linux-kernel - [PATCH v2 0/2] PCI: Fix the wrong reading of register fields

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Message-Id: <20250115134154.9220-1-sjiwei@163.com>
Date: Wed, 15 Jan 2025 21:41:52 +0800
From: Jiwei Sun <sjiwei@....com>
To: macro@...am.me.uk,
	ilpo.jarvinen@...ux.intel.com,
	bhelgaas@...gle.com
Cc: linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	helgaas@...nel.org,
	lukas@...ner.de,
	ahuang12@...ovo.com,
	sunjw10@...ovo.com,
	jiwei.sun.bj@...com,
	sunjw10@...look.com
Subject: [PATCH v2 0/2] PCI: Fix the wrong reading of register fields

From: Jiwei Sun <sunjw10@...ovo.com>

Since commit de9a6c8d5dbf ("PCI/bwctrl: Add pcie_set_target_speed() to set
PCIe Link Speed"), there are two potential issues in the function
pcie_failed_link_retrain().

(1) The macro PCIE_LNKCTL2_TLS2SPEED() and PCIE_LNKCAP_SLS2SPEED() just
uses the link speed field of the registers. However, there are many other
different function fields in the Link Control 2 Register or the Link
Capabilities Register. If the register value is directly used by the two
macros, it may cause getting an error link speed value (PCI_SPEED_UNKNOWN).

(2) In the pcie_failed_link_retrain(), the local variable lnkctl2 is not
changed after reading from PCI_EXP_LNKCTL2. It might cause that the
removing 2.5GT/s downstream link speed restriction codes are not executed.

In order to avoid the above-mentioned potential issues, only keep link
speed field of the two registers before using and reread the Link Control 2
Register before using.

This series focuses on the first patch of the original series [1]. The
second one of the original series will submitted via the other single
patch.

Fixes: de9a6c8d5dbf ("PCI/bwctrl: Add pcie_set_target_speed() to set PCIe Link Speed")

[1] https://lore.kernel.org/linux-pci/tencent_DD9CBE5B44210B43A04EF8DAF52506A08509@qq.com/
---
v2 changes:
 https://lore.kernel.org/linux-pci/tencent_753C9F9DFEC140A750F2778E6879E1049406@qq.com/
 - divide the two issues into different patches
 - get fixed inside the macros
---

Jiwei Sun (2):
  PCI: Fix the wrong reading of register fields
  PCI: reread the Link Control 2 Register before using

 drivers/pci/pci.h    | 30 +++++++++++++++++-------------
 drivers/pci/quirks.c |  1 +
 2 files changed, 18 insertions(+), 13 deletions(-)

-- 
2.34.1