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    SubjectRe: [PATCH v3 00/12] KVM: Add host swap event notifications for PV guest
    On Tue, Jan 5, 2010 at 11:12 PM, Gleb Natapov <> wrote:
    > KVM virtualizes guest memory by means of shadow pages or HW assistance
    > like NPT/EPT. Not all memory used by a guest is mapped into the guest
    > address space or even present in a host memory at any given time.
    > When vcpu tries to access memory page that is not mapped into the guest
    > address space KVM is notified about it. KVM maps the page into the guest
    > address space and resumes vcpu execution. If the page is swapped out
    > from host memory vcpu execution is suspended till the page is not swapped
    > into the memory again. This is inefficient since vcpu can do other work
    > (run other task or serve interrupts) while page gets swapped in.
    > To overcome this inefficiency this patch series implements "asynchronous
    > page fault" for paravirtualized KVM guests. If a page that vcpu is
    > trying to access is swapped out KVM sends an async PF to the vcpu
    > and continues vcpu execution. Requested page is swapped in by another
    > thread in parallel.  When vcpu gets async PF it puts faulted task to
    > sleep until "wake up" interrupt is delivered. When the page is brought
    > to the host memory KVM sends "wake up" interrupt and the guest's task
    > resumes execution.

    Is it true that to make this work, we will need a (PV) kernel driver
    for each guest OS (Windows, Linux, ...)?

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