Re: [PATCH 01/11] Add shared memory hypercall to PV Linux guest.
From: Gleb Natapov
Date: Mon Nov 02 2009 - 02:07:39 EST
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
> 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
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.
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