On Tue, Oct 05, 2010 at 11:59:16AM -0300, Marcelo Tosatti wrote:
> 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).
Yeah. We should just reenter gust and let usual code path handle error
on next guest access.
--
Gleb.
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