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 6B949E98FC2 for ; Thu, 9 Apr 2026 06:27:10 +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=XjnxrByH2GvRBEuNEnFZr53nst0jKv1IcAIuYTn7Ew4=; b=r1MjPvCxzak4WxvrC1azSsQOv9 uFOCGwwBmd8AVFtMd9spE3lwD522yuuGvKjAuJX8AmDPp1DRlC3lPg83S1PuFKYJSgzqxQTYIMA4o O49dx4EKuQdhjmDkvy5eyO51bn/9k12CsJEl4cg4XPn+xasF2/cleNul23b/iRri6TGXTliG9Uu2J xmFzZjlxEh/yvEV7a/wntiMcgwxvuuqlkIA2rdSr0N7ccU5Oy4E2s9PniqNCVDwEaIGOSvCN0xWqL 9Kd6oICcTag1SZxXqJyahb9ghuapkSBoDImobNTFPDOMWGJMiscKYBTcl+wPmynaE0V/uD3CleabL xYIB7Xvw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wAir5-00000009lfp-0CcP; Thu, 09 Apr 2026 06:27:07 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wAir2-00000009lfI-0F7G for linux-nvme@lists.infradead.org; Thu, 09 Apr 2026 06:27:05 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 996B368BFE; Thu, 9 Apr 2026 08:26:59 +0200 (CEST) Date: Thu, 9 Apr 2026 08:26:59 +0200 From: Christoph Hellwig 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 V2 2/2] nvme-multipath: enable PCI P2PDMA for multipath devices Message-ID: <20260409062659.GA7335@lst.de> References: <20260408072537.46540-1-kch@nvidia.com> <20260408072537.46540-3-kch@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260408072537.46540-3-kch@nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260408_232704_243570_2A952950 X-CRM114-Status: GOOD ( 25.58 ) 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 Wed, Apr 08, 2026 at 12:25:37AM -0700, Chaitanya Kulkarni wrote: > From: Kiran Kumar Modukuri > > NVMe multipath does not expose BLK_FEAT_PCI_P2PDMA on the head disk > even when the underlying controller supports it. > > Set BLK_FEAT_PCI_P2PDMA in nvme_mpath_alloc_disk() when the controller > advertises P2PDMA support via ctrl->ops->supports_pci_p2pdma. > > Since multipath can match paths across different transports (e.g. PCIe > and FC), not all paths are guaranteed to support P2PDMA. Clear > BLK_FEAT_PCI_P2PDMA from the head disk in nvme_mpath_add_disk() if the > newly added path does not support it, ensuring the feature is only > advertised when every member supports it. > > Signed-off-by: Kiran Kumar Modukuri > Signed-off-by: Chaitanya Kulkarni > --- > drivers/nvme/host/multipath.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c > index ba00f0b72b85..48d920ce803f 100644 > --- a/drivers/nvme/host/multipath.c > +++ b/drivers/nvme/host/multipath.c > @@ -737,6 +737,9 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head) > BLK_FEAT_POLL | BLK_FEAT_ATOMIC_WRITES; > if (head->ids.csi == NVME_CSI_ZNS) > lim.features |= BLK_FEAT_ZONED; > + if (ctrl->ops && ctrl->ops->supports_pci_p2pdma && > + ctrl->ops->supports_pci_p2pdma(ctrl)) > + lim.features |= BLK_FEAT_PCI_P2PDMA; I think we can just add this unconditionally here, similar to all the other feaures above the ZNS conditional as any non-supporting controller will clear it later. > > void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid) > { > + struct nvme_ns_head *head = ns->head; > + > + /* > + * Clear BLK_FEAT_PCI_P2PDMA on the head disk if this path does not > + * support it. Multipath may span different transports (e.g. PCIe and > + * FC), so every member must support P2PDMA for it to be safe on the > + * head disk. > + */ > + if (head->disk && !blk_queue_pci_p2pdma(ns->queue)) { > + struct queue_limits lim = > + queue_limits_start_update(head->disk->queue); > + lim.features &= ~BLK_FEAT_PCI_P2PDMA; > + queue_limits_commit_update(head->disk->queue, &lim); > + } And this really should go into the core block code in blk_stack_limits, so that BLK_FEAT_PCI_P2PDMA is cleared whenever a non-confirming device is added, similar to BLK_FEAT_NOWAIT and BLK_FEAT_POLL.