Message-Id: <B4126227-B436-4932-800E-27C2FFCA2301@arista.com>
Date:   Wed, 2 Jan 2019 14:22:10 +0000
From:   James Sewart <jamessewart@...sta.com>
To:     iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Dmitry Safonov <dima@...sta.com>
Subject: Re: [RFC v2] iommu/vt-d: Allow iommu_domain_alloc to allocate
 IOMMU_DOMAIN_DMA

Bump

> On 5 Dec 2018, at 17:19, James Sewart <jamessewart@...sta.com> wrote:
> 
> Hey,
> 
> There exists an issue in the logic used to determine domain association 
> with devices. Currently the driver uses find_or_alloc_domain to either 
> reuse an existing domain or allocate a new one if one isn’t found. Domains 
> should be shared between all members of an IOMMU group as this is the 
> minimum granularity that we can guarantee address space isolation.
> 
> The intel IOMMU driver exposes pci_device_group in intel_iommu_ops as the 
> function to call to determine the group of a device, this is implemented 
> in the generic IOMMU code and checks: dma aliases, upstream pcie switch 
> ACS, pci aliases, and pci function aliases. The find_or_alloc_domain code 
> currently only uses dma aliases to determine if a domain is shared. This 
> causes a disconnect between IOMMU groups and domains. We have observed 
> devices under a pcie switch each having their own domain but assigned the 
> same group.
> 
> One solution would be to fix the logic in find_or_alloc_domain to add 
> checks for the other conditions that a device may share a domain. However, 
> this duplicates code which the generic IOMMU code implements. Instead this 
> issue can be fixed by allowing the allocation of default_domain on the 
> IOMMU group. This is not currently supported as the intel driver does not 
> allow allocation of domain type IOMMU_DOMAIN_DMA.
> 
> Allowing allocation of DMA domains has the effect that the default_domain 
> is non NULL and is attached to a device when initialising. This delegates 
> the handling of domains to the generic IOMMU code. Once this is 
> implemented it is possible to remove the lazy allocation of domains 
> entirely.
> 
> This patch implements DMA and identity domains to be allocated for 
> external management. As it isn’t known which device will be attached to a 
> domain, the dma domain is not initialised at alloc time. Instead it is 
> allocated when attached. As we may lose RMRR mappings when attaching a 
> device to a new domain, we also ensure these are mapped at attach time.
> 
> This will likely conflict with the work done for auxiliary domains by 
> Baolu but the code to accommodate won’t change much.
> 
> I had also started on a patch to remove find_or_alloc_domain and various 
> functions that call it but had issues with edge cases such as 
> iommu_prepare_isa that is doing domain operations at IOMMU init time.
> 
> Cheers,
> James.
> 
> 
> ---
> drivers/iommu/intel-iommu.c | 159 +++++++++++++++++++++++++-----------
> 1 file changed, 110 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 41a4b8808802..6437cb2e9b22 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -351,6 +351,14 @@ static int hw_pass_through = 1;
> /* si_domain contains mulitple devices */
> #define DOMAIN_FLAG_STATIC_IDENTITY	(1 << 1)
> 
> +/* Domain managed externally, don't cleanup if it isn't attached
> + * to any devices. */
> +#define DOMAIN_FLAG_NO_CLEANUP	(1 << 2)
> +
> +/* Set after domain initialisation. Used when allocating dma domains to
> + * defer domain initialisation until it is attached to a device */
> +#define DOMAIN_FLAG_INITIALISED	(1 << 4)
> +
> #define for_each_domain_iommu(idx, domain)			\
> 	for (idx = 0; idx < g_num_of_iommus; idx++)		\
> 		if (domain->iommu_refcnt[idx])
> @@ -624,6 +632,16 @@ static inline int domain_type_is_vm_or_si(struct dmar_domain *domain)
> 				DOMAIN_FLAG_STATIC_IDENTITY);
> }
> 
> +static inline int domain_managed_externally(struct dmar_domain *domain)
> +{
> +	return domain->flags & DOMAIN_FLAG_NO_CLEANUP;
> +}
> +
> +static inline int domain_is_initialised(struct dmar_domain *domain)
> +{
> +	return domain->flags & DOMAIN_FLAG_INITIALISED;
> +}
> +
> static inline int domain_pfn_supported(struct dmar_domain *domain,
> 				       unsigned long pfn)
> {
> @@ -1717,7 +1735,7 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
> 
> 		__dmar_remove_one_dev_info(info);
> 
> -		if (!domain_type_is_vm_or_si(domain)) {
> +		if (!domain_managed_externally(domain)) {
> 			/*
> 			 * The domain_exit() function  can't be called under
> 			 * device_domain_lock, as it takes this lock itself.
