linux-kernel - Re: [PATCH] pci: let pci_device_shutdown to call pci_disable

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Message-ID: <86802c440804231822s7cc4e2c1vfdb7f40ae0580045@mail.gmail.com>
Date:	Wed, 23 Apr 2008 18:22:22 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	michael@...erman.id.au
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	"Greg KH" <greg@...ah.com>, "David Miller" <davem@...emloft.net>,
	"Jeff Garzik" <jeff@...zik.org>,
	linux-pci <linux-pci@...ey.karlin.mff.cuni.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"James Bottomley" <James.Bottomley@...senpartnership.com>,
	"Sathya Prakash" <sathya.prakash@....com>
Subject: Re: [PATCH] pci: let pci_device_shutdown to call pci_disable_msi

On Wed, Apr 23, 2008 at 5:17 PM, Michael Ellerman
<michael@...erman.id.au> wrote:
> On Wed, 2008-04-23 at 06:08 -0700, Eric W. Biederman wrote:
>  > Michael Ellerman <michael@...erman.id.au> writes:
>  >
>  > > On Tue, 2008-04-22 at 21:48 -0700, Yinghai Lu wrote:
>  > >> this change
>  > >>
>  > >> | commit 23a274c8a5adafc74a66f16988776fc7dd6f6e51
>  > >> | Author: Prakash, Sathya <sathya.prakash@....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@....com>
>  > >> |     Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.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.
>
>  But does that help us? What if the device driver in the 2nd kernel
>  assumes it's using INTX, when in fact MSI is enabled on the device. In
>  that case none of the MSI code will even be called AFAIK.

ok. for kdump case, if driver can not use msi (?), with pci=nomsi
we need to call pci_intx_for_msi(dev, 1) at beginning of second kernel.

will produce another patch about that case.

YH
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