Re: [Xen-devel] [PATCH] VT-d: should not disable VT-d when find unknown DMAR structure type

[Weidong Han <weidong.han@xxxxxxxxx>]

Nadolski, Ed wrote:
> > -----Original Message-----
> > From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> > bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Han, Weidong
> > Sent: Thursday, March 25, 2010 3:41 AM
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Cc: Kay, Allen M; Keir Fraser
> > Subject: [Xen-devel] [PATCH] VT-d: should not disable VT-d when find
> > unknown DMAR structure type
> >
> > Now 4 DMAR structure types are supported (type value 0 ~ 3). Type
> > values > 3 are reserved for future use. Current implementation disables
> > VT-d when find unknown DMAR structure type, this may lead to VT-d
> > disabling on future platforms before supporting new types on Xen. For
> > forward compatibility, just skip unknown structures by skipping the
> > appropriate number of bytes indicated by the Length field, and then VT-
> > d still can be used.
> >
> > Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>
> >
> > diff -r 298794763a75 xen/drivers/passthrough/vtd/dmar.c
> > --- a/xen/drivers/passthrough/vtd/dmar.c        Fri Mar 26 02:04:06 2010
> > +0800
> > +++ b/xen/drivers/passthrough/vtd/dmar.c        Fri Mar 26 02:08:45 2010
> > +0800
> > @@ -730,7 +730,6 @@ static int __init acpi_parse_dmar(struct
> >              dprintk(XENLOG_WARNING VTDPREFIX,
> >                      "Unknown DMAR structure type %x\n",
> >                      entry_header->type);
> > -            ret = -EINVAL;
> >              break;
> >          }
> >          if ( ret )
> >     
> Just a suggestion: Since this completely changes the meaning of the dprintk 
> message, the message should state that the unknown DMAR is being ignored. 
> Otherwise an end user might think that it means some kind of serious problem.
>
> Ed
>   
Good suggestion. Changed the warning message as below.

Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>

diff -r 18f4db5f72d7 xen/drivers/passthrough/vtd/dmar.c
--- a/xen/drivers/passthrough/vtd/dmar.c    Thu Mar 25 10:01:05 2010 +0000
+++ b/xen/drivers/passthrough/vtd/dmar.c    Fri Mar 26 10:12:32 2010 +0800
@@ -711,7 +711,7 @@ static int __init acpi_parse_dmar(struct
            break;
        default:
            dprintk(XENLOG_WARNING VTDPREFIX,
-                    "Unknown DMAR structure type %x\n",
+                    "Ignore unknown DMAR structure type (0x%x)\n",
                    entry_header->type);
            break;
        }


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