On Mon, Oct 17, 2011 at 12:46 PM, Eric W. Biederman
<ebiederm@xxxxxxxxxxxx> wrote:
>
> I traced a nasty kexec on panic boot failure to the fact that we had
> screaming msi interrupts and we were not disabling the msi messages at
> kernel startup. The booting kernel had not enabled those interupts so
> was not prepared to handle them.
>
> I can see no reason why we would ever want to leave the msi interrupts
> enabled at boot if something else has enabled those interrupts. The pci
> spec specifies that msi interrupts should be off by default. Drivers
> are expected to enable the msi interrupts if they want to use them. Our
> interrupt handling code reprograms the interrupt handlers at boot and
> will not be be able to do anything useful with an unexpected interrupt.
>
> This patch applies cleanly all of the way back to 2.6.32 where I noticed
> the problem.
>
> Cc: stable@xxxxxxxxxx
>
> Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> ---
> drivers/pci/msi.c | 10 ++++++++++
> 1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 2f10328..e174982 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -869,5 +869,15 @@ EXPORT_SYMBOL(pci_msi_enabled);
>
> void pci_msi_init_pci_dev(struct pci_dev *dev)
> {
> + int pos;
> INIT_LIST_HEAD(&dev->msi_list);
> +
> + /* Disable the msi hardware to avoid screaming interrupts
> + * during boot. This is the power on reset default so
> + * usually this should be a noop.
> + */
> + pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
> + if (pos)
> + msi_set_enable(dev, pos, 0);
> + msix_set_enable(dev, 0);
> }
We only build msi.o if CONFIG_PCI_MSI=y, but don't you want to disable
these even if the new kernel has CONFIG_PCI_MSI=n?
Bjorn
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