Re: [PATCH] KVM: Add reading critical region for kvm_io_bus_read/write

Sheng Yang
2010-12-07T02:32:33Z

On Monday 06 December 2010 20:58:10 Avi Kivity wrote:
> On 12/06/2010 10:44 AM, Sheng Yang wrote:
> > Seems we missed it.
> >
> > Signed-off-by: Sheng Yang<sheng@linux.intel.com>
> > ---
> > Do we need this, or slot_lock covered this?
> >
> > virt/kvm/kvm_main.c | 24 ++++++++++++++++--------
> > 1 files changed, 16 insertions(+), 8 deletions(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index c4ee364..3e71b91 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -2228,28 +2228,36 @@ static void kvm_io_bus_destroy(struct kvm_io_bus
> > *bus)
> >
> > int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> >
> > int len, const void *val)
> >
> > {
> >
> > - int i;
> > + int i, idx, r = -EOPNOTSUPP;
> >
> > struct kvm_io_bus *bus;
> >
> > + idx = srcu_read_lock(&kvm->srcu);
> >
> > bus = srcu_dereference(kvm->buses[bus_idx],&kvm->srcu);
> > for (i = 0; i< bus->dev_count; i++)
> >
> > - if (!kvm_iodevice_write(bus->devs[i], addr, len, val))
> > - return 0;
> > - return -EOPNOTSUPP;
> > + if (!kvm_iodevice_write(bus->devs[i], addr, len, val)) {
> > + r = 0;
> > + break;
> > + }
> > + srcu_read_unlock(&kvm->srcu, idx);
> > + return r;
> >
> > }
>
> Isn't this already taken care of by srcu_read_lock() in
> vcpu_enter_guest(), just before calling ->handle_exit()?

Yes, finally found it. So big reading critical region...

--
regards
Yang, Sheng