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    SubjectRe: [PATCH 3/5] vhost: support upto 509 memory regions
    On Thu, Jun 18, 2015 at 01:50:32PM +0200, Paolo Bonzini wrote:
    >
    >
    > On 18/06/2015 13:41, Michael S. Tsirkin wrote:
    > > On Thu, Jun 18, 2015 at 01:39:12PM +0200, Igor Mammedov wrote:
    > >> Lets leave decision upto users instead of making them live with
    > >> crashing guests.
    > >
    > > Come on, let's fix it in userspace.
    >
    > It's not trivial to fix it in userspace. Since QEMU uses RCU there
    > isn't a single memory map to use for a linear gpa->hva map.

    Could you elaborate?

    I'm confused by this mention of RCU.
    You use RCU for accesses to the memory map, correct?
    So memory map itself is a write side operation, as such all you need to
    do is take some kind of lock to prevent conflicting with other memory
    maps, do rcu sync under this lock.


    > I find it absurd that we're fighting over 12K of memory.
    >
    > Paolo

    I wouldn't worry so much if it didn't affect kernel/userspace API.
    Need to be careful there.

    --
    MST


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