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

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 07/16/2015 04:26 AM, Alex Williamson wrote:
> 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.


Well, returning zero is better? Or qemu_real_host_page_size?



-- 
Alexey