linux-kernel - [RFC PATCH v4 33/38] Documentation: PCI: endpoint: pci-epf-vntb: Update and add mwN

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260118135440.1958279-34-den@valinux.co.jp>
Date: Sun, 18 Jan 2026 22:54:35 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank.Li@....com,
	dave.jiang@...el.com,
	cassel@...nel.org,
	mani@...nel.org,
	kwilczynski@...nel.org,
	kishon@...nel.org,
	bhelgaas@...gle.com,
	geert+renesas@...der.be,
	robh@...nel.org,
	vkoul@...nel.org,
	jdmason@...zu.us,
	allenbh@...il.com,
	jingoohan1@...il.com,
	lpieralisi@...nel.org
Cc: linux-pci@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	devicetree@...r.kernel.org,
	dmaengine@...r.kernel.org,
	iommu@...ts.linux.dev,
	ntb@...ts.linux.dev,
	netdev@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	arnd@...db.de,
	gregkh@...uxfoundation.org,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	magnus.damm@...il.com,
	krzk+dt@...nel.org,
	conor+dt@...nel.org,
	corbet@....net,
	skhan@...uxfoundation.org,
	andriy.shevchenko@...ux.intel.com,
	jbrunet@...libre.com,
	utkarsh02t@...il.com
Subject: [RFC PATCH v4 33/38] Documentation: PCI: endpoint: pci-epf-vntb: Update and add mwN_offset usage

Add a concrete example showing how to pack multiple memory windows into
a single BAR by using 'mwN_bar' and 'mwN_offset'.

Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
 Documentation/PCI/endpoint/pci-vntb-howto.rst | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/Documentation/PCI/endpoint/pci-vntb-howto.rst b/Documentation/PCI/endpoint/pci-vntb-howto.rst
index 3679f5c30254..097826f946a9 100644
--- a/Documentation/PCI/endpoint/pci-vntb-howto.rst
+++ b/Documentation/PCI/endpoint/pci-vntb-howto.rst
@@ -90,9 +90,9 @@ of the function device and is populated with the following NTB specific
 attributes that can be configured by the user::
 
 	# ls functions/pci_epf_vntb/func1/pci_epf_vntb.0/
-	ctrl_bar  db_count  mw1_bar  mw2_bar  mw3_bar  mw4_bar	spad_count
-	db_bar	  mw1	    mw2      mw3      mw4      num_mws	vbus_number
-	vntb_vid  vntb_pid
+	ctrl_bar  mw1         mw2         mw3         mw4         num_mws      vntb_pid
+	db_bar    mw1_bar     mw2_bar     mw3_bar     mw4_bar     spad_count   vntb_vid
+	db_count  mw1_offset  mw2_offset  mw3_offset  mw4_offset  vbus_number
 
 A sample configuration for NTB function is given below::
 
@@ -111,6 +111,19 @@ A sample configuration for virtual NTB driver for virtual PCI bus::
 	# echo 0x080A > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_pid
 	# echo 0x10 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vbus_number
 
+When BAR resources are tight but you still need to create many memory
+windows, you can pack multiple windows into a single BAR by setting
+``mwN_bar`` to the same BAR number and using ``mwN_offset`` to place each
+MW within that BAR. Offsets are in bytes and the resulting regions must not
+overlap and must exactly fit within the BAR size. This may fail depending
+on the underlying EPC capabilities::
+
+	# echo 0xE0000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1
+	# echo 0x20000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw2
+	# echo 0xE0000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw2_offset
+	# echo 2 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1_bar
+	# echo 2 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw2_bar
+
 Binding pci-epf-vntb Device to EP Controller
 --------------------------------------------
 
-- 
2.51.0