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Date: Thu, 13 Aug 2026 14:01:53 +0300
From: Leon Romanovsky <leon@kernel.org>
To: "Rafael J. Wysocki (Intel)" <rafael@kernel.org>
Cc: 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,
	acpica-devel@lists.linux.dev, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, Lukas Wunner <lukas@wunner.de>,
	"Natu, Mahesh" <mahesh.natu@intel.com>
Subject: Re: [PATCH RFC 1/7] ACPICA: Define PCIe P2P latency and bandwidth
 information
Message-ID: <20260813110153.GB79153@unreal>
References: <20260812-hmat-p2p-v1-0-75ac41380585@nvidia.com>
 <20260812-hmat-p2p-v1-1-75ac41380585@nvidia.com>
 <CAJZ5v0iDR1LN=6QosMvNbctHKqEmzG0Jg6eS1np5MQkfLjXzAA@mail.gmail.com>
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On Thu, Aug 13, 2026 at 12:13:39PM +0200, Rafael J. Wysocki (Intel) wrote:
> On Wed, Aug 12, 2026 at 9:48 PM Leon Romanovsky <leon@kernel.org> wrote:
> >
> > From: Leon Romanovsky <leonro@nvidia.com>
> >
> > PCIe topology alone cannot tell an operating system whether traffic may
> > cross host bridges, what ordering rules it needs, or how expensive the path
> > is. Encoding this knowledge in chipset lists duplicates platform policy and
> > cannot survive a virtualized topology.
> >
> > Define HMAT Type 3 as a firmware contract for directional Generic Port P2P
> > paths, including separate ordered and Unordered I/O applicability. This
> > gives platform software a standard way to distinguish unsupported,
> > conditional, and usable paths. The definition follows a proposed ACPI ECN.
> >
> > Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> > ---
> >  include/acpi/actbl1.h | 27 ++++++++++++++++++++++++++-
> >  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> As per Documentation/driver-api/acpi/linuxized-acpica.rst, please
> submit a pull request with this change to the upstream ACPICA project
> on GitHub.  The Linux patch will become applicable when there is a
> corresponding commit upstream.

Sure, we will. However, at this stage, we are looking for
feedback on the idea.

Thanks.