[v2] PCI/AER: Do not clear AER bits if we don't own AER

Commit Message

Alex G. July 23, 2018, 8:01 p.m. UTC

When we don't own AER, we shouldn't touch the AER error bits. Clearing
error bits willy-nilly might cause firmware to miss some errors. In
theory, these bits get cleared by FFS, or via ACPI _HPX method. These
mechanisms are not subject to the problem.

This race is mostly of theoretical significance, since I can't
reasonably demonstrate this race in the lab.

On a side-note, pcie_aer_is_kernel_first() is created to alleviate the
need for two checks: aer_cap and get_firmware_first().

Signed-off-by: Alexandru Gagniuc <[e-mail]>
---
 drivers/pci/pcie/aer.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

Comments

kernel test robot July 25, 2018, 1:24 a.m. UTC | #1

Hi Alexandru,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on pci/next]
[also build test WARNING on v4.18-rc6 next-20180724]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Alexandru-Gagniuc/PCI-AER-Do-not-clear-AER-bits-if-we-don-t-own-AER/20180725-003708
base:   https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git next
config: x86_64-randconfig-s0-07250049 (attached as .config)
compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/string.h:6:0,
                    from include/linux/uuid.h:20,
                    from include/linux/cper.h:24,
                    from drivers/pci/pcie/aer.c:15:
   drivers/pci/pcie/aer.c: In function 'pci_enable_pcie_error_reporting':
   drivers/pci/pcie/aer.c:371:7: error: implicit declaration of function 'pcie_aer_is_kernel_first' [-Werror=implicit-function-declaration]
     if (!pcie_aer_is_kernel_first(dev))
          ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> drivers/pci/pcie/aer.c:371:2: note: in expansion of macro 'if'
     if (!pcie_aer_is_kernel_first(dev))
     ^~
   cc1: some warnings being treated as errors

vim +/if +371 drivers/pci/pcie/aer.c

   365	
   366	#define	PCI_EXP_AER_FLAGS	(PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \
   367					 PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
   368	
   369	int pci_enable_pcie_error_reporting(struct pci_dev *dev)
   370	{
 > 371		if (!pcie_aer_is_kernel_first(dev))
   372			return -EIO;
   373	
   374		return pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_AER_FLAGS);
   375	}
   376	EXPORT_SYMBOL_GPL(pci_enable_pcie_error_reporting);
   377	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Patch

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index a2e88386af28..85c3e173c025 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -307,6 +307,12 @@  int pcie_aer_get_firmware_first(struct pci_dev *dev)
 		aer_set_firmware_first(dev);
 	return dev->__aer_firmware_first;
 }
+
+static bool pcie_aer_is_kernel_first(struct pci_dev *dev)
+{
+	return !!dev->aer_cap && !pcie_aer_get_firmware_first(dev);
+}
+
 #define	PCI_EXP_AER_FLAGS	(PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \
 				 PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
 
@@ -337,10 +343,7 @@  bool aer_acpi_firmware_first(void)
 
 int pci_enable_pcie_error_reporting(struct pci_dev *dev)
 {
-	if (pcie_aer_get_firmware_first(dev))
-		return -EIO;
-
-	if (!dev->aer_cap)
+	if (!pcie_aer_is_kernel_first(dev))
 		return -EIO;
 
 	return pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_AER_FLAGS);
@@ -349,7 +352,7 @@  EXPORT_SYMBOL_GPL(pci_enable_pcie_error_reporting);
 
 int pci_disable_pcie_error_reporting(struct pci_dev *dev)
 {
-	if (pcie_aer_get_firmware_first(dev))
+	if (!pcie_aer_is_kernel_first(dev))
 		return -EIO;
 
 	return pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
@@ -383,10 +386,10 @@  int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
 	if (!pci_is_pcie(dev))
 		return -ENODEV;
 
-	pos = dev->aer_cap;
-	if (!pos)
+	if (pcie_aer_is_kernel_first(dev))
 		return -EIO;
 
+	pos = dev->aer_cap;
 	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);