Re: [Xen-devel] [PATCH RFC 2/4] xen: grant_table: implement grant_table_soft_reset()

[Tim Deegan <tim@xxxxxxx>]

At 15:35 +0200 on 03 Jun (1433345720), Vitaly Kuznetsov wrote:
> When soft reset is being performed we need to replace all actively
> granted pages with empty pages to prevent possible future memory
> corruption as the newly started kernel won't be aware of these
> granted pages.

I'm not sure about this one.  IMO it's the guest's responsibility to
find and disable whatever holds these grants.  This is by analogy with
a bus-master-capable device in a real PC: until the device is found
and reset, the new OS can't use memory outside its guaranteed safe
pool.

There has been talk before of an operation along the lines of "revoke
this grant entry and wait for all users to release it" but that would
only help with backends that are guaranteed to release grants in a
reasonable time.

Cheers,

Tim.

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