Re: [Xen-devel] [PATCH RFC 5/4] x86: #PF error code adjustments

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 11/11/15 08:33, Jan Beulich wrote:
> Add a definition for the (for now unused) protection key related error
> code bit, moving our own custom ones out of the way. In the course of
> checking the uses of the latter I realized that while right now they
> can only get set on their own, callers would better not depend on that
> property and check just for the bit rather than matching the entire
> value.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

For the code presented, Reviewed-by: Andrew Cooper
<andrew.cooper3@xxxxxxxxxx>

> ---
> RFC because I noticed that nothing seems to ever set PFEC_page_paged,
> so I wonder whether we really need that flag.

It is set in hap_p2m_ga_to_gfn() for frames with types of P2M_PAGING_TYPES

Did you miss this, or wish to imply that it is actually dead code?

>
> It also seems to me that the part of paging_gva_to_gfn() dealing with
> the nested case can't be quite right: Neither is there any check after
> mode->gva_to_gfn() (namely ignoring INVALID_GFN being returned), nor
> does the handling of the two involved error code values seem
> reasonable. One of the many reasons why nested HVM can't be expected to
> reach "supported" state any time soon, I guess.

I concur.  Yet another item on the "nested" todo list.

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