vfio/mlx5: Enforce PRE_COPY support

Enable live migration only once the firmware supports PRE_COPY.

PRE_COPY has been supported by the firmware for a long time already [1]
and is required to achieve a low downtime upon live migration.

This lets us clean up some old code that is not applicable those days
while PRE_COPY is fully supported by the firmware.

[1] The minimum firmware version that supports PRE_COPY is 28.36.1010,
it was released in January 2023.

No firmware without PRE_COPY support ever available to users.

Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20240306105624.114830-1-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

3 files changed, 71 insertions, 127 deletions

diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
index c54bcd5d0917..41a4b0cf4297 100644
--- a/drivers/vfio/pci/mlx5/cmd.c
+++ b/drivers/vfio/pci/mlx5/cmd.c
@@ -233,6 +233,10 @@ void mlx5vf_cmd_set_migratable(struct mlx5vf_pci_core_device *mvdev,
 	if (!MLX5_CAP_GEN(mvdev->mdev, migration))
 		goto end;
 
+	if (!(MLX5_CAP_GEN_2(mvdev->mdev, migration_multi_load) &&
+	      MLX5_CAP_GEN_2(mvdev->mdev, migration_tracking_state)))
+		goto end;
+
 	mvdev->vf_id = pci_iov_vf_id(pdev);
 	if (mvdev->vf_id < 0)
 		goto end;
@@ -262,17 +266,14 @@ void mlx5vf_cmd_set_migratable(struct mlx5vf_pci_core_device *mvdev,
 	mvdev->migrate_cap = 1;
 	mvdev->core_device.vdev.migration_flags =
 		VFIO_MIGRATION_STOP_COPY |
-		VFIO_MIGRATION_P2P;
+		VFIO_MIGRATION_P2P |
+		VFIO_MIGRATION_PRE_COPY;
+
 	mvdev->core_device.vdev.mig_ops = mig_ops;
 	init_completion(&mvdev->tracker_comp);
 	if (MLX5_CAP_GEN(mvdev->mdev, adv_virtualization))
 		mvdev->core_device.vdev.log_ops = log_ops;
 
-	if (MLX5_CAP_GEN_2(mvdev->mdev, migration_multi_load) &&
-	    MLX5_CAP_GEN_2(mvdev->mdev, migration_tracking_state))
-		mvdev->core_device.vdev.migration_flags |=
-			VFIO_MIGRATION_PRE_COPY;
-
 	if (MLX5_CAP_GEN_2(mvdev->mdev, migration_in_chunks))
 		mvdev->chunk_mode = 1;
 
@@ -414,6 +415,50 @@ void mlx5vf_free_data_buffer(struct mlx5_vhca_data_buffer *buf)
 	kfree(buf);
 }
 
+static int mlx5vf_add_migration_pages(struct mlx5_vhca_data_buffer *buf,
+				      unsigned int npages)
+{
+	unsigned int to_alloc = npages;
+	struct page **page_list;
+	unsigned long filled;
+	unsigned int to_fill;
+	int ret;
+
+	to_fill = min_t(unsigned int, npages, PAGE_SIZE / sizeof(*page_list));
+	page_list = kvzalloc(to_fill * sizeof(*page_list), GFP_KERNEL_ACCOUNT);
+	if (!page_list)
+		return -ENOMEM;
+
+	do {
+		filled = alloc_pages_bulk_array(GFP_KERNEL_ACCOUNT, to_fill,
+						page_list);
+		if (!filled) {
+			ret = -ENOMEM;
+			goto err;
+		}
+		to_alloc -= filled;
+		ret = sg_alloc_append_table_from_pages(
+			&buf->table, page_list, filled, 0,
+			filled << PAGE_SHIFT, UINT_MAX, SG_MAX_SINGLE_ALLOC,
+			GFP_KERNEL_ACCOUNT);
+
+		if (ret)
+			goto err;
+		buf->allocated_length += filled * PAGE_SIZE;
+		/* clean input for another bulk allocation */
+		memset(page_list, 0, filled * sizeof(*page_list));
+		to_fill = min_t(unsigned int, to_alloc,
+				PAGE_SIZE / sizeof(*page_list));
+	} while (to_alloc > 0);
+
+	kvfree(page_list);
+	return 0;
+
+err:
+	kvfree(page_list);
+	return ret;
+}
+
 struct mlx5_vhca_data_buffer *
 mlx5vf_alloc_data_buffer(struct mlx5_vf_migration_file *migf,
 			 size_t length,
@@ -680,22 +725,20 @@ int mlx5vf_cmd_save_vhca_state(struct mlx5vf_pci_core_device *mvdev,
 		goto err_out;
 	}
 
