On 11/27/2013 12:38 PM, ebiederm at xmission.com wrote: > Khalid Aziz <khalid.aziz at oracle.com> writes: > >> Add a flag to tell the PCI subsystem that kernel is shutting down >> in prepapration 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 https://bugzilla.kernel.org/show_bug.cgi?id=63861 >> and avoids any other issues caused by clearing Bus Master bit on PCI >> devices in normal shutdown path. This patch is based on discussion at >> http://marc.info/?l=linux-pci&m=138425645204355&w=2 > > Scratches head. > > Given that most devices already call pci_disable_device which clears the > bus master bit how does this change anything meaningful? > > Is is the problem here that most drivers are lazy and have a noop > shutdown method? Yes, that is exactly the problem. -- Khalid > > Eric > > >> Signed-off-by: Khalid Aziz <khalid.aziz at oracle.com> >> Acked-by: Konstantin Khlebnikov <koct9i at gmail.com> >> Cc: stable at vger.kernel.org >> --- >> drivers/pci/pci-driver.c | 9 ++++++--- >> drivers/pci/pci.h | 3 +++ >> kernel/kexec.c | 4 ++++ >> 3 files changed, 13 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c >> index 9042fdb..e920195 100644 >> --- a/drivers/pci/pci-driver.c >> +++ b/drivers/pci/pci-driver.c >> @@ -400,10 +400,13 @@ static void pci_device_shutdown(struct device *dev) >> pci_msix_shutdown(pci_dev); >> >> /* >> - * 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); >> } >> >> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h >> index 9c91ecc..7d85733 100644 >> --- a/drivers/pci/pci.h >> +++ b/drivers/pci/pci.h >> @@ -9,6 +9,9 @@ >> extern const unsigned char pcix_bus_speed[]; >> extern const unsigned char pcie_link_speed[]; >> >> +/* flag to track if kexec reboot is in progress */ >> +extern unsigned long kexec_in_progress; >> + >> /* Functions internal to the PCI core code */ >> >> int pci_create_sysfs_dev_files(struct pci_dev *pdev); >> diff --git a/kernel/kexec.c b/kernel/kexec.c >> index 490afc0..fd2d63e 100644 >> --- 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 */ >> +unsigned long kexec_in_progress = 0; >> + >> /* 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 = 1; >> kernel_restart_prepare(NULL); >> printk(KERN_EMERG "Starting new kernel\n"); >> machine_shutdown();
