From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 633D735F182 for ; Tue, 24 Mar 2026 21:29:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774387780; cv=none; b=AraZaSb2wRhpWd+sHd4aQUpT6BcS3QDD1pKujJI3AspcY1IU0FIlF489TJYrjM84fPaOjK20McEdrCvttecW3cEsQJGPv/24/ooAiNinNQjs+c1tGrI1FOPcvILFImOQit99TYys9rn98BsnZ02aDoBrD605qINDv58j6r6ViJc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774387780; c=relaxed/simple; bh=u5/JBwfDXGvNqTWVPuFo0bB9nPHgweRS2A8ofbk3anE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Fuk6vP844fszH1IMrmEfYVOrMXi/7V+dMJYkfg7JObjmBhVPwkpi2CtnkGER+udCTa5qoodYQmCW87Q6odniL1e3CRBRlg5+cEjojImcN7fJEa/6pMbq5irbNBf/lK23glgiGh55lbnDfFmEZkafHx4REYfkCMSRzI+Qrb/DnBc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j3n+HMLc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="j3n+HMLc" 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> 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: 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.