[RFC 09/16] RDMA/core: Separate DMA mapping to caching IOVA and page linkage

Leon Romanovsky
2024-03-05T13:34:27Z

Reuse newly added DMA API to cache IOVA and only link/unlink pages
in fast path.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
drivers/infiniband/core/umem_odp.c | 57 ++----------------------------
drivers/infiniband/hw/mlx5/odp.c | 22 +++++++++++-
include/rdma/ib_umem_odp.h | 8 +----
include/rdma/ib_verbs.h | 36 +++++++++++++++++++
4 files changed, 61 insertions(+), 62 deletions(-)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index 3619fb78f786..1301009a6b78 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -81,20 +81,13 @@ static inline int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
if (!umem_odp->pfn_list)
return -ENOMEM;

- umem_odp->dma_list = kvcalloc(
- ndmas, sizeof(*umem_odp->dma_list), GFP_KERNEL);
- if (!umem_odp->dma_list) {
- ret = -ENOMEM;
- goto out_pfn_list;
- }

umem_odp->iova.dev = dev->dma_device;
umem_odp->iova.size = end - start;
umem_odp->iova.dir = DMA_BIDIRECTIONAL;
ret = ib_dma_alloc_iova(dev, &umem_odp->iova);
if (ret)
- goto out_dma_list;
-
+ goto out_pfn_list;

ret = mmu_interval_notifier_insert(&umem_odp->notifier,
umem_odp->umem.owning_mm,
@@ -107,8 +100,6 @@ static inline int ib_init_umem_odp(struct ib_umem_odp *umem_odp,

out_free_iova:
ib_dma_free_iova(dev, &umem_odp->iova);
-out_dma_list:
- kvfree(umem_odp->dma_list);
out_pfn_list:
kvfree(umem_odp->pfn_list);
return ret;
@@ -288,7 +279,6 @@ void ib_umem_odp_release(struct ib_umem_odp *umem_odp)
mutex_unlock(&umem_odp->umem_mutex);
mmu_interval_notifier_remove(&umem_odp->notifier);
ib_dma_free_iova(dev, &umem_odp->iova);
- kvfree(umem_odp->dma_list);
kvfree(umem_odp->pfn_list);
}
put_pid(umem_odp->tgid);
@@ -296,40 +286,10 @@ void ib_umem_odp_release(struct ib_umem_odp *umem_odp)
}
EXPORT_SYMBOL(ib_umem_odp_release);

-/*
- * Map for DMA and insert a single page into the on-demand paging page tables.
- *
- * @umem: the umem to insert the page to.
- * @dma_index: index in the umem to add the dma to.
- * @page: the page struct to map and add.
- * @access_mask: access permissions needed for this page.
- *
- * The function returns -EFAULT if the DMA mapping operation fails.
- *
- */
-static int ib_umem_odp_map_dma_single_page(
- struct ib_umem_odp *umem_odp,
- unsigned int dma_index,
- struct page *page)
-{
- struct ib_device *dev = umem_odp->umem.ibdev;
- dma_addr_t *dma_addr = &umem_odp->dma_list[dma_index];
-
- *dma_addr = ib_dma_map_page(dev, page, 0, 1 << umem_odp->page_shift,
- DMA_BIDIRECTIONAL);
- if (ib_dma_mapping_error(dev, *dma_addr)) {
- *dma_addr = 0;
- return -EFAULT;
- }
- umem_odp->npages++;
- return 0;
-}
-
/**
* ib_umem_odp_map_dma_and_lock - DMA map userspace memory in an ODP MR and lock it.
*
* Maps the range passed in the argument to DMA addresses.
- * The DMA addresses of the mapped pages is updated in umem_odp->dma_list.
* Upon success the ODP MR will be locked to let caller complete its device
* page table update.
*
@@ -437,15 +397,6 @@ int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,
__func__, hmm_order, page_shift);
break;
}
-
- ret = ib_umem_odp_map_dma_single_page(
- umem_odp, dma_index, hmm_pfn_to_page(range.hmm_pfns[pfn_index]));
- if (ret < 0) {
- ibdev_dbg(umem_odp->umem.ibdev,
- "ib_umem_odp_map_dma_single_page failed with error %d\n", ret);
- break;
- }
- range.hmm_pfns[pfn_index] |= HMM_PFN_STICKY;
}
/* upon success lock should stay on hold for the callee */
if (!ret)
@@ -465,7 +416,6 @@ EXPORT_SYMBOL(ib_umem_odp_map_dma_and_lock);
void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
u64 bound)
{
- dma_addr_t dma;
int idx;
u64 addr;
struct ib_device *dev = umem_odp->umem.ibdev;
@@ -479,15 +429,14 @@ void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
struct page *page = hmm_pfn_to_page(umem_odp->pfn_list[pfn_idx]);

idx = (addr - ib_umem_start(umem_odp)) >> umem_odp->page_shift;
- dma = umem_odp->dma_list[idx];

if (!(umem_odp->pfn_list[pfn_idx] & HMM_PFN_VALID))
continue;
if (!(umem_odp->pfn_list[pfn_idx] & HMM_PFN_STICKY))
continue;

