From 45687f96c112adda2f1d1f05b977661eb00d5a1c Mon Sep 17 00:00:00 2001
From: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Date: Tue, 17 Jul 2018 10:31:23 -0500
Subject: [PATCH] PCI/AER: Don't clear AER bits if error handling is Firmware-First
Git-commit: 45687f96c112adda2f1d1f05b977661eb00d5a1c
Patch-mainline: v4.19-rc1
References: bsc#1161561

If the platform requests Firmware-First error handling, firmware is
responsible for reading and clearing AER status bits.  If OSPM also clears
them, we may miss errors.  See ACPI v6.2, sec 18.3.2.5 and 18.4.

This race is mostly of theoretical significance, as it is not easy to
reasonably demonstrate it in testing.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
[bhelgaas: add similar guards to pci_cleanup_aer_uncorrect_error_status()
and pci_aer_clear_fatal_status()]

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/pci/pcie/aer/aerdrv_core.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -70,6 +70,9 @@ int pci_cleanup_aer_uncorrect_error_stat
 	if (!pos)
 		return -EIO;
 
+	if (pcie_aer_get_firmware_first(dev))
+		return -EIO;
+
 	/* Clear status bits for ERR_NONFATAL errors only */
 	pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, &status);
 	pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_SEVER, &sev);
@@ -90,6 +93,9 @@ void pci_aer_clear_fatal_status(struct p
 	if (!pos)
 		return;
 
+	if (pcie_aer_get_firmware_first(dev))
+		return;
+
 	/* Clear status bits for ERR_FATAL errors only */
 	pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, &status);
 	pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_SEVER, &sev);
@@ -111,6 +117,9 @@ int pci_cleanup_aer_error_status_regs(st
 	if (!pos)
 		return -EIO;
 
+	if (pcie_aer_get_firmware_first(dev))
+		return -EIO;
+
 	port_type = pci_pcie_type(dev);
 	if (port_type == PCI_EXP_TYPE_ROOT_PORT) {
 		pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &status);