linux-kernel - Re: [PATCH v11 02/10] iommu/vt-d: Items required for kdump

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Message-ID: <20150513084226.GO4561@localhost.localdomain>
Date:	Wed, 13 May 2015 16:42:26 +0800
From:	Dave Young <dyoung@...hat.com>
To:	"Li, ZhenHua" <zhen-hual@...com>
Cc:	dwmw2@...radead.org, indou.takao@...fujitsu.com, bhe@...hat.com,
	joro@...tes.org, vgoyal@...hat.com,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kexec@...ts.infradead.org,
	alex.williamson@...hat.com, ddutile@...hat.com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, jerry.hoemann@...com, tom.vaden@...com,
	li.zhang6@...com, lisa.mitchell@...com, billsumnerlinux@...il.com,
	rwright@...com
Subject: Re: [PATCH v11 02/10] iommu/vt-d: Items required for kdump

On 05/13/15 at 09:45am, Li, ZhenHua wrote:
> On 05/12/2015 04:17 PM, Dave Young wrote:
> >On 05/11/15 at 05:52pm, Li, Zhen-Hua wrote:
> >>Add context entry functions needed for kdump.
> >>+/*
> >>+ * Fix Crashdump failure caused by leftover DMA through a hardware IOMMU
> >>+ *
> >>+ * Fixes the crashdump kernel to deal with an active iommu and legacy
> >>+ * DMA from the (old) panicked kernel in a manner similar to how legacy
> >>+ * DMA is handled when no hardware iommu was in use by the old kernel --
> >>+ * allow the legacy DMA to continue into its current buffers.
> >>+ *
> >>+ * In the crashdump kernel, this code:
> >>+ * 1. skips disabling the IOMMU's translating.
> >>+ * 2. Do not re-enable IOMMU's translating.
> >>+ * 3. In kdump kernel, use the old root entry table.
> >>+ * 4. Allocate pages for new context entry, copy data from old context entries
> >>+ *    in the old kernel to the new ones.
> >>+ *
> >>+ * In other kinds of kernel, for example, a kernel started by kexec,
> >>+ * do the same thing as crashdump kernel.
> >>+ */
> >>+
> >>+
> >
> >Above comments should come along with the code changes instead of putting it
> >in this patch.
> >
> >BTW, there's one more blank line at the end..
> Code change is in 00/10, the cover letter.

I means the real code, not the changelog.

> And the blank does not matter, I checked the patch with
> scripts/checkpatch.pl,  no warnings, no errors.

Why add two line breaks if one is enough? Adding such check in checkpatch.pl
make sense to me actually.

Thanks
Dave
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