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SubjectRe: [PATCH 3/4] iommu/vt-d: Allow IOMMU_DOMAIN_DMA and IOMMU_DOMAIN_IDENTITY to be allocated
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Hi,

On 3/4/19 11:46 PM, James Sewart wrote:
> Allowing IOMMU_DOMAIN_DMA type IOMMU domain to be allocated allows the
> default_domain of an iommu_group to be set. This delegates device-domain
> relationships to the generic IOMMU code.
>
> Signed-off-by: James Sewart <jamessewart@arista.com>
> ---
> drivers/iommu/intel-iommu.c | 113 +++++++++++++++++++++++++++---------
> 1 file changed, 84 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 8e0a4e2ff77f..71cd6bbfec05 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -309,6 +309,14 @@ 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_MANAGED_EXTERNALLY (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)

Why do you skip bit 3?

> +
> #define for_each_domain_iommu(idx, domain) \
> for (idx = 0; idx < g_num_of_iommus; idx++) \
> if (domain->iommu_refcnt[idx])
> @@ -558,6 +566,16 @@ 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_MANAGED_EXTERNALLY;
> +}
> +
> +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)
> {
> @@ -1662,7 +1680,7 @@ 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.
> @@ -1895,6 +1913,7 @@ 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;
> }
> @@ -2807,14 +2826,10 @@ static inline void iommu_prepare_isa(void)
>
> static int md_domain_init(struct dmar_domain *domain, int guest_width);
>
> -static int __init si_domain_init(int hw)
> +static int __init si_domain_init(struct dmar_domain *si_domain, int hw)
> {
> int nid, ret = 0;
>
> - si_domain = alloc_domain(DOMAIN_FLAG_STATIC_IDENTITY);
> - if (!si_domain)
> - return -EFAULT;
> -
> if (md_domain_init(si_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
> domain_exit(si_domain);
> return -EFAULT;
> @@ -3417,9 +3432,16 @@ static int __init init_dmars(void)
> check_tylersburg_isoch();
>
> if (iommu_identity_mapping) {
> - ret = si_domain_init(hw_pass_through);
> - if (ret)
> + si_domain = alloc_domain(DOMAIN_FLAG_STATIC_IDENTITY);

Where will this si_domain be used? We still need to keep the global
si_domain?

> + if (!si_domain) {
> + ret = -EFAULT;
> goto free_iommu;
> + }
> + ret = si_domain_init(si_domain, hw_pass_through);
> + if (ret) {
> + domain_exit(si_domain);
> + goto free_iommu;
> + }
> }
>
>
> @@ -4575,7 +4597,7 @@ 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;
> @@ -5020,6 +5042,7 @@ 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;
> }
> @@ -5028,28 +5051,54 @@ static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
> {
> struct dmar_domain *dmar_domain;
> struct iommu_domain *domain;
> + int flags = DOMAIN_FLAG_MANAGED_EXTERNALLY;
>
> - 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 = &dmar_domain->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");

Not necessary for memory allocation failure.

> + return NULL;
> + }
> + // init domain in device attach when we know IOMMU capabilities

Use /* */ for comments, please.

> + 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 (si_domain_init(dmar_domain, 0)) {
> + pr_err("Domain initialization failed\n");
> + domain_exit(dmar_domain);
> + return NULL;
> + }
> + break;

How about moving si domain allocation into a separated patch? There are
two significant changes here, so it worth a new patch for discussion.

1) a shared single si domain vs. per group si domain;
2) previously vt-d drivers determines what kind of devices should use
identity domain; Now, it turns to iommu generic layer, behavior will
be changed.

> + 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;
> + dmar_domain->domain.type = type;

Is it necessary to set this?

> + return &dmar_domain->domain;
> }
>
> static void intel_iommu_domain_free(struct iommu_domain *domain)
> @@ -5080,8 +5129,8 @@ 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);
> }
> }
> @@ -5090,6 +5139,12 @@ 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

Ditto.

> + if (!domain_is_initialised(dmar_domain)) {
> + if (domain_init(dmar_domain, iommu, DEFAULT_DOMAIN_ADDRESS_WIDTH))
> + return -ENOMEM;
> + }

Each domain, not matter the DMA domain or UNMANAGED domain, is allocated
first and then gets initialized during device attaching, right? If so,
why do we need to have a special DOMAIN_FLAG_INITIALISED flag for DMA
domains?

> +
> /* 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))
>

Best regards,
Lu Baolu
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