-	if (MLX5VF_PRE_COPY_SUPP(mvdev)) {
-		if (async_data->stop_copy_chunk) {
-			u8 header_idx = buf->stop_copy_chunk_num ?
-				buf->stop_copy_chunk_num - 1 : 0;
+	if (async_data->stop_copy_chunk) {
+		u8 header_idx = buf->stop_copy_chunk_num ?
+			buf->stop_copy_chunk_num - 1 : 0;
 
-			header_buf = migf->buf_header[header_idx];
-			migf->buf_header[header_idx] = NULL;
-		}
+		header_buf = migf->buf_header[header_idx];
+		migf->buf_header[header_idx] = NULL;
+	}
 
-		if (!header_buf) {
-			header_buf = mlx5vf_get_data_buffer(migf,
-				sizeof(struct mlx5_vf_migration_header), DMA_NONE);
-			if (IS_ERR(header_buf)) {
-				err = PTR_ERR(header_buf);
-				goto err_free;
-			}
+	if (!header_buf) {
+		header_buf = mlx5vf_get_data_buffer(migf,
+			sizeof(struct mlx5_vf_migration_header), DMA_NONE);
+		if (IS_ERR(header_buf)) {
+			err = PTR_ERR(header_buf);
+			goto err_free;
 		}
 	}
 
diff --git a/drivers/vfio/pci/mlx5/cmd.h b/drivers/vfio/pci/mlx5/cmd.h
index 707393df36c4..df421dc6de04 100644
--- a/drivers/vfio/pci/mlx5/cmd.h
+++ b/drivers/vfio/pci/mlx5/cmd.h
@@ -13,9 +13,6 @@
 #include <linux/mlx5/cq.h>
 #include <linux/mlx5/qp.h>
 
-#define MLX5VF_PRE_COPY_SUPP(mvdev) \
-	((mvdev)->core_device.vdev.migration_flags & VFIO_MIGRATION_PRE_COPY)
-
 enum mlx5_vf_migf_state {
 	MLX5_MIGF_STATE_ERROR = 1,
 	MLX5_MIGF_STATE_PRE_COPY_ERROR,
@@ -25,7 +22,6 @@ enum mlx5_vf_migf_state {
 };
 
 enum mlx5_vf_load_state {
-	MLX5_VF_LOAD_STATE_READ_IMAGE_NO_HEADER,
 	MLX5_VF_LOAD_STATE_READ_HEADER,
 	MLX5_VF_LOAD_STATE_PREP_HEADER_DATA,
 	MLX5_VF_LOAD_STATE_READ_HEADER_DATA,
@@ -228,8 +224,6 @@ struct mlx5_vhca_data_buffer *
 mlx5vf_get_data_buffer(struct mlx5_vf_migration_file *migf,
 		       size_t length, enum dma_data_direction dma_dir);
 void mlx5vf_put_data_buffer(struct mlx5_vhca_data_buffer *buf);
-int mlx5vf_add_migration_pages(struct mlx5_vhca_data_buffer *buf,
-			       unsigned int npages);
 struct page *mlx5vf_get_migration_page(struct mlx5_vhca_data_buffer *buf,
 				       unsigned long offset);
 void mlx5vf_state_mutex_unlock(struct mlx5vf_pci_core_device *mvdev);
diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
index 3982fcf60cf2..61d9b0f9146d 100644
--- a/drivers/vfio/pci/mlx5/main.c
+++ b/drivers/vfio/pci/mlx5/main.c
@@ -65,50 +65,6 @@ mlx5vf_get_migration_page(struct mlx5_vhca_data_buffer *buf,
 	return NULL;
 }
 
-int mlx5vf_add_migration_pages(struct mlx5_vhca_data_buffer *buf,
-			       unsigned int npages)
-{
-	unsigned int to_alloc = npages;
-	struct page **page_list;
-	unsigned long filled;
-	unsigned int to_fill;
-	int ret;
-
-	to_fill = min_t(unsigned int, npages, PAGE_SIZE / sizeof(*page_list));
-	page_list = kvzalloc(to_fill * sizeof(*page_list), GFP_KERNEL_ACCOUNT);
-	if (!page_list)
-		return -ENOMEM;
-
-	do {
-		filled = alloc_pages_bulk_array(GFP_KERNEL_ACCOUNT, to_fill,
-						page_list);
-		if (!filled) {
-			ret = -ENOMEM;
-			goto err;
-		}
-		to_alloc -= filled;
-		ret = sg_alloc_append_table_from_pages(
-			&buf->table, page_list, filled, 0,
-			filled << PAGE_SHIFT, UINT_MAX, SG_MAX_SINGLE_ALLOC,
-			GFP_KERNEL_ACCOUNT);
-
-		if (ret)
-			goto err;
-		buf->allocated_length += filled * PAGE_SIZE;
-		/* clean input for another bulk allocation */
-		memset(page_list, 0, filled * sizeof(*page_list));
-		to_fill = min_t(unsigned int, to_alloc,
-				PAGE_SIZE / sizeof(*page_list));
-	} while (to_alloc > 0);
-
-	kvfree(page_list);
-	return 0;
-
-err:
-	kvfree(page_list);
-	return ret;
-}
-
 static void mlx5vf_disable_fd(struct mlx5_vf_migration_file *migf)
 {
 	mutex_lock(&migf->lock);
@@ -777,36 +733,6 @@ mlx5vf_append_page_to_mig_buf(struct mlx5_vhca_data_buffer *vhca_buf,
 	return 0;
 }
 