> @@ -1951,6 +1969,7 @@ static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu,
> 	domain->pgd = (struct dma_pte *)alloc_pgtable_page(domain->nid);
> 	if (!domain->pgd)
> 		return -ENOMEM;
> +	domain->flags |= DOMAIN_FLAG_INITIALISED;
> 	__iommu_flush_cache(iommu, domain->pgd, PAGE_SIZE);
> 	return 0;
> }
> @@ -3234,11 +3253,9 @@ static int copy_translation_tables(struct intel_iommu *iommu)
> static int __init init_dmars(void)
> {
> 	struct dmar_drhd_unit *drhd;
> -	struct dmar_rmrr_unit *rmrr;
> 	bool copied_tables = false;
> -	struct device *dev;
> 	struct intel_iommu *iommu;
> -	int i, ret;
> +	int ret;
> 
> 	/*
> 	 * for each drhd
> @@ -4529,7 +4522,7 @@ static int device_notifier(struct notifier_block *nb,
> 		return 0;
> 
> 	dmar_remove_one_dev_info(domain, dev);
> -	if (!domain_type_is_vm_or_si(domain) && list_empty(&domain->devices))
> +	if (!domain_managed_externally(domain) && list_empty(&domain->devices))
> 		domain_exit(domain);
> 
> 	return 0;
> @@ -4930,6 +4923,7 @@ static int md_domain_init(struct dmar_domain *domain, int guest_width)
> 	domain->pgd = (struct dma_pte *)alloc_pgtable_page(domain->nid);
> 	if (!domain->pgd)
> 		return -ENOMEM;
> +	domain->flags |= DOMAIN_FLAG_INITIALISED;
> 	domain_flush_cache(domain, domain->pgd, PAGE_SIZE);
> 	return 0;
> }
> @@ -4938,28 +4932,65 @@ static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
> {
> 	struct dmar_domain *dmar_domain;
> 	struct iommu_domain *domain;
> +	int flags = DOMAIN_FLAG_NO_CLEANUP;
> +	int nid;
> 
> -	if (type != IOMMU_DOMAIN_UNMANAGED)
> -		return NULL;
> -
> -	dmar_domain = alloc_domain(DOMAIN_FLAG_VIRTUAL_MACHINE);
> -	if (!dmar_domain) {
> -		pr_err("Can't allocate dmar_domain\n");
> -		return NULL;
> -	}
> -	if (md_domain_init(dmar_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
> -		pr_err("Domain initialization failed\n");
> -		domain_exit(dmar_domain);
> +	switch (type) {
> +	case IOMMU_DOMAIN_UNMANAGED:
> +		flags |= DOMAIN_FLAG_VIRTUAL_MACHINE | DOMAIN_FLAG_INITIALISED;
> +		dmar_domain = alloc_domain(flags);
> +		if (!dmar_domain) {
> +			pr_err("Can't allocate dmar_domain\n");
> +			return NULL;
> +		}
> +		if (md_domain_init(dmar_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
> +			pr_err("Domain initialization failed\n");
> +			domain_exit(dmar_domain);
> +			return NULL;
> +		}
> +		domain_update_iommu_cap(dmar_domain);
> +		domain->geometry.aperture_start = 0;
> +		domain->geometry.aperture_end   = __DOMAIN_MAX_ADDR(dmar_domain->gaw);
> +		domain->geometry.force_aperture = true;
> +		break;
> +	case IOMMU_DOMAIN_DMA:
> +		dmar_domain = alloc_domain(flags);
> +		if (!dmar_domain) {
> +			pr_err("Can't allocate dmar_domain\n");
> +			return NULL;
> +		}
> +		/* init domain in device attach when we know IOMMU capabilities */
> +		break;
> +	case IOMMU_DOMAIN_IDENTITY:
> +		flags |= DOMAIN_FLAG_STATIC_IDENTITY | DOMAIN_FLAG_INITIALISED;
> +		dmar_domain = alloc_domain(flags);
> +		if (!dmar_domain) {
> +			pr_err("Can't allocate dmar_domain\n");
> +			return NULL;
