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



On Tue, Jul 26, 2016 at 4:25 AM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> 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.)

No problem, that's fine.

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

Correct, I'm in a -8h time zone compared to most of Europe.

Thanks,
Tamas

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