Re: [Qemu-devel] [RFC PATCH 02/20] intel_iommu: exposed extended-context mode to guest

["Liu, Yi L" <yi.l.liu@linux.intel.com>]

On Fri, Apr 28, 2017 at 02:00:15PM +0800, Lan Tianyu wrote:
> On 2017年04月27日 18:32, Peter Xu wrote:
> > On Wed, Apr 26, 2017 at 06:06:32PM +0800, Liu, Yi L wrote:
> >> VT-d implementations reporting PASID or PRS fields as "Set", must also
> >> report ecap.ECS as "Set". Extended-Context is required for SVM.
> >>
> >> When ECS is reported, intel iommu driver would initiate extended root entry
> >> and extended context entry, and also PASID table if there is any SVM capable
> >> device.
> >>
> >> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> >> ---
> >>  hw/i386/intel_iommu.c          | 131 +++++++++++++++++++++++++++--------------
> >>  hw/i386/intel_iommu_internal.h |   9 +++
> >>  include/hw/i386/intel_iommu.h  |   2 +-
> >>  3 files changed, 97 insertions(+), 45 deletions(-)
> >>
> >> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> >> index 400d0d1..bf98fa5 100644
> >> --- a/hw/i386/intel_iommu.c
> >> +++ b/hw/i386/intel_iommu.c
> >> @@ -497,6 +497,11 @@ static inline bool vtd_root_entry_present(VTDRootEntry *root)
> >>      return root->val & VTD_ROOT_ENTRY_P;
> >>  }
> >>  
> >> +static inline bool vtd_root_entry_upper_present(VTDRootEntry *root)
> >> +{
> >> +    return root->rsvd & VTD_ROOT_ENTRY_P;
> >> +}
> >> +
> >>  static int vtd_get_root_entry(IntelIOMMUState *s, uint8_t index,
> >>                                VTDRootEntry *re)
> >>  {
> >> @@ -509,6 +514,9 @@ static int vtd_get_root_entry(IntelIOMMUState *s, uint8_t index,
> >>          return -VTD_FR_ROOT_TABLE_INV;
> >>      }
> >>      re->val = le64_to_cpu(re->val);
> >> +    if (s->ecs) {
> >> +        re->rsvd = le64_to_cpu(re->rsvd);
> >> +    }
> > 
> > I feel it slightly hacky to play with re->rsvd. How about:
> > 
> > union VTDRootEntry {
> >     struct {
> >         uint64_t val;
> >         uint64_t rsvd;
> >     } base;
> >     struct {
> >         uint64_t ext_lo;
> >         uint64_t ext_hi;
> >     } extended;
> > };
> > 
> > (Or any better way that can get rid of rsvd...)
> > 
> > Even:
> > 
> > struct VTDRootEntry {
> >     union {
> >         struct {
> >                 uint64_t val;
> >                 uint64_t rsvd;
> >         } base;
> >         struct {
> >                 uint64_t ext_lo;
> >                 uint64_t ext_hi;
> >         } extended;
> >     } data;
> >     bool extended;
> > };
> > 
> > Then we read the entry into data, and setup extended bit. A benefit of
> > it is that we may avoid passing around IntelIOMMUState everywhere to
> > know whether we are using extended context entries.
> > 
> >>      return 0;
> >>  }
> >>  
> >> @@ -517,19 +525,30 @@ static inline bool vtd_context_entry_present(VTDContextEntry *context)
> >>      return context->lo & VTD_CONTEXT_ENTRY_P;
> >>  }
> >>  
> >> -static int vtd_get_context_entry_from_root(VTDRootEntry *root, uint8_t index,
> >> -                                           VTDContextEntry *ce)
> >> +static int vtd_get_context_entry_from_root(IntelIOMMUState *s,
> >> +                 VTDRootEntry *root, uint8_t index, VTDContextEntry *ce)
> >>  {
> >> -    dma_addr_t addr;
> >> +    dma_addr_t addr, ce_size;
