Re: [PATCH v6 02/10] iommu/vt-d: Add custom allocator for IOASID

[Raj, Ashok]

On Tue, Oct 22, 2019 at 04:53:15PM -0700, Jacob Pan wrote:
> 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@xxxxxxxxxxxxxxx>
> Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/Kconfig       |  1 +
>  drivers/iommu/intel-iommu.c | 67 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/intel-iommu.h |  2 ++
>  3 files changed, 70 insertions(+)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index fd50ddffffbf..961fe5795a90 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -211,6 +211,7 @@ config INTEL_IOMMU_SVM
>  	bool "Support for Shared Virtual Memory with Intel IOMMU"
>  	depends on INTEL_IOMMU && X86
>  	select PCI_PASID
> +	select IOASID
>  	select MMU_NOTIFIER
>  	help
>  	  Shared Virtual Memory (SVM) provides a facility for devices
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 3f974919d3bd..3aff0141c522 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -1706,6 +1706,8 @@ static void free_dmar_iommu(struct intel_iommu *iommu)
>  		if (ecap_prs(iommu->ecap))
>  			intel_svm_finish_prq(iommu);
>  	}
> +	ioasid_unregister_allocator(&iommu->pasid_allocator);
> +
>  #endif
>  }
>  
> @@ -4910,6 +4912,46 @@ static int __init probe_acpi_namespace_devices(void)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_INTEL_IOMMU_SVM

Maybe move them to intel-svm.c instead? that's where the bulk
of the svm support is?

> +static ioasid_t intel_ioasid_alloc(ioasid_t min, ioasid_t max, void *data)
> +{
> +	struct intel_iommu *iommu = data;
> +	ioasid_t 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 > PASID_MAX)
> +		return INVALID_IOASID;

What are these PASID_MIN/MAX? Do you check if these are within the 
limits supported by the iommu/vIOMMU as its enumerated?


> +
> +	if (vcmd_alloc_pasid(iommu, &ioasid))
> +		return INVALID_IOASID;
> +
> +	return ioasid;
> +}
> +
> +static void intel_ioasid_free(ioasid_t ioasid, void *data)
> +{
> +	struct iommu_pasid_alloc_info *svm;
> +	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 unbond.
> +	 */
> +	svm = ioasid_find(NULL, ioasid, NULL);
> +	if (!svm) {
> +		pr_warn("Freeing unbond IOASID %d\n", ioasid);
> +		return;
> +	}
> +	vcmd_free_pasid(iommu, ioasid);
> +}
> +#endif
> +
>  int __init intel_iommu_init(void)
>  {
>  	int ret = -ENODEV;
> @@ -5020,6 +5062,31 @@ int __init intel_iommu_init(void)
>  				       "%s", iommu->name);
>  		iommu_device_set_ops(&iommu->iommu, &intel_iommu_ops);
>  		iommu_device_register(&iommu->iommu);
> +#ifdef CONFIG_INTEL_IOMMU_SVM
> +		if (cap_caching_mode(iommu->cap) && sm_supported(iommu)) {

do you need to check against cap_caching_mode() or ecap_vcmd?


> +			/*
> +			 * Register a custom ASID allocator if we are running
> +			 * in a guest, the purpose is to have a system wide PASID
> +			 * namespace among all PASID users.
> +			 * There can be multiple vIOMMUs in each guest but only
> +			 * one allocator is active. All vIOMMU allocators will
> +			 * eventually be calling the same host allocator.
> +			 */
> +			iommu->pasid_allocator.alloc = intel_ioasid_alloc;
> +			iommu->pasid_allocator.free = intel_ioasid_free;
> +			iommu->pasid_allocator.pdata = (void *)iommu;
> +			ret = ioasid_register_allocator(&iommu->pasid_allocator);
> +			if (ret) {
> +				pr_warn("Custom PASID allocator registeration failed\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;
> +			}
> +		}
> +#endif
>  	}
>  
>  	bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index eea7468694a7..fb1973a761c1 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>
> @@ -542,6 +543,7 @@ 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
>