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[34.124.234.44]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b9caa91671sm115257035ad.13.2026.05.04.14.25.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2026 14:25:47 -0700 (PDT) Date: Mon, 4 May 2026 21:25:41 +0000 From: Pranjal Shrivastava To: Chaitanya Kulkarni Cc: song@kernel.org, yukuai@fnnas.com, linan122@huawei.com, kbusch@kernel.org, axboe@kernel.dk, hch@lst.de, sagi@grimberg.me, linux-raid@vger.kernel.org, linux-nvme@lists.infradead.org, kmodukuri@nvidia.com Subject: Re: [PATCH V3 0/2] md/nvme: Enable PCI P2PDMA support for RAID0 and NVMe Multipath Message-ID: References: <20260416212633.72650-1-kch@nvidia.com> Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260416212633.72650-1-kch@nvidia.com> On Thu, Apr 16, 2026 at 02:26:30PM -0700, Chaitanya Kulkarni wrote: > Hi, > > This patch series extends PCI peer-to-peer DMA (P2PDMA) support to enable > direct data transfers between PCIe devices through RAID and NVMe multipath > block layers. > > Current Linux kernel P2PDMA infrastructure supports direct peer-to-peer > transfers, but this support is not propagated through certain storage > stacks like MD RAID and NVMe multipath. This adds two patches for > MD RAID 0/1/10 and NVMe to propogate P2PDMA support through the > storage stack. > > All four test scenarios demonstrate that P2PDMA capabilities are correctly > propagated through both the MD RAID layer (patch 1/2) and NVMe multipath > layer (patch 2/2). Direct peer-to-peer transfers complete successfully with > full data integrity verification, confirming that: > > 1. RAID devices properly inherit P2PDMA capability from member devices > 2. NVMe multipath devices correctly expose P2PDMA support > 3. P2P memory buffers can be used for transfers involving both types > 4. Data integrity is maintained across all transfer combinations > > I've added the patch specific tests and blktest log as well at the end. > > Repo:- > > git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git > > Branch HEAD:- > > commit 88a57e15861997dd6fa98154ad087f7831bbead1 (origin/for-next) > Merge: 81a0a2e4e535 36446de0c30c > Author: Jens Axboe > Date: Fri Apr 10 07:02:42 2026 -0600 > > Merge branch 'for-7.1/block' into for-next > > * for-7.1/block: > ublk: fix tautological comparison warning in ublk_ctrl_reg_buf > -ck > > Changes from V2:- > > 1. Unconditionally set the BLK_FEAT_PCI_P2PDMA for md and nvme multipath. > (Christoph) > 2. Add a prep patch to diable BLK_FEAT_PCI_P2PDMA in the blk_stack_limit(). > (christoph) > > Changes from V1:- > - Update patch 1 to explicitly support MD RAID 0/1/10. > - Fix signoff chain order for patch 2. > - Clear BLK_FEAT_PCI_P2PDMA in nvme_mpath_add_disk() when a newly > added path does not support it, to handle multipath across different > transports. > - Add nvme multipath test log for mixed transport TCP and PCIe. > > Chaitanya Kulkarni (1): > block: clear BLK_FEAT_PCI_P2PDMA in blk_stack_limits() for > non-supporting devices > > Kiran Kumar Modukuri (2): > md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device > nvme-multipath: enable PCI P2PDMA for multipath devices > > block/blk-settings.c | 2 ++ > drivers/md/raid0.c | 1 + > drivers/md/raid1.c | 1 + > drivers/md/raid10.c | 1 + > drivers/nvme/host/multipath.c | 2 +- > 5 files changed, 6 insertions(+), 1 deletion(-) > Tested with NVMe-oF (RDMA). Tested=by: Pranjal Shrivastava Thanks, Praan