Messages in this thread Patch in this message | | | Date | Fri, 18 Jan 2013 11:16:27 -0500 | From | Don Dutile <> | Subject | Re: [PATCH 4/5] PCI: don't touch enable_cnt in pci_device_shutdown() |
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On 01/18/2013 06:42 AM, Konstantin Khlebnikov wrote: > comment in commit b566a22c23327f18ce941ffad0ca907e50a53d41 > ("PCI: disable Bus Master on PCI device shutdown") says: > > | Disable Bus Master bit on the device in pci_device_shutdown() to ensure PCI > | devices do not continue to DMA data after shutdown. This can cause memory > | corruption in case of a kexec where the current kernel shuts down and > | transfers control to a new kernel while a PCI device continues to DMA to > | memory that does not belong to it any more in the new kernel. > > Seems like pci_clear_master() must be used here instead of pci_disable_device(), > because it disables Bus Muster unconditionally and doesn't changes enable_cnt. > > Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org> > Cc: linux-pci@vger.kernel.org > Cc: Bjorn Helgaas<bhelgaas@google.com> > Cc: Khalid Aziz<khalid.aziz@hp.com>
Hmmm.... wondering if this was the problem why kexec folks said that device_shutdown() didn't work on all systems (when trying to stop DMA, esp. on IOMMU-enabled systems...).
Bjorn: do you have a list &/or contact in kexec space to try this patch vs the "reset every PCI bus" strategy that is currently being pushed for kexec's method to halt DMA from a PCI device ?
> --- > drivers/pci/pci-driver.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 030dbf0..853d605 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -392,7 +392,7 @@ static void pci_device_shutdown(struct device *dev) > * Turn off Bus Master bit on the device to tell it to not > * continue to do DMA > */ > - pci_disable_device(pci_dev); > + pci_clear_master(pci_dev); > } > > #ifdef CONFIG_PM > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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