Merge branch 'pci/interrupts'

  - Extend boot interrupt quirk to cover several Xeon chipsets (Sean V
    Kelley)

  - Add documentation about boot interrupts (Sean V Kelley)

* pci/interrupts:
  Documentation: PCI: Add background on Boot Interrupts
  PCI: Add boot interrupt quirk mechanism for Xeon chipsets

Documentation/PCI/boot-interrupts.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Boot Interrupts
+===============
+
+:Author: - Sean V Kelley <sean.v.kelley@linux.intel.com>
+
+Overview
+========
+
+On PCI Express, interrupts are represented with either MSI or inbound
+interrupt messages (Assert_INTx/Deassert_INTx). The integrated IO-APIC in a
+given Core IO converts the legacy interrupt messages from PCI Express to
+MSI interrupts.  If the IO-APIC is disabled (via the mask bits in the
+IO-APIC table entries), the messages are routed to the legacy PCH. This
+in-band interrupt mechanism was traditionally necessary for systems that
+did not support the IO-APIC and for boot. Intel in the past has used the
+term "boot interrupts" to describe this mechanism. Further, the PCI Express
+protocol describes this in-band legacy wire-interrupt INTx mechanism for
+I/O devices to signal PCI-style level interrupts. The subsequent paragraphs
+describe problems with the Core IO handling of INTx message routing to the
+PCH and mitigation within BIOS and the OS.
+
+
+Issue
+=====
+
+When in-band legacy INTx messages are forwarded to the PCH, they in turn
+trigger a new interrupt for which the OS likely lacks a handler. When an
+interrupt goes unhandled over time, they are tracked by the Linux kernel as
+Spurious Interrupts. The IRQ will be disabled by the Linux kernel after it
+reaches a specific count with the error "nobody cared". This disabled IRQ
+now prevents valid usage by an existing interrupt which may happen to share
+the IRQ line.
+
+  irq 19: nobody cared (try booting with the "irqpoll" option)
+  CPU: 0 PID: 2988 Comm: irq/34-nipalk Tainted: 4.14.87-rt49-02410-g4a640ec-dirty #1
+  Hardware name: National Instruments NI PXIe-8880/NI PXIe-8880, BIOS 2.1.5f1 01/09/2020
+  Call Trace:
+  <IRQ>
+   ? dump_stack+0x46/0x5e
+   ? __report_bad_irq+0x2e/0xb0
+   ? note_interrupt+0x242/0x290
+   ? nNIKAL100_memoryRead16+0x8/0x10 [nikal]
+   ? handle_irq_event_percpu+0x55/0x70
+   ? handle_irq_event+0x4f/0x80
+   ? handle_fasteoi_irq+0x81/0x180
+   ? handle_irq+0x1c/0x30
+   ? do_IRQ+0x41/0xd0
+   ? common_interrupt+0x84/0x84
+  </IRQ>
+
+  handlers:
+  irq_default_primary_handler threaded usb_hcd_irq
+  Disabling IRQ #19
+
+
+Conditions
+==========
+
+The use of threaded interrupts is the most likely condition to trigger
+this problem today. Threaded interrupts may not be reenabled after the IRQ
+handler wakes. These "one shot" conditions mean that the threaded interrupt
+needs to keep the interrupt line masked until the threaded handler has run.
+Especially when dealing with high data rate interrupts, the thread needs to
+run to completion; otherwise some handlers will end up in stack overflows
+since the interrupt of the issuing device is still active.
+
+Affected Chipsets
+=================
+
+The legacy interrupt forwarding mechanism exists today in a number of
+devices including but not limited to chipsets from AMD/ATI, Broadcom, and
+Intel. Changes made through the mitigations below have been applied to
