RE: [PATCH v10 5/7] vtd: use a bit field for root_entry

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

> From: Paul Durrant <paul@xen.org>
> Sent: Friday, November 20, 2020 9:25 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.
> 
> Also take the opportunity to tidy up the implementation of
> device_in_domain().
> 
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>

Reviewed-by: <kevin.tian@intel.com>

> ---
> Cc: Kevin Tian <kevin.tian@intel.com>
> 
> v10:
>  - Small tweaks requested by Jan
>  - Remove macros in favour of direct field access
>  - Add missing barrier
> 
> v4:
>  - New in v4
> ---
>  xen/drivers/passthrough/vtd/iommu.c   |  9 +++++----
>  xen/drivers/passthrough/vtd/iommu.h   | 25 ++++++++++++-------------
>  xen/drivers/passthrough/vtd/utils.c   |  6 +++---
>  xen/drivers/passthrough/vtd/x86/ats.c | 27 +++++++++++++++------------
>  4 files changed, 35 insertions(+), 32 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/vtd/iommu.c
> b/xen/drivers/passthrough/vtd/iommu.c
> index d136fe36883b..1a038541f0a3 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -237,7 +237,7 @@ static u64 bus_to_context_maddr(struct vtd_iommu
> *iommu, u8 bus)
>      ASSERT(spin_is_locked(&iommu->lock));
>      root_entries = (struct root_entry *)map_vtd_domain_page(iommu-
> >root_maddr);
>      root = &root_entries[bus];
> -    if ( !root_present(*root) )
> +    if ( !root->p )
>      {
>          maddr = alloc_pgtable_maddr(1, iommu->node);
>          if ( maddr == 0 )
> @@ -245,11 +245,12 @@ 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_present(*root);
> +        root->ctp = paddr_to_pfn(maddr);
> +        smp_wmb();
> +        root->p = true;
>          iommu_sync_cache(root, sizeof(struct root_entry));
>      }
> -    maddr = (u64) get_context_addr(*root);
> +    maddr = pfn_to_paddr(root->ctp);
>      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 216791b3d634..b14628eec260 100644
> --- a/xen/drivers/passthrough/vtd/iommu.h
> +++ b/xen/drivers/passthrough/vtd/iommu.h
> @@ -184,21 +184,20 @@
>  #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 {
> +        struct { uint64_t lo, hi; };
> +        struct {
> +            /* 0 - 63 */
> +            bool p:1;
> +            unsigned int 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)
> 
>  struct context_entry {
>      u64 lo;
> diff --git a/xen/drivers/passthrough/vtd/utils.c
> b/xen/drivers/passthrough/vtd/utils.c
> index 4febcf506d8a..5f25a86a535c 100644
> --- a/xen/drivers/passthrough/vtd/utils.c
> +++ b/xen/drivers/passthrough/vtd/utils.c
> @@ -112,15 +112,15 @@ 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);
> -    if ( !root_present(root_entry[bus]) )
> +    printk("    root_entry[%02x] = %"PRIx64"\n", bus, root_entry[bus].lo);
> +    if ( !root_entry[bus].p )
>      {
>          unmap_vtd_domain_page(root_entry);
>          printk("    root_entry[%02x] not present\n", bus);
>          return;
>      }
> 
> -    val = root_entry[bus].val;
> +    val = pfn_to_paddr(root_entry[bus].ctp);
>      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 04d702b1d6b1..fec969ef75bb 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;
> +    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_entry->p )
>          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_entry->ctp);
> +    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