Re: [PATCH V3 29/42] backends/iommufd: change process ioctl

[Steven Sistare <steven.sistare@oracle.com>]

On 5/16/2025 4:42 AM, Duan, Zhenzhong wrote:
>> -----Original Message-----
>> From: Steve Sistare <steven.sistare@oracle.com>
>> Subject: [PATCH V3 29/42] backends/iommufd: change process ioctl
>>
>> Define the change process ioctl
>>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> ---
>> backends/iommufd.c       | 20 ++++++++++++++++++++
>> backends/trace-events    |  1 +
>> include/system/iommufd.h |  2 ++
>> 3 files changed, 23 insertions(+)
>>
>> diff --git a/backends/iommufd.c b/backends/iommufd.c
>> index 5c1958f..6fed1c1 100644
>> --- a/backends/iommufd.c
>> +++ b/backends/iommufd.c
>> @@ -73,6 +73,26 @@ static void iommufd_backend_class_init(ObjectClass *oc,
>> const void *data)
>>      object_class_property_add_str(oc, "fd", NULL, iommufd_backend_set_fd);
>> }
>>
>> +bool iommufd_change_process_capable(IOMMUFDBackend *be)
>> +{
>> +    struct iommu_ioas_change_process args = {.size = sizeof(args)};
>> +
>> +    return !ioctl(be->fd, IOMMU_IOAS_CHANGE_PROCESS, &args);
>> +}
>> +
>> +bool iommufd_change_process(IOMMUFDBackend *be, Error **errp)
>> +{
>> +    struct iommu_ioas_change_process args = {.size = sizeof(args)};
>> +    bool ret = !ioctl(be->fd, IOMMU_IOAS_CHANGE_PROCESS, &args);
> 
> This is same ioctl as above check, could it be called more than once for same process?

Yes, and it is a no-op if the process has not changed since the last time DMA
was mapped.

- Steve

>> +
>> +    if (!ret) {
>> +        error_setg_errno(errp, errno, "IOMMU_IOAS_CHANGE_PROCESS fd %d
>> failed",
>> +                         be->fd);
>> +    }
>> +    trace_iommufd_change_process(be->fd, ret);
>> +    return ret;
>> +}
>> +
>> bool iommufd_backend_connect(IOMMUFDBackend *be, Error **errp)
>> {
>>      int fd;
>> diff --git a/backends/trace-events b/backends/trace-events
>> index f478e18..5ccdf90 100644
>> --- a/backends/trace-events
>> +++ b/backends/trace-events
>> @@ -7,6 +7,7 @@ dbus_vmstate_loading(const char *id) "id: %s"
>> dbus_vmstate_saving(const char *id) "id: %s"
>>
>> # iommufd.c
>> +iommufd_change_process(int fd, bool ret) "fd=%d (%d)"
>> iommufd_backend_connect(int fd, bool owned, uint32_t users) "fd=%d
>> owned=%d users=%d"
>> iommufd_backend_disconnect(int fd, uint32_t users) "fd=%d users=%d"
>> iommu_backend_set_fd(int fd) "pre-opened /dev/iommu fd=%d"
>> diff --git a/include/system/iommufd.h b/include/system/iommufd.h
>> index ac700b8..db9ed53 100644
>> --- a/include/system/iommufd.h
>> +++ b/include/system/iommufd.h
>> @@ -64,6 +64,8 @@ bool
>> 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,
>>                                        Error **errp);
>> +bool iommufd_change_process_capable(IOMMUFDBackend *be);
>> +bool iommufd_change_process(IOMMUFDBackend *be, Error **errp);
>>
>> #define TYPE_HOST_IOMMU_DEVICE_IOMMUFD TYPE_HOST_IOMMU_DEVICE
>> "-iommufd"
>> #endif
>> --
>> 1.8.3.1
>