Re: [Xen-devel] [PATCH V3 1/3] xen/mem_access: Support for memory-content hiding

["Lengyel, Tamas" <tlengyel@xxxxxxxxxxx>]

On Tue, Jul 7, 2015 at 9:21 AM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> wrote:

On 07/07/2015 04:15 PM, Lengyel, Tamas wrote:
>
>
> On Tue, Jul 7, 2015 at 9:09 AM, Razvan Cojocaru
> <rcojocaru@xxxxxxxxxxxxxxx <mailto:rcojocaru@xxxxxxxxxxxxxxx>> wrote:
>
>     So VM_EVENT_FLAG_FOREIGN (1 << 1), and then MEM_ACCESS_EMULATE (1 << 6).
>     Now you're adding VM_EVENT_FLAG_TOGGLE_SINGLESTEP (1 << 2), and if we're
>     not very careful, slowly but surely the VM_EVENT_FLAG_ constants will
>     crawl towards (1 << 6) and start overlapping with MEM_ACCESS_EMULATE,
>     MEM_ACCESS_EMULATE_NOWRITE and so on, because they're not clearly
>     #defined right after the rest of the VM_EVENT_FLAG_ ones, are called
>     MEM_ACCESS_<something> just like the mem_access event specific flags,
>     and they use bit shifts relative to the MEM_ACCESS_ ones as well. This
>     is in part what has caused my confusion here.
>
>     What do you think?
>
>     Thanks,
>     Razvan
>
>
> Well, this is clearly an oversight that we need to fix. MEM_ACCESS_*
> flags should be only set on the mem_access flags field.

Right, if there are no objections, I'll just submit a small patch (in a
few minutes) that moves MEM_ACCESS_EMULATE and
MEM_ACCESS_EMULATE_NOWRITE up near the VM_EVENT_FLAG_ constants, and
renames them VM_EVENT_FLAG_EMULATE and VM_EVENT_FLAG_EMULATE_NOWRITE.

It seems like this would be a pretty straightforward change, so I assume
it's likely to go in fast.


Thanks,
Razvan

Sounds good. Probably it shouldn't take long to land that small fix in staging. But we will have conflicts as my patches introduce new VM_EVENT_FLAGs too so depending on the order of things, it's a PITA ;)

Tamas

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