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 E780F42E418; Wed, 26 Aug 2026 14:08:34 +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=1787753316; cv=none; b=RDhVpFk+UTfKDIQTS/ea9SCA3KLebZ5A3aqvn/6Yhi5TOGgc9VpD55lJcGIs4FWnV4rJWy9iGJJyzLWMXsAWeSBBEGnoXwqgSlnQ7so48XraoeKCq40wTzQW+BKng6zcygiabrs8DyxF7rs3DclY1lUAm2nHByw7MtIuykX2ZR8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787753316; c=relaxed/simple; bh=CFG87ZaWpvxar+LmzhhuZpRsOTZ64BqB1+w3gYa98yc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dEez06kcpbeBBHPJevrTQLDMOZsdJIXLLwxyTUvgMe8Y/R8+yRNV9/B27YN5p5ZoEUYmBNtv/l0NCVaDYPT7NQObLtA8kyT/DdfvTat3vqbnitGhcSey7H6mcbBbYcagSXMWIt95kBseU0L+kRLkoc82C446IqpZXGuS0EPuGSQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dZiGcDnl; 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="dZiGcDnl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1AD271F000E9; Wed, 26 Aug 2026 14:08:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787753314; bh=58CqlTkVH+yeGKqVx3x8yllINuupuUvSuHy1ToSmt8o=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=dZiGcDnlz6tDjWuQcAuRDVN9X4hvLFz0grc8asWYHCXwDkmEDtD1eQHI4owQslV/P yAaCW+FUfOddDcMs/zBZLDSCSsiD58j+7hEzQq9N5QgR7UZaMIXrMACPfPQvo+KSh0 vyXP/eHeK8girFF8S3HcvBQr+HSkPUwgDlm32kwCdF2+VvK9A7LnhNOKrz/MCMUxMp NHwdwHV48AZsjvxm2wtYBzBHan8CLH3hZyCPURljSi6QqAtVL6xm7B5gle5a3s5mQk xgyEdcZMZf1X1CfJnFSIN3EXL/dLtc2Z1nfxGuBeB1+eJhXwweci6L8dADVW2B/2xS ZhmUoi1HsZ6jg== Date: Wed, 26 Aug 2026 17:08:31 +0300 From: Leon Romanovsky To: Alison Schofield Cc: "Rafael J. Wysocki" , Len Brown , Saket Dumbre , Bjorn Helgaas , Logan Gunthorpe , linux-acpi@vger.kernel.org, acpica-devel@lists.linux.dev, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Lukas Wunner , "Natu, Mahesh" Subject: Re: [PATCH RFC 0/7] PCI/HMAT: Describe P2PDMA reachability and performance Message-ID: <20260826140831.GF42790@unreal> References: <20260812-hmat-p2p-v1-0-75ac41380585@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@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 Mon, Aug 24, 2026 at 01:15:34PM -0700, Alison Schofield wrote: > On Wed, Aug 12, 2026 at 10:47:37PM +0300, Leon Romanovsky wrote: > > Linux derives P2PDMA reachability from visible PCI topology, ACS > > configuration, and a host-bridge whitelist. It cannot describe conditional > > or slower cross-host-bridge paths; passthrough can hide the physical peer > > relationships. > > > > This RFC series implements the proposed ACPI HMAT Type 3 extension below. > > Hi Leon, > > Is there an ECN document for review alongside this? > I get that the table below is a snapshot of the expected change, but > would appreciate the long version to read. Sure, Mahesh sent me the document, which I promised to convert to the mailing list format. I will send the official RFC to the linux-acpi ML slightly later. Thanks > > Please add linux-cxl to CC list on future postings. > > -- Alison > > > > Directional Generic Port matrices describe reachability, ordering, latency, > > and bandwidth. Linux uses ordered paths to authorize P2PDMA and their > > latency/bandwidth to rank providers. A VMM could translate these matrices > > into guest domains; that is outside this series. > > > > HMAT Type 3 structure > > > > Field Offset Bytes Meaning > > --------------------------------------------------------------- > > Type: 0 2 value 3 > > Length: 4 4 entire structure > > Flags: 8 1 traffic classes > > Data-type: 9 1 metric selector > > Initiators: 12 4 Generic Port count (s) > > Targets: 16 4 Generic Port count (t) > > Base-unit: 24 8 ps or MB/s; non-zero > > Initiator-PDs: 32 4*s proximity-domain list > > Target-PDs: 32+4*s 4*t proximity-domain list > > Matrix: 32+4*(s+t) 2*s*t directional Entry[i][j] > > Reserved: bytes 2-3, 10-11, and 20-23 > > > > Flags: encoding > > bit 0 non-UIO > > bit 1 UIO > > > > Metrics: selector > > 0/1/2 access/read/write latency > > 3/4/5 access/read/write bandwidth > > > > Direction: Initiator PD[i] -- Entry[i][j] metric --> Target PD[j] > > > > ---------------------------------------------------------------------- > > Based on [PATCH v3 00/17] PCI/P2PDMA: Fix ACS egress control handling > > https://lore.kernel.org/all/20260811-fix-p2p-acs-v3-0-efc488ee7c03@nvidia.com/ > > > > Signed-off-by: Leon Romanovsky > > --- > > Leon Romanovsky (7): > > ACPICA: Define PCIe P2P latency and bandwidth information > > ACPI: HMAT: Make PCIe P2P paths available to consumers > > PCI/P2PDMA: Authorize HMAT-described cross-host-bridge P2P > > PCI/P2PDMA: Prefer providers with better HMAT performance > > ACPI: HMAT: Add KUnit tests for PCIe P2P matrix semantics > > PCI/P2PDMA: Add KUnit tests for HMAT policy boundaries > > PCI/P2PDMA: Add KUnit tests for HMAT provider ranking > > > > drivers/acpi/numa/Kconfig | 13 ++ > > drivers/acpi/numa/Makefile | 1 + > > drivers/acpi/numa/hmat.c | 245 +++++++++++++++++++++- > > drivers/acpi/numa/hmat_test.c | 223 ++++++++++++++++++++ > > drivers/acpi/numa/hmat_test.h | 17 ++ > > drivers/pci/Kconfig | 14 ++ > > drivers/pci/Makefile | 1 + > > drivers/pci/p2pdma.c | 300 ++++++++++++++++++++------ > > drivers/pci/p2pdma_test.c | 477 ++++++++++++++++++++++++++++++++++++++++++ > > drivers/pci/pci.h | 23 ++ > > include/acpi/actbl1.h | 27 ++- > > include/linux/acpi.h | 26 +++ > > 12 files changed, 1298 insertions(+), 69 deletions(-) > > --- > > base-commit: bc5261fca94dd94ab557cc0852ce465d9c3ab8b0 > > change-id: 20260715-hmat-p2p-eb4971a9d731 > > > > Best regards, > > -- > > Leon Romanovsky > > >