- ib_dma_unmap_page(dev, dma, BIT(umem_odp->page_shift),
- DMA_BIDIRECTIONAL);
+ ib_dma_unlink_range(dev, &umem_odp->iova,
+ idx * (1 << umem_odp->page_shift));
if (umem_odp->pfn_list[pfn_idx] & HMM_PFN_WRITE) {
struct page *head_page = compound_head(page);
/*
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 5713fe25f4de..13d61f1ab40b 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -149,6 +149,7 @@ static void populate_mtt(__be64 *pas, size_t idx, size_t nentries,
{
struct ib_umem_odp *odp = to_ib_umem_odp(mr->umem);
bool downgrade = flags & MLX5_IB_UPD_XLT_DOWNGRADE;
+ struct ib_device *dev = odp->umem.ibdev;
unsigned long pfn;
dma_addr_t pa;
size_t i;
@@ -162,12 +163,31 @@ static void populate_mtt(__be64 *pas, size_t idx, size_t nentries,
/* Initial ODP init */
continue;

- pa = odp->dma_list[idx + i];
+ if (pfn & HMM_PFN_STICKY && odp->iova.addr)
+ /*
+ * We are in this flow when there is a need to resync flags,
+ * for example when page was already linked in prefetch call
+ * with READ flag and now we need to add WRITE flag
+ *
+ * This page was already programmed to HW and we don't want/need
+ * to unlink and link it again just to resync flags.
+ *
+ * The DMA address calculation below is based on the fact that
+ * RDMA UMEM doesn't work with swiotlb.
+ */
+ pa = odp->iova.addr + (idx + i) * (1 << odp->page_shift);
+ else
+ pa = ib_dma_link_range(dev, hmm_pfn_to_page(pfn), 0, &odp->iova,
+ (idx + i) * (1 << odp->page_shift));
+ WARN_ON_ONCE(ib_dma_mapping_error(dev, pa));
+
pa |= MLX5_IB_MTT_READ;
if ((pfn & HMM_PFN_WRITE) && !downgrade)
pa |= MLX5_IB_MTT_WRITE;

pas[i] = cpu_to_be64(pa);
+ odp->pfn_list[idx + i] |= HMM_PFN_STICKY;
+ odp->npages++;
}
}

diff --git a/include/rdma/ib_umem_odp.h b/include/rdma/ib_umem_odp.h
index 095b1297cfb1..a786556c65f9 100644
--- a/include/rdma/ib_umem_odp.h
+++ b/include/rdma/ib_umem_odp.h
@@ -17,15 +17,9 @@ struct ib_umem_odp {
/* An array of the pfns included in the on-demand paging umem. */
unsigned long *pfn_list;

- /*
- * An array with DMA addresses mapped for pfns in pfn_list.
- * The lower two bits designate access permissions.
- * See ODP_READ_ALLOWED_BIT and ODP_WRITE_ALLOWED_BIT.
- */
- dma_addr_t *dma_list;
struct dma_iova_attrs iova;
/*
- * The umem_mutex protects the page_list and dma_list fields of an ODP
+ * The umem_mutex protects the page_list field of an ODP
* umem, allowing only a single thread to map/unmap pages. The mutex
* also protects access to the mmu notifier counters.
*/
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index e71fa19187cc..c9e2bcd5268a 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -4160,6 +4160,42 @@ static inline void ib_dma_unmap_page(struct ib_device *dev,
dma_unmap_page(dev->dma_device, addr, size, direction);
}

+/**
+ * ib_dma_link_range - Link a physical page to DMA address
+ * @dev: The device for which the dma_addr is to be created
+ * @page: The page to be mapped
+ * @offset: The offset within the page
+ * @iova: Preallocated IOVA attributes
+ * @dma_offset: DMA offset
+ */
+static inline dma_addr_t ib_dma_link_range(struct ib_device *dev,
+ struct page *page,
+ unsigned long offset,
+ struct dma_iova_attrs *iova,
+ dma_addr_t dma_offset)
+{
+ if (ib_uses_virt_dma(dev))
+ return (uintptr_t)(page_address(page) + offset);
+
+ return dma_link_range(page, offset, iova, dma_offset);
+}
+
+/**
+ * ib_dma_unlink_range - Unlink a mapping created by ib_dma_link_page()
+ * @dev: The device for which the DMA address was created
+ * @iova: DMA IOVA properties
+ * @dma_offset: DMA offset
+ */
+static inline void ib_dma_unlink_range(struct ib_device *dev,
+ struct dma_iova_attrs *iova,
+ dma_addr_t dma_offset)
+{
+ if (ib_uses_virt_dma(dev))
+ return;
+
+ dma_unlink_range(iova, dma_offset);
+}
+
int ib_dma_virt_map_sg(struct ib_device *dev, struct scatterlist *sg, int nents);
static inline int ib_dma_map_sg_attrs(struct ib_device *dev,
struct scatterlist *sg, int nents,
--
2.44.0