From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1F533FEC118 for ; Tue, 24 Mar 2026 21:29:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uavJxVJD6COofSIdoLQ9QdM6HmYshFmtHbhL7rFiDYk=; b=Zttd8yt258Az5VJQUYwuKjsITm GPj8h1CaWPr2LCuO/lVA2Is1/Ak+cEnkkfPKI+VC/S4eqo4/CUDRV69vGE43riGjGv4K3qCzg3McW Cixpr8YwfOFf1Q0SCmtK05slBv7jnQPQcFeUwnkfkD264xZqx5Z1OcNB/56JsfVqNPHn0INf3chm7 nWntj7IGxkHac75lku+Au77YtZ4u03HZHs1I5i9IdcpAi6cIUx2cZyy6/ubDBf8vpeR4/T9E6tuxH 44qRj94/oSEqDzOaAnVjeB8BfItESXmVy5ZaQP5tHpRXjEE781haDXXhQs8xaLVcP/ZMMPShIaUp7 vyDElW8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w59Jn-00000002G0q-0ywO; Tue, 24 Mar 2026 21:29:43 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w59Jl-00000002G0O-0Yum for linux-nvme@lists.infradead.org; Tue, 24 Mar 2026 21:29:42 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 117A340200; Tue, 24 Mar 2026 21:29:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6ED46C19424; Tue, 24 Mar 2026 21:29:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774387779; bh=u5/JBwfDXGvNqTWVPuFo0bB9nPHgweRS2A8ofbk3anE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j3n+HMLcWcBDA1xwtxPBKSsyNo7kCRij22d7lJyXjqnX8Oaqqic6ujJogGFevjmR1 EWFjEh/mxxXftRtpUpnnj4UZ6Mz4Wtq1HxQAZSWgn9T2VdrJjtQn1YJY4NmY6AST5x csJOubrm4P7VakSKBb2RtAjjaaTLitu7AgHJ6WFzNaIfBk7Ivv7P3l4NelOM1i6yhd V0dGgy28y/5nZmpJdOue/48fongIqSmzklKbs4NUXxKLU0DGo3jEROuFSw/y5ur0XS rrQyf3JiOdHceDrM4Tf+vvfU7JhLGxvbXK7uhxWy7H8cIyBXxchONECQOZFfaIdW7Y sZJT6BNNWqT3w== Date: Tue, 24 Mar 2026 15:29:37 -0600 From: Keith Busch To: Kiran Modukuri Cc: Christoph Hellwig , Chaitanya Kulkarni , "song@kernel.org" , "yukuai@fnnas.com" , "linan122@huawei.com" , "axboe@kernel.dk" , "sagi@grimberg.me" , "linux-raid@vger.kernel.org" , "linux-nvme@lists.infradead.org" Subject: Re: [PATCH 1/2] md: Add PCI_P2PDMA support for MD RAID volumes Message-ID: References: <20260323234416.46944-1-kch@nvidia.com> <20260323234416.46944-2-kch@nvidia.com> <20260324064816.GA1409@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260324_142941_191193_B79FA30D X-CRM114-Status: GOOD ( 12.43 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org 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.