linux-kernel - [RFC PATCH v2 0/1] VFIO ioctl for TLP Processing Hints

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Message-ID: <20250602230641.821485-1-wathsala.vithanage@arm.com>
Date: Mon,  2 Jun 2025 23:06:39 +0000
From: Wathsala Vithanage <wathsala.vithanage@....com>
To: linux-kernel@...r.kernel.org
Cc: alex.williamson@...hat.com,
	gg@...pe.ca,
	kevin.tian@...el.com,
	bhelgaas@...gle.com,
	pstanner@...hat.com,
	linux@...blig.org,
	schnelle@...ux.ibm.com,
	Yunxiang.Li@....com,
	kvm@...r.kernel.org,
	Wathsala Vithanage <wathsala.vithanage@....com>
Subject: [RFC PATCH v2 0/1] VFIO ioctl for TLP Processing Hints

Linux v6.13 introduced the PCIe TLP Processing Hints (TPH) feature for
direct cache injection. As described in the relevant patch set [1],
direct cache injection in supported hardware allows optimal platform
resource utilization for specific requests on the PCIe bus. This feature
is currently available only for kernel device drivers. However, user
space applications, especially those whose performance is sensitive to
the latency of inbound writes as seen by a CPU core, may benefit from
using this information (E.g., DPDK cache stashing RFC [2] or an HPC
application running in a VM). For such applications to enable and
configure TPH on PCIe devices, this RFC proposes a new VFIO ioctl.

[1] lore.kernel.org/linux-pci/20241002165954.128085-1-wei.huang2@....com
[2] inbox.dpdk.org/dev/20241021015246.304431-2-wathsala.vithanage@....com

V1->V2:
 * Rewrite as a VFIO IOCTL
 * Add missing padding for structs
 * Increase maximum steering tags per IOCTL to 2048

Wathsala Vithanage (1):
  vfio/pci: add PCIe TPH device ioctl

 drivers/vfio/pci/vfio_pci_core.c | 153 +++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h        |  83 +++++++++++++++++
 2 files changed, 236 insertions(+)

-- 
2.43.0