+drivers/pci/quirks.c
+
+Starting with ICX there are no longer any IO-APICs in the Core IO's
+devices.  IO-APIC is only in the PCH.  Devices connected to the Core IO's
+PCIe Root Ports will use native MSI/MSI-X mechanisms.
+
+Mitigations
+===========
+
+The mitigations take the form of PCI quirks. The preference has been to
+first identify and make use of a means to disable the routing to the PCH.
+In such a case a quirk to disable boot interrupt generation can be
+added.[1]
+
+  Intel® 6300ESB I/O Controller Hub
+  Alternate Base Address Register:
+   BIE: Boot Interrupt Enable
+	  0 = Boot interrupt is enabled.
+	  1 = Boot interrupt is disabled.
+
+  Intel® Sandy Bridge through Sky Lake based Xeon servers:
+  Coherent Interface Protocol Interrupt Control
+   dis_intx_route2pch/dis_intx_route2ich/dis_intx_route2dmi2:
+	  When this bit is set. Local INTx messages received from the
+	  Intel® Quick Data DMA/PCI Express ports are not routed to legacy
+	  PCH - they are either converted into MSI via the integrated IO-APIC
+	  (if the IO-APIC mask bit is clear in the appropriate entries)
+	  or cause no further action (when mask bit is set)
+
+In the absence of a way to directly disable the routing, another approach
+has been to make use of PCI Interrupt pin to INTx routing tables for
+purposes of redirecting the interrupt handler to the rerouted interrupt
+line by default.  Therefore, on chipsets where this INTx routing cannot be
+disabled, the Linux kernel will reroute the valid interrupt to its legacy
+interrupt. This redirection of the handler will prevent the occurrence of
+the spurious interrupt detection which would ordinarily disable the IRQ
+line due to excessive unhandled counts.[2]
+
+The config option X86_REROUTE_FOR_BROKEN_BOOT_IRQS exists to enable (or
+disable) the redirection of the interrupt handler to the PCH interrupt
+line. The option can be overridden by either pci=ioapicreroute or
+pci=noioapicreroute.[3]
+
+
+More Documentation
+==================
+
+There is an overview of the legacy interrupt handling in several datasheets
+(6300ESB and 6700PXH below). While largely the same, it provides insight
+into the evolution of its handling with chipsets.
+
+Example of disabling of the boot interrupt
+------------------------------------------
+
+Intel® 6300ESB I/O Controller Hub (Document # 300641-004US)
+	5.7.3 Boot Interrupt
+	https://www.intel.com/content/dam/doc/datasheet/6300esb-io-controller-hub-datasheet.pdf
+
+Intel® Xeon® Processor E5-1600/2400/2600/4600 v3 Product Families
+Datasheet - Volume 2: Registers (Document # 330784-003)
+	6.6.41 cipintrc Coherent Interface Protocol Interrupt Control
+	https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/xeon-e5-v3-datasheet-vol-2.pdf
+
+Example of handler rerouting
+----------------------------
+
+Intel® 6700PXH 64-bit PCI Hub (Document # 302628)
+	2.15.2 PCI Express Legacy INTx Support and Boot Interrupt
+	https://www.intel.com/content/dam/doc/datasheet/6700pxh-64-bit-pci-hub-datasheet.pdf
+
+
+If you have any legacy PCI interrupt questions that aren't answered, email me.
+
+Cheers,
+    Sean V Kelley
+    sean.v.kelley@linux.intel.com
+
+[1] https://lore.kernel.org/r/12131949181903-git-send-email-sassmann@suse.de/
+[2] https://lore.kernel.org/r/12131949182094-git-send-email-sassmann@suse.de/
+[3] https://lore.kernel.org/r/487C8EA7.6020205@suse.de/

