linux-kernel - Re: [RFC] [Patch] calgary iommu: Use the first kernel's tce tables in kdump

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Date:	Wed, 12 Mar 2008 11:58:20 +0200
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Chandru <chandru@...ibm.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, jdmason@...zu.us
Subject: Re: [RFC] [Patch] calgary iommu: Use the first kernel's tce tables
	in kdump

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.

Cheers,
Muli
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