Re: [RFC 2/2] KVM: add initial support for ioregionfd blocking read/write operations

[Elena Afanasova <eafanasova@gmail.com>]

On Thu, 2020-12-31 at 11:46 +0800, Jason Wang wrote:
> On 2020/12/29 下午6:02, Elena Afanasova wrote:
> > Signed-off-by: Elena Afanasova<eafanasova@gmail.com>
> > ---
> >   virt/kvm/ioregion.c | 157
> > ++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 157 insertions(+)
> > 
> > diff --git a/virt/kvm/ioregion.c b/virt/kvm/ioregion.c
> > index a200c3761343..8523f4126337 100644
> > --- a/virt/kvm/ioregion.c
> > +++ b/virt/kvm/ioregion.c
> > @@ -4,6 +4,33 @@
> >   #include <kvm/iodev.h>
> >   #include "eventfd.h"
> >   
> > +/* Wire protocol */
> > +struct ioregionfd_cmd {
> > +	__u32 info;
> > +	__u32 padding;
> > +	__u64 user_data;
> > +	__u64 offset;
> > +	__u64 data;
> > +};
> > +
> 
> I wonder do we need a seq in the protocol. It might be useful if we 
> allow a pair of file descriptors to be used for multiple different
> ranges.
> 
I think it might be helpful in the case of out-of-order requests. 
In the case of in order requests seq field seems not to be necessary
since there will be cmds/replies serialization. I’ll include the
synchronization code in a RFC v2 series.

> Thanks
> 
> 
> > +struct ioregionfd_resp {
> > +	__u64 data;
> > +	__u8 pad[24];
> > +};