Documentation/PCI/index.rst

@@ -16,3 +16,4 @@ Linux PCI Bus Subsystem
    pci-error-recovery
    pcieaer-howto
    endpoint/index
+   boot-interrupts

drivers/pci/quirks.c

@@ -1970,26 +1970,92 @@ DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_80332_1,	quirk
 /*
  * IO-APIC1 on 6300ESB generates boot interrupts, see Intel order no
  * 300641-004US, section 5.7.3.
+ *
+ * Core IO on Xeon E5 1600/2600/4600, see Intel order no 326509-003.
+ * Core IO on Xeon E5 v2, see Intel order no 329188-003.
+ * Core IO on Xeon E7 v2, see Intel order no 329595-002.
+ * Core IO on Xeon E5 v3, see Intel order no 330784-003.
+ * Core IO on Xeon E7 v3, see Intel order no 332315-001US.
+ * Core IO on Xeon E5 v4, see Intel order no 333810-002US.
+ * Core IO on Xeon E7 v4, see Intel order no 332315-001US.
+ * Core IO on Xeon D-1500, see Intel order no 332051-001.
+ * Core IO on Xeon Scalable, see Intel order no 610950.
  */
-#define INTEL_6300_IOAPIC_ABAR		0x40
+#define INTEL_6300_IOAPIC_ABAR		0x40	/* Bus 0, Dev 29, Func 5 */
 #define INTEL_6300_DISABLE_BOOT_IRQ	(1<<14)
 
+#define INTEL_CIPINTRC_CFG_OFFSET	0x14C	/* Bus 0, Dev 5, Func 0 */
+#define INTEL_CIPINTRC_DIS_INTX_ICH	(1<<25)
+
 static void quirk_disable_intel_boot_interrupt(struct pci_dev *dev)
 {
 	u16 pci_config_word;
+	u32 pci_config_dword;
 
 	if (noioapicquirk)
 		return;
 
-	pci_read_config_word(dev, INTEL_6300_IOAPIC_ABAR, &pci_config_word);
-	pci_config_word |= INTEL_6300_DISABLE_BOOT_IRQ;
-	pci_write_config_word(dev, INTEL_6300_IOAPIC_ABAR, pci_config_word);
-
+	switch (dev->device) {
+	case PCI_DEVICE_ID_INTEL_ESB_10:
+		pci_read_config_word(dev, INTEL_6300_IOAPIC_ABAR,
+				     &pci_config_word);
+		pci_config_word |= INTEL_6300_DISABLE_BOOT_IRQ;
+		pci_write_config_word(dev, INTEL_6300_IOAPIC_ABAR,
+				      pci_config_word);
+		break;
+	case 0x3c28:	/* Xeon E5 1600/2600/4600	*/
+	case 0x0e28:	/* Xeon E5/E7 V2		*/
+	case 0x2f28:	/* Xeon E5/E7 V3,V4		*/
+	case 0x6f28:	/* Xeon D-1500			*/
+	case 0x2034:	/* Xeon Scalable Family		*/
+		pci_read_config_dword(dev, INTEL_CIPINTRC_CFG_OFFSET,
+				      &pci_config_dword);
+		pci_config_dword |= INTEL_CIPINTRC_DIS_INTX_ICH;
+		pci_write_config_dword(dev, INTEL_CIPINTRC_CFG_OFFSET,
+				       pci_config_dword);
+		break;
+	default:
+		return;
+	}
 	pci_info(dev, "disabled boot interrupts on device [%04x:%04x]\n",
 		 dev->vendor, dev->device);
 }
-DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,   PCI_DEVICE_ID_INTEL_ESB_10,	quirk_disable_intel_boot_interrupt);
-DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,   PCI_DEVICE_ID_INTEL_ESB_10,	quirk_disable_intel_boot_interrupt);
+/*
+ * Device 29 Func 5 Device IDs of IO-APIC
+ * containing ABAR—APIC1 Alternate Base Address Register
+ */
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_ESB_10,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_ESB_10,
+		quirk_disable_intel_boot_interrupt);
+
+/*
+ * Device 5 Func 0 Device IDs of Core IO modules/hubs
+ * containing Coherent Interface Protocol Interrupt Control
+ *
+ * Device IDs obtained from volume 2 datasheets of commented
+ * families above.
+ */
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	0x3c28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	0x0e28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	0x2f28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	0x6f28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	0x2034,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	0x3c28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	0x0e28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	0x2f28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	0x6f28,
+		quirk_disable_intel_boot_interrupt);
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL,	0x2034,
+		quirk_disable_intel_boot_interrupt);
 
 /* Disable boot interrupts on HT-1000 */
 #define BC_HT1000_FEATURE_REG		0x64