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    SubjectRe: [PATCH 5/7] iommu/dma: add support for non-strict mode
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    On 31/05/18 08:42, Zhen Lei wrote:
    > 1. Save the related domain pointer in struct iommu_dma_cookie, make iovad
    > capable call domain->ops->flush_iotlb_all to flush TLB.
    > 2. Define a new iommu capable: IOMMU_CAP_NON_STRICT, which used to indicate
    > that the iommu domain support non-strict mode.
    > 3. During the iommu domain initialization phase, call capable() to check
    > whether it support non-strcit mode. If so, call init_iova_flush_queue
    > to register iovad->flush_cb callback.
    > 4. All unmap(contains iova-free) APIs will finally invoke __iommu_dma_unmap
    > -->iommu_dma_free_iova. Use iovad->flush_cb to check whether its related
    > iommu support non-strict mode or not, and call IOMMU_DOMAIN_IS_STRICT to
    > make sure the IOMMU_DOMAIN_UNMANAGED domain always follow strict mode.

    Once again, this is a whole load of complexity for a property which
    could just be statically encoded at allocation, e.g. in the cookie type.

    > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
    > ---
    > drivers/iommu/dma-iommu.c | 29 ++++++++++++++++++++++++++---
    > include/linux/iommu.h | 3 +++
    > 2 files changed, 29 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
    > index 4e885f7..2e116d9 100644
    > --- a/drivers/iommu/dma-iommu.c
    > +++ b/drivers/iommu/dma-iommu.c
    > @@ -55,6 +55,7 @@ struct iommu_dma_cookie {
    > };
    > struct list_head msi_page_list;
    > spinlock_t msi_lock;
    > + struct iommu_domain *domain;
    > };
    >
    > static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
    > @@ -64,7 +65,8 @@ static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
    > return PAGE_SIZE;
    > }
    >
    > -static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
    > +static struct iommu_dma_cookie *cookie_alloc(struct iommu_domain *domain,
    > + enum iommu_dma_cookie_type type)
    > {
    > struct iommu_dma_cookie *cookie;
    >
    > @@ -73,6 +75,7 @@ static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
    > spin_lock_init(&cookie->msi_lock);
    > INIT_LIST_HEAD(&cookie->msi_page_list);
    > cookie->type = type;
    > + cookie->domain = domain;
    > }
    > return cookie;
    > }
    > @@ -94,7 +97,7 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
    > if (domain->iova_cookie)
    > return -EEXIST;
    >
    > - domain->iova_cookie = cookie_alloc(IOMMU_DMA_IOVA_COOKIE);
    > + domain->iova_cookie = cookie_alloc(domain, IOMMU_DMA_IOVA_COOKIE);
    > if (!domain->iova_cookie)
    > return -ENOMEM;
    >
    > @@ -124,7 +127,7 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
    > if (domain->iova_cookie)
    > return -EEXIST;
    >
    > - cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE);
    > + cookie = cookie_alloc(domain, IOMMU_DMA_MSI_COOKIE);
    > if (!cookie)
    > return -ENOMEM;
    >
    > @@ -261,6 +264,17 @@ static int iova_reserve_iommu_regions(struct device *dev,
    > return ret;
    > }
    >
    > +static void iova_flush_iotlb_all(struct iova_domain *iovad)

    iommu_dma_flush...

    > +{
    > + struct iommu_dma_cookie *cookie;
    > + struct iommu_domain *domain;
    > +
    > + cookie = container_of(iovad, struct iommu_dma_cookie, iovad);
    > + domain = cookie->domain;
    > +
    > + domain->ops->flush_iotlb_all(domain);
    > +}
    > +
    > /**
    > * iommu_dma_init_domain - Initialise a DMA mapping domain
    > * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
    > @@ -276,6 +290,7 @@ static int iova_reserve_iommu_regions(struct device *dev,
    > int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
    > u64 size, struct device *dev)
    > {
    > + const struct iommu_ops *ops = domain->ops;
    > struct iommu_dma_cookie *cookie = domain->iova_cookie;
    > struct iova_domain *iovad = &cookie->iovad;
    > unsigned long order, base_pfn, end_pfn;
    > @@ -313,6 +328,11 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
    >
    > init_iova_domain(iovad, 1UL << order, base_pfn);
    >
    > + if (ops->capable && ops->capable(IOMMU_CAP_NON_STRICT)) {
    > + BUG_ON(!ops->flush_iotlb_all);
    > + init_iova_flush_queue(iovad, iova_flush_iotlb_all, NULL);
    > + }
    > +
    > return iova_reserve_iommu_regions(dev, domain);
    > }
    > EXPORT_SYMBOL(iommu_dma_init_domain);
    > @@ -392,6 +412,9 @@ static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie,
    > /* The MSI case is only ever cleaning up its most recent allocation */
    > if (cookie->type == IOMMU_DMA_MSI_COOKIE)
    > cookie->msi_iova -= size;
    > + else if (!IOMMU_DOMAIN_IS_STRICT(cookie->domain) && iovad->flush_cb)
    > + queue_iova(iovad, iova_pfn(iovad, iova),
    > + size >> iova_shift(iovad), 0);
    > else
    > free_iova_fast(iovad, iova_pfn(iovad, iova),
    > size >> iova_shift(iovad));
    > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
    > index 39b3150..01ff569 100644
    > --- a/include/linux/iommu.h
    > +++ b/include/linux/iommu.h
    > @@ -87,6 +87,8 @@ struct iommu_domain_geometry {
    > __IOMMU_DOMAIN_DMA_API)
    >
    > #define IOMMU_STRICT 1
    > +#define IOMMU_DOMAIN_IS_STRICT(domain) \
    > + (domain->type == IOMMU_DOMAIN_UNMANAGED)
    >
    > struct iommu_domain {
    > unsigned type;
    > @@ -103,6 +105,7 @@ enum iommu_cap {
    > transactions */
    > IOMMU_CAP_INTR_REMAP, /* IOMMU supports interrupt isolation */
    > IOMMU_CAP_NOEXEC, /* IOMMU_NOEXEC flag */
    > + IOMMU_CAP_NON_STRICT, /* IOMMU supports non-strict mode */

    This isn't a property of the IOMMU, it depends purely on the driver
    implementation. I think it also doesn't matter anyway - if a caller asks
    for lazy unmapping on their domain but the IOMMU driver just does strict
    unmaps anyway because that's all it supports, there's no actual harm done.

    Robin.

    > };
    >
    > /*
    >

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