> >>  
> >>      /* we have checked that root entry is present */
> >> -    addr = (root->val & VTD_ROOT_ENTRY_CTP) + index * sizeof(*ce);
> >> -    if (dma_memory_read(&address_space_memory, addr, ce, sizeof(*ce))) {
> >> +    ce_size = (s->ecs) ? (2 * sizeof(*ce)) : (sizeof(*ce));
> >> +    addr = (s->ecs && (index > 0x7f)) ?
> >> +           ((root->rsvd & VTD_ROOT_ENTRY_CTP) + (index - 0x80) * ce_size) :
> >> +           ((root->val & VTD_ROOT_ENTRY_CTP) + index * ce_size);
> >> +
> >> +    if (dma_memory_read(&address_space_memory, addr, ce, ce_size)) {
> >>          trace_vtd_re_invalid(root->rsvd, root->val);
> >>          return -VTD_FR_CONTEXT_TABLE_INV;
> >>      }
> >> -    ce->lo = le64_to_cpu(ce->lo);
> >> -    ce->hi = le64_to_cpu(ce->hi);
> >> +
> >> +    ce[0].lo = le64_to_cpu(ce[0].lo);
> >> +    ce[0].hi = le64_to_cpu(ce[0].hi);
> > 
> > Again, I feel this even hackier. :)
> > 
> > I would slightly prefer to play the same union trick to context
> > entries, just like what I proposed to the root entries above...
> > 
> >> +
> >> +    if (s->ecs) {
> >> +        ce[1].lo = le64_to_cpu(ce[1].lo);
> >> +        ce[1].hi = le64_to_cpu(ce[1].hi);
> >> +    }
> >> +
> >>      return 0;
> >>  }
> >>  
> >> @@ -595,9 +614,11 @@ static inline uint32_t vtd_get_agaw_from_context_entry(VTDContextEntry *ce)
> >>      return 30 + (ce->hi & VTD_CONTEXT_ENTRY_AW) * 9;
> >>  }
> >>  
> >> -static inline uint32_t vtd_ce_get_type(VTDContextEntry *ce)
> >> +static inline uint32_t vtd_ce_get_type(IntelIOMMUState *s,
> >> +                                       VTDContextEntry *ce)
> >>  {
> >> -    return ce->lo & VTD_CONTEXT_ENTRY_TT;
> >> +    return s->ecs ? (ce->lo & VTD_CONTEXT_ENTRY_TT) :
> >> +                    (ce->lo & VTD_EXT_CONTEXT_ENTRY_TT);
> >>  }
> >>  
> >>  static inline uint64_t vtd_iova_limit(VTDContextEntry *ce)
> >> @@ -842,16 +863,20 @@ static int vtd_dev_to_context_entry(IntelIOMMUState *s, uint8_t bus_num,
> >>          return ret_fr;
> >>      }
> >>  
> >> -    if (!vtd_root_entry_present(&re)) {
> >> +    if (!vtd_root_entry_present(&re) ||
> >> +        (s->ecs && (devfn > 0x7f) && (!vtd_root_entry_upper_present(&re)))) {
> >>          /* Not error - it's okay we don't have root entry. */
> >>          trace_vtd_re_not_present(bus_num);
> >>          return -VTD_FR_ROOT_ENTRY_P;
> >> -    } else if (re.rsvd || (re.val & VTD_ROOT_ENTRY_RSVD)) {
> >> -        trace_vtd_re_invalid(re.rsvd, re.val);
> >> -        return -VTD_FR_ROOT_ENTRY_RSVD;
> >> +    }
> >> +    if ((s->ecs && (devfn > 0x7f) && (re.rsvd & VTD_ROOT_ENTRY_RSVD)) ||
> >> +        (s->ecs && (devfn < 0x80) && (re.val & VTD_ROOT_ENTRY_RSVD)) ||
> >> +        ((!s->ecs) && (re.rsvd || (re.val & VTD_ROOT_ENTRY_RSVD)))) {
> >> +            trace_vtd_re_invalid(re.rsvd, re.val);
> >> +            return -VTD_FR_ROOT_ENTRY_RSVD;
> > 
> > Nit: I feel like we can better wrap these 0x7f and 0x80 into helper
> > functions, especially if with above structure change...
> > 
> > (will hold here...)
> > 
> > Thanks,
> > 
> 
> 
> It's possible to add helper macro to check bits in context entry and
> extend context entry and put the check of ecs mode into helper macro?

yes, would add accordingly in next version.