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

[Peter Xu <peterx@redhat.com>]

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,

-- 
Peter Xu