Re: [Qemu-devel] [PATCH v3 1/2] intel_iommu: check validity for GAW bits in CE

[Michael S. Tsirkin]

On Wed, Dec 14, 2016 at 10:09:04AM +0800, Peter Xu wrote:
> Currently vt-d Context Entry (CE) only allows 39/48 bits address width.
> If guest software configured more than that, we complain and report.
> 
> Signed-off-by: Peter Xu <address@hidden>
> ---
>  hw/i386/intel_iommu.c          | 17 ++++++++++++++++-
>  hw/i386/intel_iommu_internal.h |  2 ++
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 5f3e351..517a2a3 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -599,9 +599,19 @@ static inline uint32_t 
> vtd_get_level_from_context_entry(VTDContextEntry *ce)
>      return 2 + (ce->hi & VTD_CONTEXT_ENTRY_AW);
>  }
>  
> +/* Return 0 if failed to fetch valid aw */
>  static inline uint32_t vtd_get_agaw_from_context_entry(VTDContextEntry *ce)
>  {
> -    return 30 + (ce->hi & VTD_CONTEXT_ENTRY_AW) * 9;
> +    uint8_t aw = (ce->hi & VTD_CONTEXT_ENTRY_AW);
> +    /*
> +     * According to vt-d spec 10.4.2 bits 12:8, SAGAW only allows
> +     * 39/48 bits.
> +     */
> +    if (aw > VTD_CE_AW_48BIT) {

5-level is almost sure to allow more. I don't see the point of this test.

> +        error_report("Context entry address width not supported (aw=%d)" , 
> aw);
> +        return 0;
> +    }
> +    return 30 + aw * 9;
>  }
>  
>  static const uint64_t vtd_paging_entry_rsvd_field[] = {
> @@ -642,6 +652,11 @@ static int vtd_gpa_to_slpte(VTDContextEntry *ce, 
> uint64_t gpa, bool is_write,
>      uint32_t ce_agaw = vtd_get_agaw_from_context_entry(ce);
>      uint64_t access_right_check;
>  
> +    if (!ce_agaw) {
> +        error_report("Illegal context entry AGAW");
> +        return -VTD_FR_CONTEXT_ENTRY_INV;
> +    }
> +
>      /* Check if @gpa is above 2^X-1, where X is the minimum of MGAW in 
> CAP_REG
>       * and AW in context-entry.
>       */
> diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> index 11abfa2..e808c67 100644
> --- a/hw/i386/intel_iommu_internal.h
> +++ b/hw/i386/intel_iommu_internal.h
> @@ -406,6 +406,8 @@ typedef struct VTDRootEntry VTDRootEntry;
>  #define VTD_CONTEXT_ENTRY_RSVD_LO   (0xff0ULL | ~VTD_HAW_MASK)
>  /* hi */
>  #define VTD_CONTEXT_ENTRY_AW        7ULL /* Adjusted guest-address-width */
> +#define VTD_CE_AW_39BIT             1
> +#define VTD_CE_AW_48BIT             2
>  #define VTD_CONTEXT_ENTRY_DID(val)  (((val) >> 8) & VTD_DOMAIN_ID_MASK)
>  #define VTD_CONTEXT_ENTRY_RSVD_HI   0xffffffffff000080ULL
>  
> -- 
> 2.7.4