[RFC 14/16] vfio/mlx5: Convert vfio to use DMA link API

Leon Romanovsky
2024-03-05T13:35:18Z

Remove intermediate scatter-gather table as it is not needed
if DMA link API is used. This conversion reduces drastically
the memory used to manage that table.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
drivers/vfio/pci/mlx5/cmd.c | 177 ++++++++++++++++-------------------
drivers/vfio/pci/mlx5/cmd.h | 8 +-
drivers/vfio/pci/mlx5/main.c | 50 ++--------
3 files changed, 91 insertions(+), 144 deletions(-)

diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
index 5e2103042d9b..cfae03f7b7da 100644
--- a/drivers/vfio/pci/mlx5/cmd.c
+++ b/drivers/vfio/pci/mlx5/cmd.c
@@ -332,26 +332,60 @@ static u32 *alloc_mkey_in(u32 npages, u32 pdn)
return in;
}

-static int create_mkey(struct mlx5_core_dev *mdev, u32 npages,
- struct mlx5_vhca_data_buffer *buf, u32 *mkey_in,
+static int create_mkey(struct mlx5_core_dev *mdev, u32 npages, u32 *mkey_in,
u32 *mkey)
{
+ int inlen = MLX5_ST_SZ_BYTES(create_mkey_in) +
+ sizeof(__be64) * round_up(npages, 2);
+
+ return mlx5_core_create_mkey(mdev, mkey, mkey_in, inlen);
+}
+
+static void unregister_dma_pages(struct mlx5_core_dev *mdev, u32 npages,
+ u32 *mkey_in, struct dma_iova_attrs *iova)
+{
+ dma_addr_t addr;
__be64 *mtt;
- int inlen;
+ int i;

mtt = (__be64 *)MLX5_ADDR_OF(create_mkey_in, mkey_in, klm_pas_mtt);

- if (buf) {
- struct sg_dma_page_iter dma_iter;
+ for (i = npages - 1; i >= 0; i--) {
+ addr = be64_to_cpu(mtt[i]);
+ dma_unlink_range(iova, addr);
+ }
+ dma_free_iova(iova);
+}
+
+static int register_dma_pages(struct mlx5_core_dev *mdev, u32 npages,
+ struct page **page_list, u32 *mkey_in,
+ struct dma_iova_attrs *iova)
+{
+ dma_addr_t addr;
+ __be64 *mtt;
+ int i, err;
+
+ iova->dev = mdev->device;
+ iova->size = npages * PAGE_SIZE;
+ err = dma_alloc_iova(iova);
+ if (err)
+ return err;
+
+ mtt = (__be64 *)MLX5_ADDR_OF(create_mkey_in, mkey_in, klm_pas_mtt);
+
+ for (i = 0; i < npages; i++) {
+ addr = dma_link_range(page_list[i], 0, iova, i * PAGE_SIZE);
+ if (dma_mapping_error(mdev->device, addr))
+ goto error;

- for_each_sgtable_dma_page(&buf->table.sgt, &dma_iter, 0)
- *mtt++ = cpu_to_be64(sg_page_iter_dma_address(&dma_iter));
+ *mtt++ = cpu_to_be64(addr);
}

- inlen = MLX5_ST_SZ_BYTES(create_mkey_in) +
- sizeof(__be64) * round_up(npages, 2);
+ return 0;

- return mlx5_core_create_mkey(mdev, mkey, mkey_in, inlen);
+error:
+ unregister_dma_pages(mdev, i, mkey_in, iova);
+ return -ENOMEM;
}

static int mlx5vf_dma_data_buffer(struct mlx5_vhca_data_buffer *buf)
@@ -367,17 +401,16 @@ static int mlx5vf_dma_data_buffer(struct mlx5_vhca_data_buffer *buf)
if (buf->dmaed || !buf->npages)
return -EINVAL;

- ret = dma_map_sgtable(mdev->device, &buf->table.sgt, buf->dma_dir, 0);
- if (ret)
- return ret;
-
buf->mkey_in = alloc_mkey_in(buf->npages, buf->migf->pdn);
- if (!buf->mkey_in) {
- ret = -ENOMEM;
- goto err;
- }
+ if (!buf->mkey_in)
+ return -ENOMEM;
+
+ ret = register_dma_pages(mdev, buf->npages, buf->page_list,
+ buf->mkey_in, &buf->iova);
+ if (ret)
+ goto err_register_dma;

