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SubjectRe: [PATCH v6 12/12] KVM: indicate readonly access fault
On 09/11/2012 05:39 PM, Marcelo Tosatti wrote:
> On Tue, Sep 11, 2012 at 12:18:22PM +0300, Avi Kivity wrote:
>> > The same can happen with slot deletion, for example.
>> >
>> > Userspace (which performed the modification which can result in faults
>> > to non-existant/read-only/.../new-tag memslot), must handle the faults
>> > properly or avoid the possibility for reference to memslot information
>> > from the past.
>> >
>> > I think its worthwhile to add a note about this in the API
>> > documentation: "The user of this interface is responsible for handling
>> > references to stale memslot information, either by handling
>> > exit notifications which reference stale memslot information or not
>> > allowing these notifications to exist by stopping all vcpus in userspace
>> > before performing modifications to the memslots map".
>>
>> Or we can drop the new interface and rely on userspace to perform the
>> lookup under its own locking rules.
>>
>> It's slow, but writes to ROM or ROM/device are rare anyway.
>
> Lookup what information?

Where to dispatch the write.

In fact userspace has to do that anyway if it's a ROM/device. There's
no way userspace can guess that unless we pass in the slot number (which
isn't synchronized with anything).


--
error compiling committee.c: too many arguments to function


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