Re: [Xen-devel] [PATCH] Allow programatic iomem permissions

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 13/7/07 14:03, "Kieran Mansley" <kmansley@xxxxxxxxxxxxxx> wrote:

>> The issue is that the granter is informed that the grant is released before
>> stale grantee TLB entries are flushed. If the grantee is multi-vcpu then he
>> could theoretically still access a granted page via a stale TLB entry after
>> the granter has recycled the page. The window is extremely tiny though! The
>> correct fix is to reorder the unmap operation to be unmap-list-of-grants
>> then TLB-flush then update-grant-entries-to-indicate-release. Then the whole
>> problem disappears.
> 
> OK, that makes sense, and doesn't at first impression look too hard to
> rectify.
> 
> Am I right in thinking that it's the shared grant table entry that is
> the critical one in this sense (as opposed to the "active" entry).

That's correct.

 -- Keir


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