On 22/04/14 22:15, Christian Borntraeger wrote: > On 21/04/14 15:25, Oleg Nesterov wrote: >> async_pf_execute() has no reasons to adopt apf->mm, gup(current, mm) >> should work just fine even if current has another or NULL ->mm. >> >> Recently kvm_async_page_present_sync() was added insedie the "use_mm" >> section, but it seems that it doesn't need current->mm too. >> >> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> > > Indeed, use/unuse_mm should only be necessary for copy_to/from_user etc. > This is fine for s390, but it seems that x86 kvm_arch_async_page_not_present > might call apf_put_user which might call copy_to_user, so this is not ok, I guess. wanted to say kvm_arch_async_page_not_present, but I have to correct myself. x86 does the "page is there" in the cpu loop, not in the worker. The cpu look d oes have a valid mm. So this patch should be also ok. > >> --- >> virt/kvm/async_pf.c | 2 -- >> 1 files changed, 0 insertions(+), 2 deletions(-) >> >> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c >> index 10df100..0ced4f3 100644 >> --- a/virt/kvm/async_pf.c >> +++ b/virt/kvm/async_pf.c >> @@ -80,12 +80,10 @@ static void async_pf_execute(struct work_struct *work) >> >> might_sleep(); >> >> - use_mm(mm); >> down_read(&mm->mmap_sem); >> get_user_pages(current, mm, addr, 1, 1, 0, NULL, NULL); >> up_read(&mm->mmap_sem); >> kvm_async_page_present_sync(vcpu, apf); >> - unuse_mm(mm); >> >> spin_lock(&vcpu->async_pf.lock); >> list_add_tail(&apf->link, &vcpu->async_pf.done); >> > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
