Re: [Qemu-devel] [RFC PATCH qemu v3 1/4] memory: Add reporting of supported page sizes

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 2015-07-14 at 22:21 +1000, Alexey Kardashevskiy wrote:
> Every IOMMU has some granularity which MemoryRegionIOMMUOps::translate
> uses when translating, however this information is not available outside
> the translate context for various checks.
> 
> This adds a get_page_sizes callback to MemoryRegionIOMMUOps and
> a wrapper for it so IOMMU users (such as VFIO) can know the actual
> page size(s) used by an IOMMU.
> 
> TARGET_PAGE_BITS shift is used as fallback.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>  hw/ppc/spapr_iommu.c  |  8 ++++++++
>  include/exec/memory.h | 11 +++++++++++
>  memory.c              |  9 +++++++++
>  3 files changed, 28 insertions(+)
> 
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index f61504e..a2572c4 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -104,6 +104,13 @@ static IOMMUTLBEntry spapr_tce_translate_iommu(MemoryRegion *iommu, hwaddr addr,
>      return ret;
>  }
>  
> +static uint64_t spapr_tce_get_page_sizes(MemoryRegion *iommu)
> +{
> +    sPAPRTCETable *tcet = container_of(iommu, sPAPRTCETable, iommu);
> +
> +    return 1ULL << tcet->page_shift;
> +}
> +
>  static int spapr_tce_table_post_load(void *opaque, int version_id)
>  {
>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(opaque);
> @@ -135,6 +142,7 @@ static const VMStateDescription vmstate_spapr_tce_table = {
>  
>  static MemoryRegionIOMMUOps spapr_iommu_ops = {
>      .translate = spapr_tce_translate_iommu,
> +    .get_page_sizes = spapr_tce_get_page_sizes,
>  };
>  
>  static int spapr_tce_table_realize(DeviceState *dev)
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 1394715..9ca74e3 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -152,6 +152,8 @@ typedef struct MemoryRegionIOMMUOps MemoryRegionIOMMUOps;
>  struct MemoryRegionIOMMUOps {
>      /* Return a TLB entry that contains a given address. */
>      IOMMUTLBEntry (*translate)(MemoryRegion *iommu, hwaddr addr, bool is_write);
> +    /* Returns supported page sizes */
> +    uint64_t (*get_page_sizes)(MemoryRegion *iommu);
>  };
>  
>  typedef struct CoalescedMemoryRange CoalescedMemoryRange;
> @@ -552,6 +554,15 @@ static inline bool memory_region_is_romd(MemoryRegion *mr)
>  bool memory_region_is_iommu(MemoryRegion *mr);
>  
>  /**
> + * memory_region_iommu_get_page_sizes: get supported page sizes in an iommu
> + *
> + * Returns %bitmap of supported page sizes for an iommu.
> + *
> + * @mr: the memory region being queried
> + */
> +uint64_t memory_region_iommu_get_page_sizes(MemoryRegion *mr);
> +
> +/**
>   * memory_region_notify_iommu: notify a change in an IOMMU translation entry.
>   *
>   * @mr: the memory region that was changed
> diff --git a/memory.c b/memory.c
> index 5a0cc66..0732763 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1413,6 +1413,15 @@ bool memory_region_is_iommu(MemoryRegion *mr)
>      return mr->iommu_ops;
>  }
>  
> +uint64_t memory_region_iommu_get_page_sizes(MemoryRegion *mr)
> +{
> +    assert(memory_region_is_iommu(mr));
> +    if (mr->iommu_ops && mr->iommu_ops->get_page_sizes) {
> +        return mr->iommu_ops->get_page_sizes(mr);
> +    }
> +    return 1ULL << TARGET_PAGE_BITS;

At this rate we're adding TARGET_PAGE_foo faster than Peter can remove
them.

> +}
> +
>  void memory_region_register_iommu_notifier(MemoryRegion *mr, Notifier *n)
>  {
>      notifier_list_add(&mr->iommu_notify, n);