Re: [PATCH V4 14/24] arm/ioreq: Introduce arch specific bits for IOREQ/DM features

[Oleksandr <olekstysh@xxxxxxxxx>]

On 20.01.21 21:47, Stefano Stabellini wrote:

Hi Julien, Stefano


> On Wed, 20 Jan 2021, Julien Grall wrote:
> > Hi Stefano,
> >
> > On 20/01/2021 00:50, Stefano Stabellini wrote:
> > > On Tue, 19 Jan 2021, Oleksandr wrote:
> > > > diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c
> > > > index 40b9e59..0508bd8 100644
> > > > --- a/xen/arch/arm/ioreq.c
> > > > +++ b/xen/arch/arm/ioreq.c
> > > > @@ -101,12 +101,10 @@ enum io_state try_fwd_ioserv(struct cpu_user_regs
> > > > *regs,
> > > >
> > > >    bool arch_ioreq_complete_mmio(void)
> > > >    {
> > > > -    struct vcpu *v = current;
> > > >        struct cpu_user_regs *regs = guest_cpu_user_regs();
> > > >        const union hsr hsr = { .bits = regs->hsr };
> > > > -    paddr_t addr = v->io.req.addr;
> > > >
> > > > -    if ( try_handle_mmio(regs, hsr, addr) == IO_HANDLED )
> > > > +    if ( handle_ioserv(regs, current) == IO_HANDLED )
> > > >        {
> > > >            advance_pc(regs, hsr);
> > > >            return true;
> > > Yes, but I think we want to keep the check
> > >
> > >       vio->req.state == STATE_IORESP_READY
> > >
> > > So maybe (uncompiled, untested):
> > >
> > >       if ( v->io.req.state != STATE_IORESP_READY )
> > >           return false;
> > Is it possible to reach this function with v->io.req.state !=
> > STATE_IORESP_READY? If not, then I would suggest to add an
> > ASSERT_UNREACHABLE() before the return.
> If I am reading the state machine right it should *not* be possible to
> get here with v->io.req.state != STATE_IORESP_READY, so yes,
> ASSERT_UNREACHABLE() would work.
Agree here. If the assumption is not correct (unlikely), I think I will 
catch this during testing.
In addition, we can probably drop case STATE_IORESP_READY in 
try_fwd_ioserv().

[not tested]


diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c
index 40b9e59..c7ee1a7 100644
--- a/xen/arch/arm/ioreq.c
+++ b/xen/arch/arm/ioreq.c
@@ -71,9 +71,6 @@ enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
     case STATE_IOREQ_NONE:
         break;

-    case STATE_IORESP_READY:
-        return IO_HANDLED;
-
     default:
         gdprintk(XENLOG_ERR, "wrong state %u\n", vio->req.state);
         return IO_ABORT;
@@ -104,9 +101,14 @@ bool arch_ioreq_complete_mmio(void)
     struct vcpu *v = current;
     struct cpu_user_regs *regs = guest_cpu_user_regs();
     const union hsr hsr = { .bits = regs->hsr };
-    paddr_t addr = v->io.req.addr;

-    if ( try_handle_mmio(regs, hsr, addr) == IO_HANDLED )
+    if ( v->io.req.state != STATE_IORESP_READY )
+    {
+        ASSERT_UNREACHABLE();
+        return false;
+    }
+
+    if ( handle_ioserv(regs, v) == IO_HANDLED )
     {
         advance_pc(regs, hsr);
         return true;


--
Regards,

Oleksandr Tyshchenko