Re: [Xen-devel] [PATCH 1/1] xen-hvm.c: Add support for Xen access to vmport

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 29 Sep 2014, Stefano Stabellini wrote:
> On Fri, 26 Sep 2014, Don Slutz wrote:
> > This adds synchronisation of the vcpu registers
> > between Xen and QEMU.
> > 
> > Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> 
> [...]
> 
> > diff --git a/xen-hvm.c b/xen-hvm.c
> > index 05e522c..e1274bb 100644
> > --- a/xen-hvm.c
> > +++ b/xen-hvm.c
> > @@ -857,14 +857,48 @@ static void cpu_handle_ioreq(void *opaque)
> >  
> >      handle_buffered_iopage(state);
> >      if (req) {
> > +#ifdef IOREQ_TYPE_VMWARE_PORT
> 
> Is there any reason to #ifdef this code?
> Couldn't we just always build it in QEMU?
> 
> 
> > +        if (req->type == IOREQ_TYPE_VMWARE_PORT) {
> 
> I think it would make more sense to check for IOREQ_TYPE_VMWARE_PORT
> from within handle_ioreq.
> 
> 
> > +            CPUX86State *env;
> > +            ioreq_t fake_req = {
> > +                .type = IOREQ_TYPE_PIO,
> > +                .addr = (uint16_t)req->size,
> > +                .size = 4,
> > +                .dir = IOREQ_READ,
> > +                .df = 0,
> > +                .data_is_ptr = 0,
> > +            };

Why do you need a fake req?
Couldn't Xen send the real req instead? If any case you should spend a
few more words on why you are doing this.


> > +            if (!xen_opaque_env) {
> > +                xen_opaque_env = g_malloc(sizeof(CPUX86State));
> > +            }
> > +            env = xen_opaque_env;
> > +            env->regs[R_EAX] = (uint32_t)(req->addr >> 32);
> > +            env->regs[R_EBX] = (uint32_t)(req->addr);
> > +            env->regs[R_ECX] = req->count;
> > +            env->regs[R_EDX] = req->size;
> > +            env->regs[R_ESI] = (uint32_t)(req->data >> 32);
> > +            env->regs[R_EDI] = (uint32_t)(req->data);
> > +            handle_ioreq(&fake_req);
> > +            req->addr = ((uint64_t)fake_req.data << 32) |
> > +                (uint32_t)env->regs[R_EBX];
> > +            req->count = env->regs[R_ECX];
> > +            req->size = env->regs[R_EDX];
> > +            req->data = ((uint64_t)env->regs[R_ESI] << 32) |
> > +                (uint32_t)env->regs[R_EDI];
> 
> This code could be moved to a separate helper function called by
> handle_ioreq.
> 
> 
> > +        } else {
> > +            handle_ioreq(req);
> > +        }
> > +#else
> >          handle_ioreq(req);
> > +#endif
> 

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