Re: [PATCH v10 6/7] vtd: use a bit field for context_entry

[Jan Beulich <jbeulich@suse.com>]

On 20.11.2020 14:24, Paul Durrant wrote:
> @@ -121,21 +119,22 @@ static int context_set_domain_id(struct context_entry *context,
>      }
>  
>      set_bit(i, iommu->domid_bitmap);
> -    context->hi |= (i & ((1 << DID_FIELD_WIDTH) - 1)) << DID_HIGH_OFFSET;
> +    context->did = i;
> +
>      return 0;
>  }
>  
>  static int context_get_domain_id(struct context_entry *context,
>                                   struct vtd_iommu *iommu)
>  {
> -    unsigned long dom_index, nr_dom;
>      int domid = -1;
>  
>      if (iommu && context)
>      {
> -        nr_dom = cap_ndoms(iommu->cap);
> +        unsigned long dom_index, nr_dom;

unsigned int will do here.

> -        dom_index = context_domain_id(*context);
> +        nr_dom = cap_ndoms(iommu->cap);
> +        dom_index = context->did;

These could also become the initializers of the variables now.

> --- a/xen/drivers/passthrough/vtd/iommu.h
> +++ b/xen/drivers/passthrough/vtd/iommu.h
> @@ -198,37 +198,34 @@ struct root_entry {
>          };
>      };
>  };
> +#define ROOT_ENTRY_NR (PAGE_SIZE_4K / sizeof(struct root_entry))
>  
>  struct context_entry {
> -    u64 lo;
> -    u64 hi;
> -};
> -#define ROOT_ENTRY_NR (PAGE_SIZE_4K/sizeof(struct root_entry))
> -#define context_present(c) ((c).lo & 1)
> -#define context_fault_disable(c) (((c).lo >> 1) & 1)
> -#define context_translation_type(c) (((c).lo >> 2) & 3)
> -#define context_address_root(c) ((c).lo & PAGE_MASK_4K)
> -#define context_address_width(c) ((c).hi &  7)
> -#define context_domain_id(c) (((c).hi >> 8) & ((1 << 16) - 1))
> +    union {
> +        __uint128_t val;
> +        struct { uint64_t lo, hi; };
> +        struct {
> +            /* 0 - 63 */
> +            bool p:1;
> +            bool fpd:1;
> +            uint64_t tt:2;

unsigned int

With these taken care of
Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan