On Thu, Jul 08, 2010 at 12:59:20PM -0300, Marcelo Tosatti wrote:
> > +static int apf_put_user(struct kvm_vcpu *vcpu, u32 val)
> > +{
> > + if (unlikely(vcpu->arch.apf_memslot_ver !=
> > + vcpu->kvm->memslot_version)) {
> > + u64 gpa = vcpu->arch.apf_msr_val & ~0x3f;
> > + unsigned long addr;
> > + int offset = offset_in_page(gpa);
> > +
> > + addr = gfn_to_hva(vcpu->kvm, gpa >> PAGE_SHIFT);
> > + vcpu->arch.apf_data = (u32 __user*)(addr + offset);
> > + if (kvm_is_error_hva(addr)) {
> > + vcpu->arch.apf_data = NULL;
> > + return -EFAULT;
> > + }
> > + }
> > +
> > + return put_user(val, vcpu->arch.apf_data);
> > +}
>
> Why not use kvm_write_guest?
Because I want to cache gfn_to_hva() translation, so this code tracks
memslot changes and does translation only when needed (almost never).
>
> > +int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
> > + struct kvm_arch_async_pf *arch)
> > +{
> > + struct kvm_async_pf *work;
> > +
> > + if (vcpu->async_pf_queued >= ASYNC_PF_PER_VCPU)
> > + return 0;
> > +
> > + /* setup slow work */
> > +
> > + /* do alloc atomic since if we are going to sleep anyway we
> > + may as well sleep faulting in page */
> > + work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
> > + if (!work)
> > + return 0;
>
> GFP_KERNEL is fine for this context.
But it can sleep, no? The comment explains why I don't want to sleep
here.
--
Gleb.
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