Re: [PATCH v5 07/15] iommu: track reserved ranges using a rangeset

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Paul Durrant [mailto:paul.durrant@citrix.com]
> Sent: Saturday, August 4, 2018 1:22 AM
> 
> Ranges that should be considered reserved in the IOMMU are not
> necessarily
> limited to RMRRs. If iommu_inclusive_mapping is set then any frame
> number
> falling within an E820 reserved region should also be considered as
> reserved in the IOMMU.

I don't think it is a good extension. RMRR by definition requires 
identity mapping in IOMMU page table, thus must be also reserved
in bfn address space (to avoid being used for other purpose). 
Normal E820 reserved regions have no such requirement. Guest
can use same bfn location for any purpose. I'm not sure why we
want to add more limitations here.

> This patch adds a rangeset to the domain_iommu structure that is then
> used
> to track all reserved ranges. This will be needed by a subsequent patch
> to test whether it is safe to modify a particular IOMMU entry.
> 
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> Reviewed-by: George Dunlap <george.dunlap@citrix.com>
> Reviewed-by: Wei Liu <wei.liu2@citrix.com>
> ---
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Kevin Tian <kevin.tian@intel.com>
> 
> v2:
>  - New in v2.
> ---
>  xen/drivers/passthrough/iommu.c       | 10 +++++++++-
>  xen/drivers/passthrough/vtd/iommu.c   | 20 +++++++++++++-------
>  xen/drivers/passthrough/vtd/x86/vtd.c | 17 ++++++++++++++++-
>  xen/include/xen/iommu.h               |  6 ++++++
>  4 files changed, 44 insertions(+), 9 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/iommu.c
> b/xen/drivers/passthrough/iommu.c
> index 21e6886a3f..b10a37e5d7 100644
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -147,6 +147,10 @@ int iommu_domain_init(struct domain *d)
>      if ( !iommu_enabled )
>          return 0;
> 
> +    hd->reserved_ranges = rangeset_new(d, NULL, 0);
> +    if ( !hd->reserved_ranges )
> +        return -ENOMEM;
> +
>      hd->platform_ops = iommu_get_ops();
>      return hd->platform_ops->init(d);
>  }
> @@ -248,12 +252,16 @@ int iommu_construct(struct domain *d)
> 
>  void iommu_domain_destroy(struct domain *d)
>  {
> -    if ( !iommu_enabled || !dom_iommu(d)->platform_ops )
> +    const struct domain_iommu *hd = dom_iommu(d);
> +
> +    if ( !iommu_enabled || !hd->platform_ops )
>          return;
> 
>      iommu_teardown(d);
> 
>      arch_iommu_domain_destroy(d);
> +
> +    rangeset_destroy(hd->reserved_ranges);
>  }
> 
>  int iommu_map_page(struct domain *d, bfn_t bfn, mfn_t mfn,
> diff --git a/xen/drivers/passthrough/vtd/iommu.c
> b/xen/drivers/passthrough/vtd/iommu.c
> index c9f50f04ad..282e227414 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -1910,6 +1910,7 @@ static int rmrr_identity_mapping(struct domain
> *d, bool_t map,
>      unsigned long end_pfn = PAGE_ALIGN_4K(rmrr->end_address) >>
> PAGE_SHIFT_4K;
>      struct mapped_rmrr *mrmrr;
>      struct domain_iommu *hd = dom_iommu(d);
> +    int err = 0;
> 
>      ASSERT(pcidevs_locked());
>      ASSERT(rmrr->base_address < rmrr->end_address);
> @@ -1923,8 +1924,6 @@ static int rmrr_identity_mapping(struct domain
> *d, bool_t map,
>          if ( mrmrr->base == rmrr->base_address &&
>               mrmrr->end == rmrr->end_address )
>          {
> -            int ret = 0;
> -
>              if ( map )
>              {
>                  ++mrmrr->count;
> @@ -1934,28 +1933,35 @@ static int rmrr_identity_mapping(struct
> domain *d, bool_t map,
>              if ( --mrmrr->count )
>                  return 0;
> 
> -            while ( base_pfn < end_pfn )
> +            err = rangeset_remove_range(hd->reserved_ranges,
> +                                        base_pfn, end_pfn);
> +            while ( !err && base_pfn < end_pfn )
>              {
>                  if ( clear_identity_p2m_entry(d, base_pfn) )
> -                    ret = -ENXIO;
> +                    err = -ENXIO;
> +
>                  base_pfn++;
>              }
> 
>              list_del(&mrmrr->list);
>              xfree(mrmrr);
> -            return ret;
> +            return err;
>          }
>      }
> 
>      if ( !map )
>          return -ENOENT;
> 
> +    err = rangeset_add_range(hd->reserved_ranges, base_pfn, end_pfn);
> +    if ( err )
> +        return err;
> +
>      while ( base_pfn < end_pfn )
>      {
> -        int err = set_identity_p2m_entry(d, base_pfn, p2m_access_rw, flag);
> -
> +        err = set_identity_p2m_entry(d, base_pfn, p2m_access_rw, flag);
>          if ( err )
>              return err;
> +
>          base_pfn++;
>      }
> 
> diff --git a/xen/drivers/passthrough/vtd/x86/vtd.c
> b/xen/drivers/passthrough/vtd/x86/vtd.c
> index 6fed4a92cb..032412b8c6 100644
> --- a/xen/drivers/passthrough/vtd/x86/vtd.c
> +++ b/xen/drivers/passthrough/vtd/x86/vtd.c
> @@ -164,10 +164,25 @@ void __hwdom_init
> vtd_set_hwdom_mapping(struct domain *d)
> 
>              if ( !rc )
>                 rc = ret;
> +
> +            /*
> +             * The only reason a reserved page would be mapped is that
> +             * iommu_inclusive_mapping is set, in which case the BFN
> +             * needs to be marked as reserved in the IOMMU.
> +             */
> +            if ( page_is_ram_type(pfn, RAM_TYPE_RESERVED) )
> +            {
> +                ASSERT(iommu_inclusive_mapping);
> +
> +                ret = rangeset_add_singleton(dom_iommu(d)->reserved_ranges,
> +                                             bfn_x(bfn));
> +                if ( !rc )
> +                    rc = ret;
> +            }
>          }
> 
>          if ( rc )
> -            printk(XENLOG_WARNING VTDPREFIX " d%d: IOMMU mapping
> failed: %d\n",
> +            printk(XENLOG_WARNING VTDPREFIX " d%d: IOMMU
> mapping/reservation failed: %d\n",
>                     d->domain_id, rc);
> 
>          if (!(i & (0xfffff >> (PAGE_SHIFT - PAGE_SHIFT_4K))))
> diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> index 624784fec8..cc0be81b4e 100644
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -122,6 +122,12 @@ struct domain_iommu {
> 
>      /* Features supported by the IOMMU */
>      DECLARE_BITMAP(features, IOMMU_FEAT_count);
> +
> +    /*
> +     * BFN ranges that are reserved in the domain IOMMU mappings and
> +     * must not be modified after initialization.
> +     */
> +    struct rangeset *reserved_ranges;
>  };
> 
>  #define dom_iommu(d)              (&(d)->iommu)
> --
> 2.11.0


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