(struct iommu_domain *domain,
> + struct device *dev)
> +{
> + struct intel_iommu *iommu;
> + struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> + struct device_domain_info *info;
> + u8 bus, devfn;
> +
> + info = dev->archdata.iommu;
> + if (!info) {
> + dev_err(dev, "Invalid device domain info\n");
> + return;
> + }
> + iommu = device_to_iommu(dev, &bus, &devfn);
> + if (!iommu) {
> + dev_err(dev, "No IOMMU for device to unbind PASID table\n");
> + return;
> + }
> +
> + domain_context_clear(iommu, dev);
> +
> + domain_context_mapping_one(dmar_domain, iommu, bus, devfn);
> + info->pasid_table_bound = 0;
> +}
> #endif /* CONFIG_INTEL_IOMMU_SVM */
>
> const struct iommu_ops intel_iommu_ops = {
> @@ -5266,6 +5384,10 @@ const struct iommu_ops intel_iommu_ops = {
> .domain_free = intel_iommu_domain_free,
> .attach_dev = intel_iommu_attach_device,
> .detach_dev = intel_iommu_detach_device,
> +#ifdef CONFIG_INTEL_IOMMU_SVM
> + .bind_pasid_table = intel_iommu_bind_pasid_table,
> + .unbind_pasid_table = intel_iommu_unbind_pasid_table,
> +#endif
> .map = intel_iommu_map,
> .unmap = intel_iommu_unmap,
> .map_sg = default_iommu_map_sg,
> diff --git a/include/linux/dma_remapping.h b/include/linux/dma_remapping.h
> index 21b3e7d..db290b2 100644
> --- a/include/linux/dma_remapping.h
> +++ b/include/linux/dma_remapping.h
> @@ -28,6 +28,7 @@
>
> #define CONTEXT_DINVE (1ULL << 8)
> #define CONTEXT_PRS (1ULL << 9)
> +#define CONTEXT_NESTE (1ULL << 10)
> #define CONTEXT_PASIDE (1ULL << 11)
>
> struct intel_iommu;

Best regards,
Lu Baolu