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(-)
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.
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 <leonro@nvidia.com>
---
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 <leonro@nvidia.com>
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. 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 <leonro@nvidia.com> > --- > 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 <leonro@nvidia.com> >
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 <leonro@nvidia.com> > > --- > > 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 <leonro@nvidia.com> > > >
attached Thank you, Mahesh ________________________________ From: Schofield, Alison <alison.schofield@intel.com> Sent: Monday, August 24, 2026 1:15 PM To: Leon Romanovsky <leon@kernel.org> Cc: Rafael J. Wysocki <rafael@kernel.org>; Len Brown <lenb@kernel.org>; Saket Dumbre <saket.dumbre@intel.com>; Bjorn Helgaas <bhelgaas@google.com>; Logan Gunthorpe <logang@deltatee.com>; linux-acpi@vger.kernel.org <linux-acpi@vger.kernel.org>; acpica-devel@lists.linux.dev <acpica-devel@lists.linux.dev>; linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; linux-pci@vger.kernel.org <linux-pci@vger.kernel.org>; Lukas Wunner <lukas@wunner.de>; Natu, Mahesh <mahesh.natu@intel.com> Subject: Re: [PATCH RFC 0/7] PCI/HMAT: Describe P2PDMA reachability and performance 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. 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 <leonro@nvidia.com> > --- > 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 <leonro@nvidia.com> >
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