PCI: Disable Bus Master only on kexec reboot

Add a flag to tell the PCI subsystem that kernel is shutting down in
preparation to kexec a kernel.  Add code in PCI subsystem to use this flag
to clear Bus Master bit on PCI devices only in case of kexec reboot.

This fixes a power-off problem on Acer Aspire V5-573G and likely other
machines and avoids any other issues caused by clearing Bus Master bit on
PCI devices in normal shutdown path.  The problem was introduced by
b566a22c2332 ("PCI: disable Bus Master on PCI device shutdown").

This patch is based on discussion at
http://marc.info/?l=linux-pci&m=138425645204355&w=2

Link: https://bugzilla.kernel.org/show_bug.cgi?id=63861
Reported-by: Chang Liu <cl91tp@gmail.com>
Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: stable@vger.kernel.org	# v3.5+

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 7edd5c3..25f0bc6 100644 (file)
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -19,6 +19,7 @@
 #include <linux/cpu.h>
 #include <linux/pm_runtime.h>
 #include <linux/suspend.h>
+#include <linux/kexec.h>
 #include "pci.h"
 
 struct pci_dynid {
@@ -415,12 +416,17 @@ static void pci_device_shutdown(struct device *dev)
        pci_msi_shutdown(pci_dev);
        pci_msix_shutdown(pci_dev);
 
+#ifdef CONFIG_KEXEC
        /*
-        * Turn off Bus Master bit on the device to tell it to not
-        * continue to do DMA. Don't touch devices in D3cold or unknown states.
+        * If this is a kexec reboot, turn off Bus Master bit on the
+        * device to tell it to not continue to do DMA. Don't touch
+        * devices in D3cold or unknown states.
+        * If it is not a kexec reboot, firmware will hit the PCI
+        * devices with big hammer and stop their DMA any way.
         */
-       if (pci_dev->current_state <= PCI_D3hot)
+       if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot))
                pci_clear_master(pci_dev);
+#endif
 }
 
 #ifdef CONFIG_PM

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d78d28a..5fd33dc 100644 (file)
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -198,6 +198,9 @@ extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
 extern size_t vmcoreinfo_size;
 extern size_t vmcoreinfo_max_size;
 
+/* flag to track if kexec reboot is in progress */
+extern bool kexec_in_progress;
+
 int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
                unsigned long long *crash_size, unsigned long long *crash_base);
 int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 490afc0..d0d8fca 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -47,6 +47,9 @@ u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
 size_t vmcoreinfo_size;
 size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
 
+/* Flag to indicate we are going to kexec a new kernel */
+bool kexec_in_progress = false;
+
 /* Location of the reserved area for the crash kernel */
 struct resource crashk_res = {
        .name  = "Crash kernel",
@@ -1675,6 +1678,7 @@ int kernel_kexec(void)
        } else
 #endif
        {
+               kexec_in_progress = true;
                kernel_restart_prepare(NULL);
                printk(KERN_EMERG "Starting new kernel\n");
                machine_shutdown();