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From: Vivek Goyal <vgoyal@redhat.com>
To: Muli Ben-Yehuda <muli@il.ibm.com>
Cc: Chandru <chandru@in.ibm.com>,
	akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	jdmason@kudzu.us
Subject: Re: [RFC] [Patch] calgary iommu: Use the first kernel's tce tables in kdump
Date: Wed, 12 Mar 2008 14:08:06 -0400	[thread overview]
Message-ID: <20080312180806.GB13549@redhat.com> (raw)
In-Reply-To: <20080312095820.GG10790@tyrion.haifa.ibm.com>

On Wed, Mar 12, 2008 at 11:58:20AM +0200, Muli Ben-Yehuda wrote:
> On Wed, Mar 12, 2008 at 10:38:49AM +0530, Chandru wrote:
> 
> > The system booted! , :) with the following change. Muli acceptable??
> >
> > static void calgary_watchdog(unsigned long data)
> > {
> > ...
> > ...
> > /* Disable bus that caused the error and ignore if it's kdump kernel */
> > + if ( !is_kdump_kernel()) {
> > target = calgary_reg(bbar, phb_offset(tbl->it_busno) |
> > PHB_CONFIG_RW_OFFSET);
> > val32 = be32_to_cpu(readl(target));
> > val32 |= PHB_SLOT_DISABLE;
> > writel(cpu_to_be32(val32), target);
> > + }
> > readl(target); /* flush */
> 
> Yikes, not really :-)
> 
> You're basically saying "if we're in a kdump kernel, let's ignore all
> DMA errors and hope for the best". This is not really acceptable. What
> we could do is limit the scope of ignorance - only ignore errors from
> the point the kdump kernel starts booting until we have reinitialized
> the device and then go back to handling DMA errors correctly.
> 

Agree. Ignoring all the DMA errors in kdump kernel does not sound very
good.

On a side note, typically how much time does it take to for DMA operations
to finish. Can we wait for a random amount of time in second kernel,
hoping all the DMA operations are complete, and then setup a new table?

This can be atleast a stop gap solution till we come up with a good
solution?

Thanks
Vivek

  reply	other threads:[~2008-03-12 18:11 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-10-09 20:40 chandru
2007-10-09 21:06 ` Muli Ben-Yehuda
2007-10-10  5:30   ` Vivek Goyal
2007-10-14  5:41     ` Muli Ben-Yehuda
2007-10-15  6:29       ` Vivek Goyal
2007-12-24  5:15         ` Chandru
2008-03-10 13:20           ` Chandru
2008-03-10 16:09             ` Andrew Morton
2008-06-21 12:11               ` Chandru
2008-06-21 12:25                 ` Mark Salyzyn
2008-06-23 19:29                 ` Muli Ben-Yehuda
2008-07-15  8:45                   ` Chandru
2008-07-15 10:52                     ` Muli Ben-Yehuda
2008-07-17 23:14                     ` Andrew Morton
2008-07-20  9:42                       ` Muli Ben-Yehuda
2008-03-11 13:29             ` Vivek Goyal
2008-03-12  5:08               ` Chandru
2008-03-12  9:58                 ` Muli Ben-Yehuda
2008-03-12 18:08                   ` Vivek Goyal [this message]
2008-03-13 15:49                     ` Muli Ben-Yehuda
2007-10-10  5:37 ` Vivek Goyal

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