Re: [PATCH] pci: let pci_device_shutdown to call pci_disable_msi

["Yinghai Lu" <yhlu.kernel@gmail.com>]

On Wed, Apr 23, 2008 at 6:08 AM, Eric W. Biederman
<ebiederm@xmission.com> wrote:
> Michael Ellerman <michael@ellerman.id.au> writes:
>
>  > On Tue, 2008-04-22 at 21:48 -0700, Yinghai Lu wrote:
>  >> this change
>  >>
>  >> | commit 23a274c8a5adafc74a66f16988776fc7dd6f6e51
>  >> | Author: Prakash, Sathya <sathya.prakash@lsi.com>
>  >> | Date:   Fri Mar 7 15:53:21 2008 +0530
>  >> |
>  >> |     [SCSI] mpt fusion: Enable MSI by default for SAS controllers
>  >> |
>  >> | This patch modifies the driver to enable MSI by default for all SAS chips.
>  >> |
>  >> |     Signed-off-by: Sathya Prakash <sathya.prakash@lsi.com>
>  >> |     Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
>  >> |
>  >> cause kexec RHEL 5.1 kernel fail.
>  >>
>  >> root casue: the rhel 5.1 kernel still use INTx emulation.
>  >> and mptscsih_shutdown doesn't call pci_disable_msi to reenable INTx on kexec
>  > path
>  >>
>  >> so try to call pci_disable_msi in shutdown patch
>  >
>  > How is kdump going to work? Your shutdown routine won't be called and
>  > you'll have the same problem in the 2nd kernel, won't you?
>
>  Taking a quick look our current msi initialization appears robust in
>  not assuming the state of the msi config bits.
>
>  So the only remaining problem is running older software that
>  assumes the msi config bits are in the state they should be in
>  out of reset.
>
>  YH on that score it appears I goofed a little when I gave you
>  my suggestion on how to fix this in pci_disable_msi.
>
>  If we have crazy hardware that supports multi irqs in with
>  a plain msi capability.  During initialization we mask
>  all of the irqs.
>
>  from msi_capability_init:
>         if (entry->msi_attrib.maskbit) {
>                 unsigned int maskbits, temp;
>                 /* All MSIs are unmasked by default, Mask them all */
>                 pci_read_config_dword(dev,
>                         msi_mask_bits_reg(pos, is_64bit_address(control)),
>                         &maskbits);
>                 temp = (1 << multi_msi_capable(control));
>                 temp = ((temp - 1) & ~temp);
>                 maskbits |= temp;
>                 pci_write_config_dword(dev,
>                         msi_mask_bits_reg(pos, is_64bit_address(control)),
>                         maskbits);
>         }
>
>  So it appears to truly return to the reset state we should unmask
>  them all, instead of just that one.  Not that it matters in practice,
>  but handling that corner case would be polite.

will extend that a little bit.

YH