- ret = create_mkey(mdev, buf->npages, buf, buf->mkey_in, &buf->mkey);
+ ret = create_mkey(mdev, buf->npages, buf->mkey_in, &buf->mkey);
if (ret)
goto err_create_mkey;

@@ -386,32 +419,39 @@ static int mlx5vf_dma_data_buffer(struct mlx5_vhca_data_buffer *buf)
return 0;

err_create_mkey:
+ unregister_dma_pages(mdev, buf->npages, buf->mkey_in, &buf->iova);
+err_register_dma:
kvfree(buf->mkey_in);
-err:
- dma_unmap_sgtable(mdev->device, &buf->table.sgt, buf->dma_dir, 0);
return ret;
}

+static void free_page_list(u32 npages, struct page **page_list)
+{
+ int i;
+
+ /* Undo alloc_pages_bulk_array() */
+ for (i = npages - 1; i >= 0; i--)
+ __free_page(page_list[i]);
+
+ kvfree(page_list);
+}
+
void mlx5vf_free_data_buffer(struct mlx5_vhca_data_buffer *buf)
{
- struct mlx5_vf_migration_file *migf = buf->migf;
- struct sg_page_iter sg_iter;
+ struct mlx5vf_pci_core_device *mvdev = buf->migf->mvdev;
+ struct mlx5_core_dev *mdev = mvdev->mdev;

- lockdep_assert_held(&migf->mvdev->state_mutex);
- WARN_ON(migf->mvdev->mdev_detach);
+ lockdep_assert_held(&mvdev->state_mutex);
+ WARN_ON(mvdev->mdev_detach);

if (buf->dmaed) {
- mlx5_core_destroy_mkey(migf->mvdev->mdev, buf->mkey);
+ mlx5_core_destroy_mkey(mdev, buf->mkey);
+ unregister_dma_pages(mdev, buf->npages, buf->mkey_in,
+ &buf->iova);
kvfree(buf->mkey_in);
- dma_unmap_sgtable(migf->mvdev->mdev->device, &buf->table.sgt,
- buf->dma_dir, 0);
}

- /* Undo alloc_pages_bulk_array() */
- for_each_sgtable_page(&buf->table.sgt, &sg_iter, 0)
- __free_page(sg_page_iter_page(&sg_iter));
- sg_free_append_table(&buf->table);
- kvfree(buf->page_list);
+ free_page_list(buf->npages, buf->page_list);
kfree(buf);
}

@@ -426,7 +466,7 @@ mlx5vf_alloc_data_buffer(struct mlx5_vf_migration_file *migf, u32 npages,
if (!buf)
return ERR_PTR(-ENOMEM);

- buf->dma_dir = dma_dir;
+ buf->iova.dir = dma_dir;
buf->migf = migf;
if (npages) {
ret = mlx5vf_add_migration_pages(buf, npages);
@@ -469,7 +509,7 @@ mlx5vf_get_data_buffer(struct mlx5_vf_migration_file *migf, u32 npages,

spin_lock_irq(&migf->list_lock);
list_for_each_entry_safe(buf, temp_buf, &migf->avail_list, buf_elm) {
- if (buf->dma_dir == dma_dir) {
+ if (buf->iova.dir == dma_dir) {
list_del_init(&buf->buf_elm);
if (buf->npages >= npages) {
spin_unlock_irq(&migf->list_lock);
@@ -1253,17 +1293,6 @@ static void mlx5vf_destroy_qp(struct mlx5_core_dev *mdev,
kfree(qp);
}

-static void free_recv_pages(struct mlx5_vhca_recv_buf *recv_buf)
-{
- int i;
-
- /* Undo alloc_pages_bulk_array() */
- for (i = 0; i < recv_buf->npages; i++)
- __free_page(recv_buf->page_list[i]);
-
- kvfree(recv_buf->page_list);
-}
-
static int alloc_recv_pages(struct mlx5_vhca_recv_buf *recv_buf,
unsigned int npages)
{
@@ -1300,56 +1329,16 @@ static int alloc_recv_pages(struct mlx5_vhca_recv_buf *recv_buf,
return -ENOMEM;
}

