Re: [PATCH v7 03/11] iommu/vt-d: Add custom allocator for IOASID

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi Jacob,

On 10/25/19 3:54 AM, 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@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/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..ced1d89ef977 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -1706,6 +1706,9 @@ 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);

Since scalable mode is disabled if pasid allocator failed to register,
add sm_support(iommu) check here will be better.

> +
>   #endif
>   }
>   
> @@ -4910,6 +4913,44 @@ static int __init probe_acpi_namespace_devices(void)
>   	return 0;
>   }
>   
> +#ifdef CONFIG_INTEL_IOMMU_SVM
> +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 > 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 unbond.
> +	 */
> +	if (ioasid_find(NULL, ioasid, NULL)) {
> +		pr_alert("Cannot free active IOASID %d\n", ioasid);
> +		return;
> +	}
> +	vcmd_free_pasid(iommu, ioasid);
> +}
> +#endif
> +
>   int __init intel_iommu_init(void)
>   {
>   	int ret = -ENODEV;
> @@ -5020,6 +5061,32 @@ 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 (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap)) {
> +			pr_info("Register custom PASID allocator\n");
> +			/*
> +			 * 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;

It's insufficient to disable scalable mode by only clearing
intel_iommu_sm. The DMA_RTADDR_SMT bit in root entry has already been
set. Probably, you need to

for each iommu
	clear DMA_RTADDR_SMT in root entry

Alternatively, since vSVA is the only customer of this custom PASID
allocator, is it possible to only disable SVA here?

> +			}
> +		}
> +#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 1d4b8dcdc5d8..c624733cb2e6 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>
> @@ -546,6 +547,7 @@ 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.*/
> 

Best regards,
baolu
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