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Re: [PATCH 4/9] gnttab: drop GNTMAP_can_fail


  • To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Thu, 26 Aug 2021 12:45:04 +0100
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On 26/08/2021 11:13, Jan Beulich wrote:
> There's neither documentation of what this flag is supposed to mean, nor
> any implementation. With this, don't even bother enclosing the #define-s
> in a __XEN_INTERFACE_VERSION__ conditional, but drop them altogether.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

It was introduced in 4d45702cf0398 along with GNTST_eagain, and the
commit message hints that it is for xen-paging

Furthermore, the first use of GNTST_eagain was in ecb35ecb79e0 for
trying to map/copy a paged-out frame.

Therefore I think it is reasonable to conclude that there was a planned
interaction between GNTMAP_can_fail and paging, which presumably would
have been "don't pull this in from disk if it is paged out".


I think it is fine to drop, as no implementation has ever existed in
Xen, but it would be helpful to have the history summarised in the
commit message.

~Andrew




 


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