RE: [PATCH v4 12/14] vtd: use a bit field for root_entry

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

> From: Paul Durrant <paul@xen.org>
> Sent: Tuesday, August 4, 2020 9:42 PM
> 
> From: Paul Durrant <pdurrant@amazon.com>
> 
> This makes the code a little easier to read and also makes it more consistent
> with iremap_entry.

I feel the original readability is slightly better, as ctp is less obvious than
set_root_value, get_context_addr, etc.

Thanks
Kevin

> 
> Also take the opportunity to tidy up the implementation of
> device_in_domain().
> 
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> ---
> Cc: Kevin Tian <kevin.tian@intel.com>
> 
> v4:
>  - New in v4
> ---
>  xen/drivers/passthrough/vtd/iommu.c   |  4 ++--
>  xen/drivers/passthrough/vtd/iommu.h   | 33 ++++++++++++++++-----------
>  xen/drivers/passthrough/vtd/utils.c   |  4 ++--
>  xen/drivers/passthrough/vtd/x86/ats.c | 27 ++++++++++++----------
>  4 files changed, 39 insertions(+), 29 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/vtd/iommu.c
> b/xen/drivers/passthrough/vtd/iommu.c
> index f8da4fe0e7..76025f6ccd 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -245,11 +245,11 @@ static u64 bus_to_context_maddr(struct
> vtd_iommu *iommu, u8 bus)
>              unmap_vtd_domain_page(root_entries);
>              return 0;
>          }
> -        set_root_value(*root, maddr);
> +        set_root_ctp(*root, maddr);
>          set_root_present(*root);
>          iommu_sync_cache(root, sizeof(struct root_entry));
>      }
> -    maddr = (u64) get_context_addr(*root);
> +    maddr = root_ctp(*root);
>      unmap_vtd_domain_page(root_entries);
>      return maddr;
>  }
> diff --git a/xen/drivers/passthrough/vtd/iommu.h
> b/xen/drivers/passthrough/vtd/iommu.h
> index 216791b3d6..031ac5f66c 100644
> --- a/xen/drivers/passthrough/vtd/iommu.h
> +++ b/xen/drivers/passthrough/vtd/iommu.h
> @@ -184,21 +184,28 @@
>  #define dma_frcd_source_id(c) (c & 0xffff)
>  #define dma_frcd_page_addr(d) (d & (((u64)-1) << 12)) /* low 64 bit */
> 
> -/*
> - * 0: Present
> - * 1-11: Reserved
> - * 12-63: Context Ptr (12 - (haw-1))
> - * 64-127: Reserved
> - */
>  struct root_entry {
> -    u64    val;
> -    u64    rsvd1;
> +    union {
> +        __uint128_t val;
> +        struct { uint64_t lo, hi; };
> +        struct {
> +            /* 0 - 63 */
> +            uint64_t p:1;
> +            uint64_t reserved0:11;
> +            uint64_t ctp:52;
> +
> +            /* 64 - 127 */
> +            uint64_t reserved1;
> +        };
> +    };
>  };
> -#define root_present(root)    ((root).val & 1)
> -#define set_root_present(root) do {(root).val |= 1;} while(0)
> -#define get_context_addr(root) ((root).val & PAGE_MASK_4K)
> -#define set_root_value(root, value) \
> -    do {(root).val |= ((value) & PAGE_MASK_4K);} while(0)
> +
> +#define root_present(r) (r).p
> +#define set_root_present(r) do { (r).p = 1; } while (0)
> +
> +#define root_ctp(r) ((r).ctp << PAGE_SHIFT_4K)
> +#define set_root_ctp(r, val) \
> +    do { (r).ctp = ((val) >> PAGE_SHIFT_4K); } while (0)
> 
>  struct context_entry {
>      u64 lo;
> diff --git a/xen/drivers/passthrough/vtd/utils.c
> b/xen/drivers/passthrough/vtd/utils.c
> index 4febcf506d..4c85242894 100644
> --- a/xen/drivers/passthrough/vtd/utils.c
> +++ b/xen/drivers/passthrough/vtd/utils.c
> @@ -112,7 +112,7 @@ void print_vtd_entries(struct vtd_iommu *iommu, int
> bus, int devfn, u64 gmfn)
>          return;
>      }
> 
> -    printk("    root_entry[%02x] = %"PRIx64"\n", bus, root_entry[bus].val);
> +    printk("    root_entry[%02x] = %"PRIx64"\n", bus, root_entry[bus].lo);
>      if ( !root_present(root_entry[bus]) )
>      {
>          unmap_vtd_domain_page(root_entry);
> @@ -120,7 +120,7 @@ void print_vtd_entries(struct vtd_iommu *iommu, int
> bus, int devfn, u64 gmfn)
>          return;
>      }
> 
> -    val = root_entry[bus].val;
> +    val = root_ctp(root_entry[bus]);
>      unmap_vtd_domain_page(root_entry);
>      ctxt_entry = map_vtd_domain_page(val);
>      if ( ctxt_entry == NULL )
> diff --git a/xen/drivers/passthrough/vtd/x86/ats.c
> b/xen/drivers/passthrough/vtd/x86/ats.c
> index 04d702b1d6..8369415dcc 100644
> --- a/xen/drivers/passthrough/vtd/x86/ats.c
> +++ b/xen/drivers/passthrough/vtd/x86/ats.c
> @@ -74,8 +74,8 @@ int ats_device(const struct pci_dev *pdev, const struct
> acpi_drhd_unit *drhd)
>  static bool device_in_domain(const struct vtd_iommu *iommu,
>                               const struct pci_dev *pdev, uint16_t did)
>  {
> -    struct root_entry *root_entry;
> -    struct context_entry *ctxt_entry = NULL;
> +    struct root_entry *root_entry, *root_entries = NULL;
> +    struct context_entry *context_entry, *context_entries = NULL;
>      unsigned int tt;
>      bool found = false;
> 
> @@ -85,25 +85,28 @@ static bool device_in_domain(const struct
> vtd_iommu *iommu,
>          return false;
>      }
> 
> -    root_entry = map_vtd_domain_page(iommu->root_maddr);
> -    if ( !root_present(root_entry[pdev->bus]) )
> +    root_entries = (struct root_entry *)map_vtd_domain_page(iommu-
> >root_maddr);
> +    root_entry = &root_entries[pdev->bus];
> +    if ( !root_present(*root_entry) )
>          goto out;
> 
> -    ctxt_entry = map_vtd_domain_page(root_entry[pdev->bus].val);
> -    if ( context_domain_id(ctxt_entry[pdev->devfn]) != did )
> +    context_entries = map_vtd_domain_page(root_ctp(*root_entry));
> +    context_entry = &context_entries[pdev->devfn];
> +    if ( context_domain_id(*context_entry) != did )
>          goto out;
> 
> -    tt = context_translation_type(ctxt_entry[pdev->devfn]);
> +    tt = context_translation_type(*context_entry);
>      if ( tt != CONTEXT_TT_DEV_IOTLB )
>          goto out;
> 
>      found = true;
> -out:
> -    if ( root_entry )
> -        unmap_vtd_domain_page(root_entry);
> 
> -    if ( ctxt_entry )
> -        unmap_vtd_domain_page(ctxt_entry);
> + out:
> +    if ( root_entries )
> +        unmap_vtd_domain_page(root_entries);
> +
> +    if ( context_entries )
> +        unmap_vtd_domain_page(context_entries);
> 
>      return found;
>  }
> --
> 2.20.1