Re: [PATCH v2 1/4] xen/io: provide helpers for multi size MMIO accesses

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Apr 17, 2025 at 09:43:09AM +0200, Jan Beulich wrote:
> On 15.04.2025 17:32, Roger Pau Monne wrote:
> > @@ -5115,7 +5115,6 @@ static void subpage_mmio_write_emulate(
> >  
> >      if ( test_bit(offset / MMIO_RO_SUBPAGE_GRAN, entry->ro_elems) )
> >      {
> > - write_ignored:
> >          gprintk(XENLOG_WARNING,
> >                  "ignoring write to R/O MMIO 0x%"PRI_mfn"%03x len %u\n",
> >                  mfn_x(mfn), offset, len);
> > @@ -5131,26 +5130,7 @@ static void subpage_mmio_write_emulate(
> >          return;
> >      }
> >  
> > -    addr += offset;
> > -    switch ( len )
> > -    {
> > -    case 1:
> > -        writeb(*(const uint8_t*)data, addr);
> > -        break;
> > -    case 2:
> > -        writew(*(const uint16_t*)data, addr);
> > -        break;
> > -    case 4:
> > -        writel(*(const uint32_t*)data, addr);
> > -        break;
> > -    case 8:
> > -        writeq(*(const uint64_t*)data, addr);
> > -        break;
> > -    default:
> > -        /* mmio_ro_emulated_write() already validated the size */
> > -        ASSERT_UNREACHABLE();
> > -        goto write_ignored;
> > -    }
> > +    write_mmio(addr + offset, data, len);
> >  }
> 
> Should probably have noticed this on v1 already: The log message is now lost
> for the write-ignored case. It looks easy enough to have the function return
> a boolean indicating "done", to retain original behavior here.

Hm, I didn't seem to me the message wants conserving, as it's
unreachable code.  I can try to add again, but we don't print such
message in other cases.

Thanks, Roger.