On Mon, Oct 04, 2010 at 05:56:24PM +0200, Gleb Natapov wrote:
> If a guest accesses swapped out memory do not swap it in from vcpu thread
> context. Schedule work to do swapping and put vcpu into halted state
> instead.
>
> Interrupts will still be delivered to the guest and if interrupt will
> cause reschedule guest will continue to run another task.
>
> Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 17 +++
> arch/x86/kvm/Kconfig | 1 +
> arch/x86/kvm/Makefile | 1 +
> arch/x86/kvm/mmu.c | 51 +++++++++-
> arch/x86/kvm/paging_tmpl.h | 4 +-
> arch/x86/kvm/x86.c | 109 +++++++++++++++++++-
> include/linux/kvm_host.h | 31 ++++++
> include/trace/events/kvm.h | 88 ++++++++++++++++
> virt/kvm/Kconfig | 3 +
> virt/kvm/async_pf.c | 220 +++++++++++++++++++++++++++++++++++++++
> virt/kvm/async_pf.h | 36 +++++++
> virt/kvm/kvm_main.c | 57 ++++++++--
> 12 files changed, 603 insertions(+), 15 deletions(-)
> create mode 100644 virt/kvm/async_pf.c
> create mode 100644 virt/kvm/async_pf.h
>
> + async_pf_cache = NULL;
> +}
> +
> +void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
> +{
> + INIT_LIST_HEAD(&vcpu->async_pf.done);
> + INIT_LIST_HEAD(&vcpu->async_pf.queue);
> + spin_lock_init(&vcpu->async_pf.lock);
> +}
> +
> +static void async_pf_execute(struct work_struct *work)
> +{
> + struct page *page;
> + struct kvm_async_pf *apf =
> + container_of(work, struct kvm_async_pf, work);
> + struct mm_struct *mm = apf->mm;
> + struct kvm_vcpu *vcpu = apf->vcpu;
> + unsigned long addr = apf->addr;
> + gva_t gva = apf->gva;
> +
> + might_sleep();
> +
> + use_mm(mm);
> + down_read(&mm->mmap_sem);
> + get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL);
> + up_read(&mm->mmap_sem);
> + unuse_mm(mm);
> +
> + spin_lock(&vcpu->async_pf.lock);
> + list_add_tail(&apf->link, &vcpu->async_pf.done);
> + apf->page = page;
> + spin_unlock(&vcpu->async_pf.lock);
This can fail, and apf->page become NULL.
> + if (list_empty_careful(&vcpu->async_pf.done))
> + return;
> +
> + spin_lock(&vcpu->async_pf.lock);
> + work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
> + list_del(&work->link);
> + spin_unlock(&vcpu->async_pf.lock);
> +
> + kvm_arch_async_page_present(vcpu, work);
> +
> +free:
> + list_del(&work->queue);
> + vcpu->async_pf.queued--;
> + put_page(work->page);
> + kmem_cache_free(async_pf_cache, work);
> +}
Better handle it here (and other sites).
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