RE: [PATCH V10 11/11] iommu/vt-d: Add custom allocator for IOASID

Tian, Kevin
2020-03-28T10:22:47Z

> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Sent: Saturday, March 21, 2020 7:28 AM
>
> When VT-d driver runs in the guest, PASID allocation must be
> performed via virtual command interface. This patch registers a
> custom IOASID allocator which takes precedence over the default
> XArray based allocator. The resulting IOASID allocation will always
> come from the host. This ensures that PASID namespace is system-
> wide.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> drivers/iommu/intel-iommu.c | 84
> +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/intel-iommu.h | 2 ++
> 2 files changed, 86 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index a76afb0fd51a..c1c0b0fb93c3 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -1757,6 +1757,9 @@ static void free_dmar_iommu(struct intel_iommu
> *iommu)
> if (ecap_prs(iommu->ecap))
> intel_svm_finish_prq(iommu);
> }
> + if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap))
> + ioasid_unregister_allocator(&iommu->pasid_allocator);
> +
> #endif
> }
>
> @@ -3291,6 +3294,84 @@ static int copy_translation_tables(struct
> intel_iommu *iommu)
> return ret;
> }
>
> +#ifdef CONFIG_INTEL_IOMMU_SVM
> +static ioasid_t intel_ioasid_alloc(ioasid_t min, ioasid_t max, void *data)

the name is too generic... can we add vcmd in the name to clarify
its purpose, e.g. intel_vcmd_ioasid_alloc?

> +{
> + struct intel_iommu *iommu = data;
> + ioasid_t ioasid;
> +
> + if (!iommu)
> + return INVALID_IOASID;
> + /*
> + * VT-d virtual command interface always uses the full 20 bit
> + * PASID range. Host can partition guest PASID range based on
> + * policies but it is out of guest's control.
> + */
> + if (min < PASID_MIN || max > intel_pasid_max_id)
> + return INVALID_IOASID;
> +
> + if (vcmd_alloc_pasid(iommu, &ioasid))
> + return INVALID_IOASID;
> +
> + return ioasid;
> +}
> +
> +static void intel_ioasid_free(ioasid_t ioasid, void *data)
> +{
> + struct intel_iommu *iommu = data;
> +
> + if (!iommu)
> + return;
> + /*
> + * Sanity check the ioasid owner is done at upper layer, e.g. VFIO
> + * We can only free the PASID when all the devices are unbound.
> + */
> + if (ioasid_find(NULL, ioasid, NULL)) {
> + pr_alert("Cannot free active IOASID %d\n", ioasid);
> + return;
> + }

However the sanity check is not done in default_free. Is there a reason
why using vcmd adds such new requirement?

> + vcmd_free_pasid(iommu, ioasid);
> +}
> +
> +static void register_pasid_allocator(struct intel_iommu *iommu)
> +{
> + /*
> + * If we are running in the host, no need for custom allocator
> + * in that PASIDs are allocated from the host system-wide.
> + */
> + if (!cap_caching_mode(iommu->cap))
> + return;

is it more accurate to check against vcmd capability?

> +
> + if (!sm_supported(iommu)) {
> + pr_warn("VT-d Scalable Mode not enabled, no PASID
> allocation\n");
> + return;
> + }
> +
> + /*
> + * Register a custom PASID allocator if we are running in a guest,
> + * guest PASID must be obtained via virtual command interface.
> + * There can be multiple vIOMMUs in each guest but only one
> allocator
> + * is active. All vIOMMU allocators will eventually be calling the same

which one? the first or last?

> + * host allocator.
> + */
> + if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap)) {
> + pr_info("Register custom PASID allocator\n");
> + iommu->pasid_allocator.alloc = intel_ioasid_alloc;
> + iommu->pasid_allocator.free = intel_ioasid_free;
> + iommu->pasid_allocator.pdata = (void *)iommu;
> + if (ioasid_register_allocator(&iommu->pasid_allocator)) {
> + pr_warn("Custom PASID allocator failed, scalable
> mode disabled\n");
> + /*
> + * Disable scalable mode on this IOMMU if there
> + * is no custom allocator. Mixing SM capable
> vIOMMU
> + * and non-SM vIOMMU are not supported.
> + */
> + intel_iommu_sm = 0;

since you register an allocator for every vIOMMU, means previously
registered allocators should also be unregistered here?

> + }
> + }
> +}
> +#endif
> +
> static int __init init_dmars(void)
> {
> struct dmar_drhd_unit *drhd;
> @@ -3408,6 +3489,9 @@ static int __init init_dmars(void)
> */
> for_each_active_iommu(iommu, drhd) {
> iommu_flush_write_buffer(iommu);
> +#ifdef CONFIG_INTEL_IOMMU_SVM
> + register_pasid_allocator(iommu);
> +#endif
> iommu_set_root_entry(iommu);
> iommu->flush.flush_context(iommu, 0, 0, 0,
> DMA_CCMD_GLOBAL_INVL);
> iommu->flush.flush_iotlb(iommu, 0, 0, 0,
> DMA_TLB_GLOBAL_FLUSH);
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 9cbf5357138b..9c357a325c72 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -19,6 +19,7 @@
> #include <linux/iommu.h>
> #include <linux/io-64-nonatomic-lo-hi.h>
> #include <linux/dmar.h>
> +#include <linux/ioasid.h>
>
> #include <asm/cacheflush.h>
> #include <asm/iommu.h>
> @@ -563,6 +564,7 @@ struct intel_iommu {
> #ifdef CONFIG_INTEL_IOMMU_SVM
> struct page_req_dsc *prq;
> unsigned char prq_name[16]; /* Name for PRQ interrupt */
> + struct ioasid_allocator_ops pasid_allocator; /* Custom allocator for
> PASIDs */
> #endif
> struct q_inval *qi; /* Queued invalidation info */
> u32 *iommu_state; /* Store iommu states between suspend and
> resume.*/
> --
> 2.7.4