Re: [Qemu-devel] [PATCH v6 1/3] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 09, 2016 at 03:28:02PM +0800, Jason Wang wrote:
> 
> 
> On 2016年11月08日 19:04, Aviv B.D wrote:
> > From: "Aviv Ben-David" <bd.aviv@gmail.com>
> > 
> > This capability asks the guest to invalidate cache before each map operation.
> > We can use this invalidation to trap map operations in the hypervisor.
> 
> Hi:
> 
> Like I've asked twice in the past, I want to know why don't you cache
> translation faults as what spec required (especially this is a guest visible
> behavior)?
> 
> Btw, please cc me on posting future versions.
> 
> Thanks

Caching isn't guest visible. Spec just says you *can* cache,
not that you must.

> > 
> > Signed-off-by: Aviv Ben-David <bd.aviv@gmail.com>
> > ---
> >   hw/i386/intel_iommu.c          | 5 +++++
> >   hw/i386/intel_iommu_internal.h | 1 +
> >   include/hw/i386/intel_iommu.h  | 2 ++
> >   3 files changed, 8 insertions(+)
> > 
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 1655a65..834887f 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -2017,6 +2017,7 @@ static Property vtd_properties[] = {
> >       DEFINE_PROP_ON_OFF_AUTO("eim", IntelIOMMUState, intr_eim,
> >                               ON_OFF_AUTO_AUTO),
> >       DEFINE_PROP_BOOL("x-buggy-eim", IntelIOMMUState, buggy_eim, false),
> > +    DEFINE_PROP_BOOL("cache-mode", IntelIOMMUState, cache_mode_enabled, FALSE),
> >       DEFINE_PROP_END_OF_LIST(),
> >   };
> > @@ -2391,6 +2392,10 @@ static void vtd_init(IntelIOMMUState *s)
> >           assert(s->intr_eim != ON_OFF_AUTO_AUTO);
> >       }
> > +    if (s->cache_mode_enabled) {
> > +        s->cap |= VTD_CAP_CM;
> > +    }
> > +
> >       vtd_reset_context_cache(s);
> >       vtd_reset_iotlb(s);
> > diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> > index 0829a50..35d9f3a 100644
> > --- a/hw/i386/intel_iommu_internal.h
> > +++ b/hw/i386/intel_iommu_internal.h
> > @@ -201,6 +201,7 @@
> >   #define VTD_CAP_MAMV                (VTD_MAMV << 48)
> >   #define VTD_CAP_PSI                 (1ULL << 39)
> >   #define VTD_CAP_SLLPS               ((1ULL << 34) | (1ULL << 35))
> > +#define VTD_CAP_CM                  (1ULL << 7)
> >   /* Supported Adjusted Guest Address Widths */
> >   #define VTD_CAP_SAGAW_SHIFT         8
> > diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> > index 1989c1e..42d293f 100644
> > --- a/include/hw/i386/intel_iommu.h
> > +++ b/include/hw/i386/intel_iommu.h
> > @@ -258,6 +258,8 @@ struct IntelIOMMUState {
> >       uint8_t womask[DMAR_REG_SIZE];  /* WO (write only - read returns 0) */
> >       uint32_t version;
> > +    bool cache_mode_enabled;        /* RO - is cap CM enabled? */
> > +
> >       dma_addr_t root;                /* Current root table pointer */
> >       bool root_extended;             /* Type of root table (extended or not) */
> >       bool dmar_enabled;              /* Set if DMA remapping is enabled */