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Re: [Xen-devel] [PATCH 2/2] xen: arm: Set all bits in mfn_to_xen_entry()

On 17/08/2015 11:58, Chris (Christopher) Brand wrote:
Hi Julien,

Thanks for the review.

+            .pxn = 0,

I would add a comment to explain that this bit is reserved for PL2 stage
1 page table.

Will do.

+            .avail = 0,

I don't think this one is necessary. avail is not used by the hardware neither

"grep -rF pt.avail xen" gives 7 matches in xen/arch/arm/mm.c, so it is used by
Xen (I'll fully admit that I didn't dig in to the "how and why" of its use).

Hmmm right. Sorry I haven't check the Xen code for that.

It's used for domheap mapping to know how many times it has been referenced.

what about *t fields (pxnt, xnt, apt,...)?

I figured that as we're setting table to 0, these are ignored, and any code 
table to 1 should then set them. I can obviously easily set them here (I guess 
to zero would make sense) if you think it's worthwhile ...

It was just an open question. :) I'm not sure what we should do with them.


Julien Grall

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