From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D095D298CAF for ; Sun, 11 Oct 2026 13:28:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791725296; cv=none; b=ruFgZTcbPTtLzoobTo59GNCdoOEbn3Wlr2ncpRXjNL8+m5ZXwGgoM3VhrMVUb0Y+JiVM13nd5Sg6duoLdJp8l+ExYH4XjqUQ/bF1047+suX8Ic+OUUeQ+JwW80sLCItI48AcaobDuKdybmyBtHlcEnujxG9/XiYgS8rWFmEbkKI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791725296; c=relaxed/simple; bh=nlaL8FdcWvuRbcdj/4SiWgiaUgVt9qQihO64oW0Mi5M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=edJLMgP0l5hy2nxQ1D6Vy7Z+e2IofIjX+Uyyvi+HZS3il0YE/jWgcRCEvIJ+YqOsGdmbI7eP8xTmulstWOA1vEBUs/xs4FBY9TfmtLoHzM0XsvjHU/sPdkIQ6RF0wqoJBybF5BYJhMyOO1KP3+jdZ6P9v263wnJT1BeNuFO7Wu8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=edK90Ost; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="edK90Ost" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E6A1C1F0089B; Sun, 11 Oct 2026 13:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791725295; bh=OvRMSZygGKtmtgsmxGPP5+Lft50z8l7l7YxAjw3XvNQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=edK90Ost/IAR6ElOA7BerYhmUggyFBcKH0ZvPZSsh8bEmrZBWIJbXkSXPvkyc9ejz /aEnF48uOEfarMrG0L9N35F9SHVIjPqJvaFkSAQQ+1/GZK6IwL/WFRekq62NsPRWJc GpT3rvxfsHA7oVDZH7zmUnJZmVO0wURs1MuzHEmlAMixk3b2Q4G57YJQBrz1AZJhXs 9mCBcZmVd/v7/74OjYZwvBZxwzTC+DL6ClhifgoFwLN+Xwp58NtrHUQDk0QW9q3ZtU fUsNK1R5TPEmmTZDuNABLYE2NuvJl9i1+yRt8Byz9GtOhwthIVmQUan1rZpp6frT08 no2j2GwTSR4FA== Date: Sun, 11 Oct 2026 16:28:10 +0300 From: Leon Romanovsky To: Michael Margolin Cc: Jason Gunthorpe , Yonatan Nachum , linux-rdma@vger.kernel.org, sleybo@amazon.com, matua@amazon.com, gal.pressman@linux.dev, Yehuda Yitschak Subject: Re: [PATCH for-next] RDMA/efa: Expose device P2P DMA support via device query Message-ID: <20261011132810.GD27033@unreal> References: <20260923163830.GA6954@dev-dsk-mrgolin-1c-b2091117.eu-west-1.amazon.com> <20260923171741.GH2545495@nvidia.com> <20260924152913.GB24800@dev-dsk-mrgolin-1c-b2091117.eu-west-1.amazon.com> <20260924182201.GB9354@nvidia.com> <20260924193026.GA13498@dev-dsk-mrgolin-1c-b2091117.eu-west-1.amazon.com> <20260925125512.GM9354@nvidia.com> <20260930132613.GA24387@dev-dsk-mrgolin-1c-b2091117.eu-west-1.amazon.com> <20261001155333.GP3401365@unreal> <20261002145241.GV1616761@nvidia.com> <20261007090136.GA35552@dev-dsk-mrgolin-1c-b2091117.eu-west-1.amazon.com> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20261007090136.GA35552@dev-dsk-mrgolin-1c-b2091117.eu-west-1.amazon.com> On Wed, Oct 07, 2026 at 09:01:36AM +0000, Michael Margolin wrote: > On Fri, Oct 02, 2026 at 11:52:41AM -0300, Jason Gunthorpe wrote: > > On Thu, Oct 01, 2026 at 06:53:33PM +0300, Leon Romanovsky wrote: > > > > > > Looked at Leon's patches and it does seem like the right place to expose > > > > such peer relations. Although it wouldn't help with our immediate need, > > > > maybe we can add a sysfs interface on top of Leon's patches to expose > > > > the gathered accessiblity (and maybe also performance) information. > > > > > > > > Leon, what is your opinion on this? > > > > > > ACPI tables are available here /sys/firmware/acpi/tables/, this will > > > include our new p2p HMAT extension. > > I was iterating over Jason's idea and what I imagine is an interface > that contains already parsed data at PCI level, like: > > /sys/firmware/acpi/p2p/ > ├── 0000:55:00.0/ # RDMA NIC > │ ├── 0000:59:00.0/ # → GPU (reachable peer) > │ │ ├── latency_ns # 200 > │ │ └── bandwidth_mbs # 32000 > │ └── 0000:5a:00.0/ # → GPU (reachable peer) > │ ├── latency_ns # 200 > │ └── bandwidth_mbs # 32000 > │ > ├── 0000:59:00.0/ # GPU > │ ├── 0000:55:00.0/ # → RDMA NIC (reachable peer) > │ │ ├── latency_ns # 200 > │ │ └── bandwidth_mbs # 32000 > │ └── 0000:56:00.0/ # → RDMA NIC (reachable peer) > │ ├── latency_ns # 200 > │ └── bandwidth_mbs # 32000 > │ > ├── 0000:9a:00.0/ # NVMe > │ └── 0000:55:00.0/ # → RDMA NIC (reachable peer) > │ ├── latency_ns # 300 > │ └── bandwidth_mbs # 12000 I'm afraid that writing and maintaining an in-kernel parser that creates a matrix of non-racy symlinks to point to right PCI BDF will be quite painful. Thanks