-static void unregister_dma_pages(struct mlx5_core_dev *mdev, u32 npages,
- u32 *mkey_in)
-{
- dma_addr_t addr;
- __be64 *mtt;
- int i;
-
- mtt = (__be64 *)MLX5_ADDR_OF(create_mkey_in, mkey_in, klm_pas_mtt);
-
- for (i = npages - 1; i >= 0; i--) {
- addr = be64_to_cpu(mtt[i]);
- dma_unmap_single(mdev->device, addr, PAGE_SIZE,
- DMA_FROM_DEVICE);
- }
-}
-
-static int register_dma_pages(struct mlx5_core_dev *mdev, u32 npages,
- struct page **page_list, u32 *mkey_in)
-{
- dma_addr_t addr;
- __be64 *mtt;
- int i;
-
- mtt = (__be64 *)MLX5_ADDR_OF(create_mkey_in, mkey_in, klm_pas_mtt);
-
- for (i = 0; i < npages; i++) {
- addr = dma_map_page(mdev->device, page_list[i], 0, PAGE_SIZE,
- DMA_FROM_DEVICE);
- if (dma_mapping_error(mdev->device, addr))
- goto error;
-
- *mtt++ = cpu_to_be64(addr);
- }
-
- return 0;
-
-error:
- unregister_dma_pages(mdev, i, mkey_in);
- return -ENOMEM;
-}
-
static void mlx5vf_free_qp_recv_resources(struct mlx5_core_dev *mdev,
struct mlx5_vhca_qp *qp)
{
struct mlx5_vhca_recv_buf *recv_buf = &qp->recv_buf;

mlx5_core_destroy_mkey(mdev, recv_buf->mkey);
- unregister_dma_pages(mdev, recv_buf->npages, recv_buf->mkey_in);
+ unregister_dma_pages(mdev, recv_buf->npages, recv_buf->mkey_in,
+ &recv_buf->iova);
kvfree(recv_buf->mkey_in);
- free_recv_pages(&qp->recv_buf);
+ free_page_list(recv_buf->npages, recv_buf->page_list);
}

static int mlx5vf_alloc_qp_recv_resources(struct mlx5_core_dev *mdev,
@@ -1370,24 +1359,24 @@ static int mlx5vf_alloc_qp_recv_resources(struct mlx5_core_dev *mdev,
goto end;
}

+ recv_buf->iova.dir = DMA_FROM_DEVICE;
err = register_dma_pages(mdev, npages, recv_buf->page_list,
- recv_buf->mkey_in);
+ recv_buf->mkey_in, &recv_buf->iova);
if (err)
goto err_register_dma;

- err = create_mkey(mdev, npages, NULL, recv_buf->mkey_in,
- &recv_buf->mkey);
+ err = create_mkey(mdev, npages, recv_buf->mkey_in, &recv_buf->mkey);
if (err)
goto err_create_mkey;

return 0;

err_create_mkey:
- unregister_dma_pages(mdev, npages, recv_buf->mkey_in);
+ unregister_dma_pages(mdev, npages, recv_buf->mkey_in, &recv_buf->iova);
err_register_dma:
kvfree(recv_buf->mkey_in);
end:
- free_recv_pages(recv_buf);
+ free_page_list(npages, recv_buf->page_list);
return err;
}

diff --git a/drivers/vfio/pci/mlx5/cmd.h b/drivers/vfio/pci/mlx5/cmd.h
index 815fcb54494d..3a046166d9f2 100644
--- a/drivers/vfio/pci/mlx5/cmd.h
+++ b/drivers/vfio/pci/mlx5/cmd.h
@@ -57,22 +57,17 @@ struct mlx5_vf_migration_header {
};

struct mlx5_vhca_data_buffer {
+ struct dma_iova_attrs iova;
struct page **page_list;
- struct sg_append_table table;
loff_t start_pos;
u64 length;
u32 npages;
u32 mkey;
u32 *mkey_in;
- enum dma_data_direction dma_dir;
u8 dmaed:1;
u8 stop_copy_chunk_num;
struct list_head buf_elm;
struct mlx5_vf_migration_file *migf;
- /* Optimize mlx5vf_get_migration_page() for sequential access */
- struct scatterlist *last_offset_sg;
- unsigned int sg_last_entry;
- unsigned long last_offset;
};