> +		}
> +		if (md_domain_init(dmar_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
> +			pr_err("Domain initialization failed\n");
> +			domain_exit(dmar_domain);
> +			return NULL;
> +		}
> +		domain_update_iommu_cap(dmar_domain);
> +		for_each_online_node(nid) {
> +			unsigned long start_pfn, end_pfn;
> +			int i, ret;
> +
> +			for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
> +				ret = iommu_domain_identity_map(dmar_domain,
> +						PFN_PHYS(start_pfn), PFN_PHYS(end_pfn));
> +				if (ret)
> +					return NULL;
> +			}
> +		}
> +		break;
> +	default:
> 		return NULL;
> 	}
> -	domain_update_iommu_cap(dmar_domain);
> -
> -	domain = &dmar_domain->domain;
> -	domain->geometry.aperture_start = 0;
> -	domain->geometry.aperture_end   = __DOMAIN_MAX_ADDR(dmar_domain->gaw);
> -	domain->geometry.force_aperture = true;
> 
> -	return domain;
> +	return &dmar_domain->domain;
> }
> 
> static void intel_iommu_domain_free(struct iommu_domain *domain)
> @@ -4974,6 +5005,9 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
> 	struct intel_iommu *iommu;
> 	int addr_width;
> 	u8 bus, devfn;
> +	struct dmar_rmrr_unit *rmrr;
> +	struct device *i_dev;
> +	int i, ret;
> 
> 	if (device_is_rmrr_locked(dev)) {
> 		dev_warn(dev, "Device is ineligible for IOMMU domain attach due to platform RMRR requirement.  Contact your platform vendor.\n");
> @@ -4990,8 +5024,8 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
> 			dmar_remove_one_dev_info(old_domain, dev);
> 			rcu_read_unlock();
> 
> -			if (!domain_type_is_vm_or_si(old_domain) &&
> -			     list_empty(&old_domain->devices))
> +			if (list_empty(&old_domain->devices) &&
> +			     !domain_managed_externally(old_domain))
> 				domain_exit(old_domain);
> 		}
> 	}
> @@ -5000,6 +5034,12 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
> 	if (!iommu)
> 		return -ENODEV;
> 
> +	/* Initialise domain with IOMMU capabilities if it isn't already initialised */
> +	if (!domain_is_initialised(dmar_domain)) {
> +		if (domain_init(dmar_domain, iommu, DEFAULT_DOMAIN_ADDRESS_WIDTH))
> +			return -ENOMEM;
> +	}
> +
> 	/* check if this iommu agaw is sufficient for max mapped address */
> 	addr_width = agaw_to_width(iommu->agaw);
> 	if (addr_width > cap_mgaw(iommu->cap))
> @@ -5028,6 +5068,27 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
> 		dmar_domain->agaw--;
> 	}
> 
> +	if (domain_type_is_vm_or_si(dmar_domain))
> +		goto out;
> +
> +	/* Ensure DMA domain has devices RMRR */
> +	rcu_read_lock();
> +	for_each_rmrr_units(rmrr) {
> +		for_each_active_dev_scope(rmrr->devices, rmrr->devices_cnt,
> +					  i, i_dev) {
> +			if (i_dev != dev)
> +				continue;
> +
> +			ret = domain_prepare_identity_map(dev, dmar_domain,
> +							  rmrr->base_address,
> +							  rmrr->end_address);
> +			if (ret)
> +				dev_err(dev, "Mapping reserved region failed\n");
> +		}
> +	}
> +	rcu_read_unlock();
> +
> +out:
> 	return domain_add_dev_info(dmar_domain, dev);
> }
> 
> -- 
> 2.17.1
> 

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