-static int
-mlx5vf_resume_read_image_no_header(struct mlx5_vhca_data_buffer *vhca_buf,
-				   loff_t requested_length,
-				   const char __user **buf, size_t *len,
-				   loff_t *pos, ssize_t *done)
-{
-	int ret;
-
-	if (requested_length > MAX_LOAD_SIZE)
-		return -ENOMEM;
-
-	if (vhca_buf->allocated_length < requested_length) {
-		ret = mlx5vf_add_migration_pages(
-			vhca_buf,
-			DIV_ROUND_UP(requested_length - vhca_buf->allocated_length,
-				     PAGE_SIZE));
-		if (ret)
-			return ret;
-	}
-
-	while (*len) {
-		ret = mlx5vf_append_page_to_mig_buf(vhca_buf, buf, len, pos,
-						    done);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
-}
-
 static ssize_t
 mlx5vf_resume_read_image(struct mlx5_vf_migration_file *migf,
 			 struct mlx5_vhca_data_buffer *vhca_buf,
@@ -1038,13 +964,6 @@ static ssize_t mlx5vf_resume_write(struct file *filp, const char __user *buf,
 			migf->load_state = MLX5_VF_LOAD_STATE_READ_IMAGE;
 			break;
 		}
-		case MLX5_VF_LOAD_STATE_READ_IMAGE_NO_HEADER:
-			ret = mlx5vf_resume_read_image_no_header(vhca_buf,
-						requested_length,
-						&buf, &len, pos, &done);
-			if (ret)
-				goto out_unlock;
-			break;
 		case MLX5_VF_LOAD_STATE_READ_IMAGE:
 			ret = mlx5vf_resume_read_image(migf, vhca_buf,
 						migf->record_size,
@@ -1114,21 +1033,16 @@ mlx5vf_pci_resume_device_data(struct mlx5vf_pci_core_device *mvdev)
 	}
 
 	migf->buf[0] = buf;
-	if (MLX5VF_PRE_COPY_SUPP(mvdev)) {
-		buf = mlx5vf_alloc_data_buffer(migf,
-			sizeof(struct mlx5_vf_migration_header), DMA_NONE);
-		if (IS_ERR(buf)) {
-			ret = PTR_ERR(buf);
-			goto out_buf;
-		}
-
-		migf->buf_header[0] = buf;
-		migf->load_state = MLX5_VF_LOAD_STATE_READ_HEADER;
-	} else {
-		/* Initial state will be to read the image */
-		migf->load_state = MLX5_VF_LOAD_STATE_READ_IMAGE_NO_HEADER;
+	buf = mlx5vf_alloc_data_buffer(migf,
+		sizeof(struct mlx5_vf_migration_header), DMA_NONE);
+	if (IS_ERR(buf)) {
+		ret = PTR_ERR(buf);
+		goto out_buf;
 	}
 
+	migf->buf_header[0] = buf;
+	migf->load_state = MLX5_VF_LOAD_STATE_READ_HEADER;
+
 	stream_open(migf->filp->f_inode, migf->filp);
 	mutex_init(&migf->lock);
 	INIT_LIST_HEAD(&migf->buf_list);
@@ -1262,13 +1176,6 @@ mlx5vf_pci_step_device_state_locked(struct mlx5vf_pci_core_device *mvdev,
 	}
 
 	if (cur == VFIO_DEVICE_STATE_RESUMING && new == VFIO_DEVICE_STATE_STOP) {
-		if (!MLX5VF_PRE_COPY_SUPP(mvdev)) {
-			ret = mlx5vf_cmd_load_vhca_state(mvdev,
-							 mvdev->resuming_migf,
-							 mvdev->resuming_migf->buf[0]);
-			if (ret)
-				return ERR_PTR(ret);
-		}
 		mlx5vf_disable_fds(mvdev, NULL);
 		return NULL;
 	}