linux-kernel - [PATCH 3.16 086/305] x86/PCI: Mark Broadwell-EP Home Agent 1 as having non-compliant BARs

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Message-ID: <lsq.1471110171.899968598@decadent.org.uk>
Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Bjorn Helgaas" <bhelgaas@...gle.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Prarit Bhargava" <prarit@...hat.com>,
	"Ingo Molnar" <mingo@...hat.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Andi Kleen" <ak@...ux.intel.com>
Subject: [PATCH 3.16 086/305] x86/PCI: Mark Broadwell-EP Home Agent 1 as
 having non-compliant BARs

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Prarit Bhargava <prarit@...hat.com>

commit da77b67195de1c65bef4908fa29967c4d0af2da2 upstream.

Commit b894157145e4 ("x86/PCI: Mark Broadwell-EP Home Agent & PCU as having
non-compliant BARs") marked Home Agent 0 & PCU has having non-compliant
BARs.  Home Agent 1 also has non-compliant BARs.

Mark Home Agent 1 as having non-compliant BARs so the PCI core doesn't
touch them.

The problem with these devices is documented in the Xeon v4 specification
update:

  BDF2          PCI BARs in the Home Agent Will Return Non-Zero Values
                During Enumeration

  Problem:      During system initialization the Operating System may access
                the standard PCI BARs (Base Address Registers).  Due to
                this erratum, accesses to the Home Agent BAR registers (Bus
                1; Device 18; Function 0,4; Offsets (0x14-0x24) will return
                non-zero values.

  Implication:  The operating system may issue a warning.  Intel has not
                observed any functional failures due to this erratum.

Link: http://www.intel.com/content/www/us/en/processors/xeon/xeon-e5-v4-spec-update.html
Fixes: b894157145e4 ("x86/PCI: Mark Broadwell-EP Home Agent & PCU as having non-compliant BARs")
Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Ingo Molnar <mingo@...hat.com>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/pci/fixup.c | 7 +++++++
 1 file changed, 7 insertions(+)

--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -554,9 +554,16 @@ static void twinhead_reserve_killing_zon
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x27B9, twinhead_reserve_killing_zone);
 
+/*
+ * Broadwell EP Home Agent BARs erroneously return non-zero values when read.
+ *
+ * See http://www.intel.com/content/www/us/en/processors/xeon/xeon-e5-v4-spec-update.html
+ * entry BDF2.
+ */
 static void pci_bdwep_bar(struct pci_dev *dev)
 {
 	dev->non_compliant_bars = 1;
 }
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x6f60, pci_bdwep_bar);
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x6fa0, pci_bdwep_bar);
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x6fc0, pci_bdwep_bar);