Re: [PATCH RFCv2 5/8] vfio/iommufd: Implement VFIOIOMMUClass::query_dirty_bitmap support

[Joao Martins <joao.m.martins@oracle.com>]

On 19/02/2024 09:30, Avihai Horon wrote:
> Hi Joao,
> 
> On 12/02/2024 15:56, Joao Martins wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> ioctl(iommufd, IOMMU_HWPT_GET_DIRTY_BITMAP, arg) is the UAPI
>> that fetches the bitmap that tells what was dirty in an IOVA
>> range.
>>
>> A single bitmap is allocated and used across all the hwpts
>> sharing an IOAS which is then used in log_sync() to set Qemu
>> global bitmaps.
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>   backends/iommufd.c       | 24 ++++++++++++++++++++++++
>>   backends/trace-events    |  1 +
>>   hw/vfio/iommufd.c        | 30 ++++++++++++++++++++++++++++++
>>   include/sysemu/iommufd.h |  3 +++
>>   4 files changed, 58 insertions(+)
>>
>> diff --git a/backends/iommufd.c b/backends/iommufd.c
>> index 954de61c2da0..dd676d493c37 100644
>> --- a/backends/iommufd.c
>> +++ b/backends/iommufd.c
>> @@ -259,6 +259,30 @@ int iommufd_backend_set_dirty_tracking(IOMMUFDBackend
>> *be, uint32_t hwpt_id,
>>       return !ret ? 0 : -errno;
>>   }
>>
>> +int iommufd_backend_get_dirty_bitmap(IOMMUFDBackend *be, uint32_t hwpt_id,
>> +                                     uint64_t iova, ram_addr_t size,
>> +                                     uint64_t page_size, uint64_t *data)
>> +{
>> +    int ret;
>> +    struct iommu_hwpt_get_dirty_bitmap get_dirty_bitmap = {
>> +        .size = sizeof(get_dirty_bitmap),
>> +        .hwpt_id = hwpt_id,
>> +        .iova = iova, .length = size,
>> +        .page_size = page_size, .data = (uintptr_t)data,
> 
> Member per line for readability?
> 

Yeap

>> +    };
>> +
>> +    ret = ioctl(be->fd, IOMMU_HWPT_GET_DIRTY_BITMAP, &get_dirty_bitmap);
>> +    trace_iommufd_backend_get_dirty_bitmap(be->fd, hwpt_id, iova, size,
>> +                                           page_size, ret);
>> +    if (ret) {
>> +        error_report("IOMMU_HWPT_GET_DIRTY_BITMAP (iova: 0x%"PRIx64
>> +                     " size: 0x%"PRIx64") failed: %s", iova,
>> +                     size, strerror(errno));
>> +    }
>> +
>> +    return !ret ? 0 : -errno;
>> +}
>> +
>>   static const TypeInfo iommufd_backend_info = {
>>       .name = TYPE_IOMMUFD_BACKEND,
>>       .parent = TYPE_OBJECT,
>> diff --git a/backends/trace-events b/backends/trace-events
>> index feba2baca5f7..11a27cb114b6 100644
>> --- a/backends/trace-events
>> +++ b/backends/trace-events
>> @@ -17,3 +17,4 @@ iommufd_backend_alloc_hwpt(int iommufd, uint32_t dev_id,
>> uint32_t pt_id, uint32_
>>   iommufd_backend_alloc_ioas(int iommufd, uint32_t ioas, int ret) " iommufd=%d
>> ioas=%d (%d)"
>>   iommufd_backend_free_id(int iommufd, uint32_t id, int ret) " iommufd=%d
>> id=%d (%d)"
>>   iommufd_backend_set_dirty(int iommufd, uint32_t hwpt_id, bool start, int
>> ret) " iommufd=%d hwpt=%d enable=%d (%d)"
>> +iommufd_backend_get_dirty_bitmap(int iommufd, uint32_t hwpt_id, uint64_t
>> iova, uint64_t size, uint64_t page_size, int ret) " iommufd=%d hwpt=%d
>> iova=0x%"PRIx64" size=0x%"PRIx64" page_size=0x%"PRIx64" (%d)"
> 
> s/hwpt=%d/hwpt=%u
> 
/me nods

>> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>> index 361e659288fd..79b13bd262cc 100644
>> --- a/hw/vfio/iommufd.c
>> +++ b/hw/vfio/iommufd.c
>> @@ -25,6 +25,7 @@
>>   #include "qemu/cutils.h"
>>   #include "qemu/chardev_open.h"
>>   #include "pci.h"
>> +#include "exec/ram_addr.h"
>>   #include "migration/migration.h"
>>
>>   static int iommufd_cdev_map(const VFIOContainerBase *bcontainer, hwaddr iova,
>> @@ -142,6 +143,34 @@ err:
>>       return ret;
>>   }
>>
>> +static int iommufd_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
>> +                                      VFIOBitmap *vbmap, uint64_t iova,
>> +                                      uint64_t size)
>> +{
>> +    VFIOIOMMUFDContainer *container = container_of(bcontainer,
>> +                                                   VFIOIOMMUFDContainer,
>> +                                                   bcontainer);
>> +    int ret;
>> +    VFIOIOASHwpt *hwpt;
>> +    unsigned long page_size;
>> +
>> +    if (!bcontainer->dirty_pages_supported) {
> 
> Do we need this check?
> IIUC, if we got to iommufd_query_dirty_bitmap(), it means
> bcontainer->dirty_pages_supported is already true.
> 

Not quite. Look again at vfio_get_dirty_bitmap(); furthermore
vfio_container_query_dirty_bitmap() doesn't check for dirty_pages_supported.

I guess this check should be better placed into container-base class rather than
here.

> Thanks.
> 
>> +        return 0;
>> +    }
>> +
>> +    page_size = qemu_real_host_page_size();
>> +    QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
>> +        ret = iommufd_backend_get_dirty_bitmap(container->be, hwpt->hwpt_id,
>> +                                               iova, size, page_size,
>> +                                               vbmap->bitmap);
>> +        if (ret) {
>> +            break;
>> +        }
>> +    }
>> +
>> +    return ret;
>> +}
>> +
>>   static int iommufd_cdev_getfd(const char *sysfs_path, Error **errp)
>>   {
>>       long int ret = -ENOTTY;
>> @@ -765,6 +794,7 @@ static void vfio_iommu_iommufd_class_init(ObjectClass
>> *klass, void *data)
>>       vioc->pci_hot_reset = iommufd_cdev_pci_hot_reset;
>>       vioc->host_iommu_device_init = vfio_cdev_host_iommu_device_init;
>>       vioc->set_dirty_page_tracking = iommufd_set_dirty_page_tracking;
>> +    vioc->query_dirty_bitmap = iommufd_query_dirty_bitmap;
>>   };
>>
>>   static const TypeInfo types[] = {
>> diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
>> index 562c189dd92c..ba19b7ea4c19 100644
>> --- a/include/sysemu/iommufd.h
>> +++ b/include/sysemu/iommufd.h
>> @@ -55,5 +55,8 @@ int iommufd_backend_alloc_hwpt(int iommufd, uint32_t dev_id,
>>                                  void *data_ptr, uint32_t *out_hwpt);
>>   int iommufd_backend_set_dirty_tracking(IOMMUFDBackend *be, uint32_t hwpt_id,
>>                                          bool start);
>> +int iommufd_backend_get_dirty_bitmap(IOMMUFDBackend *be, uint32_t hwpt_id,
>> +                                     uint64_t iova, ram_addr_t size,
>> +                                     uint64_t page_size, uint64_t *data);
>>
>>   #endif
>> -- 
>> 2.39.3
>>