Re: [Xen-devel] [PATCH v6] altp2m: Allow shared entries to be copied to altp2m views during lazycopy

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Mon, Jul 25, 2016 at 7:33 PM, Tamas K Lengyel
<tamas.lengyel@xxxxxxxxxxxx> wrote:
> Move sharing locks above altp2m to avoid locking order violation and crashing
> the hypervisor during unsharing operations when altp2m is active.
>
> Applying mem_access settings or remapping gfns in altp2m views will
> automatically unshare the page if it was shared previously and for this we use
> get_entry() wrappers to properly initiate unsharing. Also, disallow nominating
> pages for which there are pre-existing altp2m mem_access settings or 
> remappings
> present. However, allow altp2m to populate altp2m views with shared entries
> during lazycopy as unsharing will automatically propagate the change to these
> entries in altp2m views as well.
>
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>

Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>

If you're OK with it, I hope you don't mind if I change the changelog
text to the following:

---
altp2m: Allow shared entries to be copied to altp2m views during lazycopy

Move sharing locks above altp2m to avoid locking order violation and crashing
the hypervisor during unsharing operations when altp2m is active.

Applying mem_access settings or remapping gfns in altp2m views will
automatically unshare the page if it was shared previously. Also,
disallow nominating pages for which there are pre-existing altp2m
mem_access settings or remappings present. However, allow altp2m to
populate altp2m views with shared entries during lazycopy as unsharing
will automatically propagate the change to these entries in altp2m
views as well.

While we're here, switch to using the appropriate wrappers rather than
calling p2m->get_entry() directly.
---

That separates out the description of the important algorithmic change
of the patch from the purely cosmetic change of using the get_entry()
wrappers; hopefully that should make both easier to grok.

(I'll check it in as above if I don't hear any objections by EOD today.)

 -George

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