Re: [PATCH v11 02/10] iommu/vt-d: Items required for kdump
From: Dave Young
Date: Wed May 13 2015 - 04:43:30 EST
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.
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