struct mlx5vf_async_data {
@@ -137,6 +132,7 @@ struct mlx5_vhca_cq {
};

struct mlx5_vhca_recv_buf {
+ struct dma_iova_attrs iova;
u32 npages;
struct page **page_list;
u32 next_rq_offset;
diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
index 7ffe24693a55..668c28bc429c 100644
--- a/drivers/vfio/pci/mlx5/main.c
+++ b/drivers/vfio/pci/mlx5/main.c
@@ -34,35 +34,10 @@ static struct mlx5vf_pci_core_device *mlx5vf_drvdata(struct pci_dev *pdev)
core_device);
}

-struct page *
-mlx5vf_get_migration_page(struct mlx5_vhca_data_buffer *buf,
- unsigned long offset)
+struct page *mlx5vf_get_migration_page(struct mlx5_vhca_data_buffer *buf,
+ unsigned long offset)
{
- unsigned long cur_offset = 0;
- struct scatterlist *sg;
- unsigned int i;
-
- /* All accesses are sequential */
- if (offset < buf->last_offset || !buf->last_offset_sg) {
- buf->last_offset = 0;
- buf->last_offset_sg = buf->table.sgt.sgl;
- buf->sg_last_entry = 0;
- }
-
- cur_offset = buf->last_offset;
-
- for_each_sg(buf->last_offset_sg, sg,
- buf->table.sgt.orig_nents - buf->sg_last_entry, i) {
- if (offset < sg->length + cur_offset) {
- buf->last_offset_sg = sg;
- buf->sg_last_entry += i;
- buf->last_offset = cur_offset;
- return nth_page(sg_page(sg),
- (offset - cur_offset) / PAGE_SIZE);
- }
- cur_offset += sg->length;
- }
- return NULL;
+ return buf->page_list[offset / PAGE_SIZE];
}

int mlx5vf_add_migration_pages(struct mlx5_vhca_data_buffer *buf,
@@ -72,13 +47,9 @@ int mlx5vf_add_migration_pages(struct mlx5_vhca_data_buffer *buf,
size_t old_size, new_size;
struct page **page_list;
unsigned long filled;
- unsigned int to_fill;
- int ret;

- to_fill = min_t(unsigned int, npages,
- PAGE_SIZE / sizeof(*buf->page_list));
old_size = buf->npages * sizeof(*buf->page_list);
- new_size = old_size + to_fill * sizeof(*buf->page_list);
+ new_size = old_size + to_alloc * sizeof(*buf->page_list);
page_list = kvrealloc(buf->page_list, old_size, new_size,
GFP_KERNEL_ACCOUNT | __GFP_ZERO);
if (!page_list)
@@ -87,22 +58,13 @@ int mlx5vf_add_migration_pages(struct mlx5_vhca_data_buffer *buf,
buf->page_list = page_list;

do {
- filled = alloc_pages_bulk_array(GFP_KERNEL_ACCOUNT, to_fill,
+ filled = alloc_pages_bulk_array(GFP_KERNEL_ACCOUNT, to_alloc,
buf->page_list + buf->npages);
if (!filled)
return -ENOMEM;

to_alloc -= filled;
- ret = sg_alloc_append_table_from_pages(
- &buf->table, buf->page_list + buf->npages, filled, 0,
- filled << PAGE_SHIFT, UINT_MAX, SG_MAX_SINGLE_ALLOC,
- GFP_KERNEL_ACCOUNT);
- if (ret)
- return ret;
-
buf->npages += filled;
- to_fill = min_t(unsigned int, to_alloc,
- PAGE_SIZE / sizeof(*buf->page_list));
} while (to_alloc > 0);

return 0;
@@ -164,7 +126,7 @@ static void mlx5vf_buf_read_done(struct mlx5_vhca_data_buffer *vhca_buf)
struct mlx5_vf_migration_file *migf = vhca_buf->migf;

if (vhca_buf->stop_copy_chunk_num) {
- bool is_header = vhca_buf->dma_dir == DMA_NONE;
+ bool is_header = vhca_buf->iova.dir == DMA_NONE;
u8 chunk_num = vhca_buf->stop_copy_chunk_num;
size_t next_required_umem_size = 0;

--
2.44.0