Re: [PATCH v3 07/10] vfio/iommufd: Implement VFIOIOMMUClass::query_dirty_bitmap support

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

On 09/07/2024 08:05, Cédric Le Goater wrote:
> On 7/8/24 4:34 PM, Joao Martins wrote:
>> 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>
>> ---
>>   include/sysemu/iommufd.h |  3 +++
>>   backends/iommufd.c       | 26 ++++++++++++++++++++++++++
>>   hw/vfio/iommufd.c        | 34 ++++++++++++++++++++++++++++++++++
>>   backends/trace-events    |  1 +
>>   4 files changed, 64 insertions(+)
>>
>> diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
>> index 1470377f55ba..223f1ea14e84 100644
>> --- a/include/sysemu/iommufd.h
>> +++ b/include/sysemu/iommufd.h
>> @@ -56,6 +56,9 @@ int iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, 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);
>>     #define TYPE_HOST_IOMMU_DEVICE_IOMMUFD TYPE_HOST_IOMMU_DEVICE "-iommufd"
>>   diff --git a/backends/iommufd.c b/backends/iommufd.c
>> index 69daabc27473..b2d3bbd7c31b 100644
>> --- a/backends/iommufd.c
>> +++ b/backends/iommufd.c
>> @@ -257,6 +257,32 @@ int iommufd_backend_set_dirty_tracking(IOMMUFDBackend
>> *be, uint32_t hwpt_id,
>>       return ret;
>>   }
>>   +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,
>> +    };
>> +
>> +    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;
>> +}
>> +
>>   bool iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t devid,
>>                                        uint32_t *type, void *data, uint32_t len,
>>                                        uint64_t *caps, Error **errp)
>> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>> index 158a98cb3b12..9fad47baed9e 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"
>>     static int iommufd_cdev_map(const VFIOContainerBase *bcontainer, hwaddr iova,
>>                               ram_addr_t size, void *vaddr, bool readonly)
>> @@ -152,6 +153,38 @@ err:
>>       return ret;
>>   }
>>   +static int iommufd_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
>> +                                      VFIOBitmap *vbmap, hwaddr iova,
>> +                                      hwaddr size, Error **errp)
>> +{
>> +    VFIOIOMMUFDContainer *container = container_of(bcontainer,
>> +                                                   VFIOIOMMUFDContainer,
>> +                                                   bcontainer);
>> +    int ret;
>> +    VFIOIOASHwpt *hwpt;
>> +    unsigned long page_size;
>> +
>> +    page_size = qemu_real_host_page_size();
>> +    QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
>> +        if (!iommufd_hwpt_dirty_tracking(hwpt)) {
>> +            continue;
>> +        }
>> +
>> +        ret = iommufd_backend_get_dirty_bitmap(container->be, hwpt->hwpt_id,
>> +                                               iova, size, page_size,
>> +                                               vbmap->bitmap);
>> +        if (ret) {
>> +            error_setg_errno(errp, ret,
>> +                             "Failed to get dirty bitmap report, hwpt_id %u,
>> iova: "
>> +                             "0x%" HWADDR_PRIx ", size: 0x%" HWADDR_PRIx,
>> +                             hwpt->hwpt_id, iova, size);
> 
> This error looks redundant with the one printed out in
> iommufd_backend_get_dirty_bitmap(). Couldn't we add an 'Error **'
> parameter and simply return a bool ?
> 

I'll add it.

Just as a sidebar: This is a odd pattern which seems somewhat spread, that
somehow we only care about @errno as something to put on a message, rather then
letting the user know what exact error code it had returned programmatically.
Here in this series it is only important for the device attach so likely doesn't
justify a Error structure enhancement, hence the rest of functions I introduced
here can just adopt bool+errp.