Re: [PATCH V3 3/3] nvme-multipath: enable PCI P2PDMA for multipath devices

Nitesh Shetty
2026-04-17T10:47:01Z

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On 16/04/26 02:26PM, Chaitanya Kulkarni wrote:
>From: Kiran Kumar Modukuri <kmodukuri@nvidia.com>
>
>NVMe multipath does not expose BLK_FEAT_PCI_P2PDMA on the head disk
>even when all underlying controllers support it.
>
>Set BLK_FEAT_PCI_P2PDMA unconditionally in nvme_mpath_alloc_disk()
>alongside the other features. nvme_update_ns_info_block() already
>calls queue_limits_stack_bdev() to stack each path's limits onto the
>head disk, which routes through blk_stack_limits(). The core now
>clears BLK_FEAT_PCI_P2PDMA automatically if any path (e.g., FC) does
>not support it, consistent with how BLK_FEAT_NOWAIT and BLK_FEAT_POLL
>are handled.
>
>Signed-off-by: Kiran Kumar Modukuri <kmodukuri@nvidia.com>
>Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
>---
> drivers/nvme/host/multipath.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
>index ba00f0b72b85..957e39c4795d 100644
>--- a/drivers/nvme/host/multipath.c
>+++ b/drivers/nvme/host/multipath.c
>@@ -734,7 +734,7 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
> blk_set_stacking_limits(&lim);
> lim.dma_alignment = 3;
> lim.features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT |
>- BLK_FEAT_POLL | BLK_FEAT_ATOMIC_WRITES;
>+ BLK_FEAT_POLL | BLK_FEAT_ATOMIC_WRITES | BLK_FEAT_PCI_P2PDMA;
> if (head->ids.csi == NVME_CSI_ZNS)
> lim.features |= BLK_FEAT_ZONED;

Reviewed-by: Nitesh Shetty <nj.shetty@samsung.com>

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