linux-kernel - Re: 4.6-rc*: Kernel unaligned access at pci_bus_read_config

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Message-Id: <20160618.234908.1671877676732375612.davem@davemloft.net>
Date:	Sat, 18 Jun 2016 23:49:08 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	matorola@...il.com
Cc:	mroos@...ux.ee, sparclinux@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: 4.6-rc*: Kernel unaligned access at
 pci_bus_read_config_dword+0x64/0x80

From: David Miller <davem@...emloft.net>
Date: Sat, 18 Jun 2016 21:04:21 -0700 (PDT)

> From: Anatoly Pugachev <matorola@...il.com>
> Date: Thu, 16 Jun 2016 13:02:07 +0300
> 
>> bisected to git commit 63e3027
> 
> That's a merge commit that adds 100 different commits, and this happened
> way back in March.
> 
> Please find the exact dword access in:
> 
> 	drivers/pci/pcie/portdrv_{core,pci,bus}.c
> 
> that triggers this unaligned access so we can debug this further.

Meanwhile I figured it out, this should fix the bug:

diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c
index dfbab61..1fa3a32 100644
--- a/drivers/pci/vc.c
+++ b/drivers/pci/vc.c
@@ -221,9 +221,9 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
 		else
 			pci_write_config_word(dev, pos + PCI_VC_PORT_CTRL,
 					      *(u16 *)buf);
-		buf += 2;
+		buf += 4;
 	}
-	len += 2;
+	len += 4;
 
 	/*
 	 * If we have any Low Priority VCs and a VC Arbitration Table Offset