> From: Peter Xu [mailto:pet...@redhat.com] > Sent: Friday, January 20, 2017 4:55 PM > > On Fri, Jan 20, 2017 at 08:32:06AM +0000, Tian, Kevin wrote: > > > From: Peter Xu [mailto:pet...@redhat.com] > > > Sent: Friday, January 13, 2017 11:06 AM > > > > > > From: Aviv Ben-David <bd.a...@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. > > > > > > Signed-off-by: Aviv Ben-David <bd.a...@gmail.com> > > > Signed-off-by: Peter Xu <pet...@redhat.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 ec62239..2868e37 100644 > > > --- a/hw/i386/intel_iommu.c > > > +++ b/hw/i386/intel_iommu.c > > > @@ -2107,6 +2107,7 @@ 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(), > > > }; > > > > > > @@ -2488,6 +2489,10 @@ static void vtd_init(IntelIOMMUState *s) > > > s->ecap |= VTD_ECAP_DT; > > > } > > > > > > + if (s->cache_mode_enabled) { > > > + s->cap |= VTD_CAP_CM; > > > + } > > > + > > > > I think some of my old comments are not answered: > > > > 1) Better to use caching_mode to follow spec > > Sure. > > > > > 2) Does it make sense to automatically set this flag if any VFIO device > > has been statically assigned when starting Qemu? > > I'm okay with both, considering that people using this flag will be > possibly advanced users. So I would like to hear others' opinion. > > > Also for hot-add > > device path, some check of caching mode is required. If not set, > > should we fail hot-add operation? I don't think we have such physical > > platform with some devices behind IOMMU while others not. > > Could you explain in what case will we fail a hot plug? >
user enables intel-iommu, but don't set caching mode. Then later user hot-add a PCI device to the VM. Guest will assume newly assigned device also behind the default vIOMMU, and thus needs to setup IOVA mappings, which is then broken... Thanks Kevin
