Re: [PATCH 1/6] x86/iommu: re-arrange arch_iommu to separate common fields...

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 24/07/2020 17:46, Paul Durrant wrote:
> diff --git a/xen/include/asm-x86/iommu.h b/xen/include/asm-x86/iommu.h
> index 6c9d5e5632..a7add5208c 100644
> --- a/xen/include/asm-x86/iommu.h
> +++ b/xen/include/asm-x86/iommu.h
> @@ -45,16 +45,23 @@ typedef uint64_t daddr_t;
>  
>  struct arch_iommu
>  {
> -    u64 pgd_maddr;                 /* io page directory machine address */
> -    spinlock_t mapping_lock;            /* io page table lock */
> -    int agaw;     /* adjusted guest address width, 0 is level 2 30-bit */
> -    u64 iommu_bitmap;              /* bitmap of iommu(s) that the domain 
> uses */
> -    struct list_head mapped_rmrrs;
> -
> -    /* amd iommu support */
> -    int paging_mode;
> -    struct page_info *root_table;
> -    struct guest_iommu *g_iommu;
> +    spinlock_t mapping_lock; /* io page table lock */
> +
> +    union {
> +        /* Intel VT-d */
> +        struct {
> +            u64 pgd_maddr; /* io page directory machine address */
> +            int agaw; /* adjusted guest address width, 0 is level 2 30-bit */
> +            u64 iommu_bitmap; /* bitmap of iommu(s) that the domain uses */
> +            struct list_head mapped_rmrrs;
> +        } vtd;
> +        /* AMD IOMMU */
> +        struct {
> +            int paging_mode;
> +            struct page_info *root_table;
> +            struct guest_iommu *g_iommu;
> +        } amd_iommu;
> +    };

The naming split here is weird.

Ideally we'd have struct {vtd,amd}_iommu in appropriate headers, and
this would be simply

union {
    struct vtd_iommu vtd;
    struct amd_iommu amd;
};

If this isn't trivial to arrange, can we at least s/amd_iommu/amd/ here ?

~Andrew