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

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Tue, Jul 26, 2016 at 10:35 AM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> 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.)

Sorry, suddenly remembered that you're actually *not* in a European
time zone (IIRC); I'll wait until tomorrow morning.

 -George

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