From: Keith Busch <kbusch@kernel.org>
To: Kiran Modukuri <kmodukuri@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>,
Chaitanya Kulkarni <kch@nvidia.com>,
"song@kernel.org" <song@kernel.org>,
"yukuai@fnnas.com" <yukuai@fnnas.com>,
"linan122@huawei.com" <linan122@huawei.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"sagi@grimberg.me" <sagi@grimberg.me>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
Subject: Re: [PATCH 1/2] md: Add PCI_P2PDMA support for MD RAID volumes
Date: Tue, 24 Mar 2026 15:29:37 -0600 [thread overview]
Message-ID: <acMCQaEOAqZEfyyT@kbusch-mbp> (raw)
In-Reply-To: <DM4PR12MB8473B3907CAF51AEBAE573E5D548A@DM4PR12MB8473.namprd12.prod.outlook.com>
On Tue, Mar 24, 2026 at 09:13:55PM +0000, Kiran Modukuri wrote:
> Hi Christoph,
>
> We tested with RAID0 , RAID1 and RAID10 only. You're right that parity RAID personalities
> need CPU access to data pages for XOR/parity computation, which won't
> work with P2P mappings.
>
>
> We'll send a v2 that moves BLK_FEAT_PCI_P2PDMA out of
> md_init_stacking_limits() and instead has raid0, raid1 and raid10
> opt in individually during their queue limits setup. raid4/5/6 will
> not set the flag.
I think the parity could work with P2P memory if the calculation is
offloaded to a dma_aysnc_tx. It doesn't look like we necessarily know if
any particular xor is going to get offloaded, though.
next prev parent reply other threads:[~2026-03-24 21:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-23 23:44 [PATCH 0/2] Enable PCI P2PDMA support for RAID0 and NVMe Multipath Chaitanya Kulkarni
2026-03-23 23:44 ` [PATCH 1/2] md: Add PCI_P2PDMA support for MD RAID volumes Chaitanya Kulkarni
2026-03-24 6:48 ` Christoph Hellwig
[not found] ` <DM4PR12MB8473B3907CAF51AEBAE573E5D548A@DM4PR12MB8473.namprd12.prod.outlook.com>
2026-03-24 21:29 ` Keith Busch [this message]
[not found] ` <DM4PR12MB84736C00E876FD160464EB35D548A@DM4PR12MB8473.namprd12.prod.outlook.com>
2026-03-24 22:08 ` Keith Busch
2026-03-23 23:44 ` [PATCH 2/2] nvme-multipath: enable PCI P2PDMA for multipath devices Chaitanya Kulkarni
2026-03-24 6:49 ` Christoph Hellwig
2026-03-24 14:40 ` Keith Busch
2026-03-25 3:50 ` Chaitanya Kulkarni
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