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? 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();
