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    SubjectRe: [PATCH 01/11] Add shared memory hypercall to PV Linux guest.
    On Sun, Nov 01, 2009 at 11:27:15PM -0500, Rik van Riel wrote:
    > On 11/01/2009 06:56 AM, Gleb Natapov wrote:
    > >Add hypercall that allows guest and host to setup per cpu shared
    > >memory.
    >
    > While it is pretty obvious that we should implement
    > the asynchronous pagefaults for KVM, so a swap-in
    > of a page the host swapped out does not stall the
    > entire virtual CPU, I believe that adding extra
    > data accesses at context switch time may not be
    > the best tradeoff.
    >
    > It may be better to simply tell the guest what
    > address is faulting (or give the guest some other
    > random unique number as a token). Then, once the
    > host brings that page into memory, we can send a
    > signal to the guest with that same token.
    >
    > The problem of finding the task(s) associated with
    > that token can be left to the guest. A little more
    > complexity on the guest side, but probably worth it
    > if we can avoid adding cost to the context switch
    > path.
    >
    This is precisely what this series implements. The function below
    is leftover from previous implementation, not used by the rest of the
    patch and removed by a later patch. Just a left over from rebase. Sorry
    about that. Will be fixed for future submissions.

    > >+static void kvm_end_context_switch(struct task_struct *next)
    > >+{
    > >+ struct kvm_vcpu_pv_shm *pv_shm =
    > >+ per_cpu(kvm_vcpu_pv_shm, smp_processor_id());
    > >+
    > >+ if (!pv_shm)
    > >+ return;
    > >+
    > >+ pv_shm->current_task = (u64)next;
    > >+}
    > >+
    >
    >
    >
    > --
    > All rights reversed.

    --
    Gleb.


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