Re: [PATCH RFCv2 6/8] backends/iommufd: Add ability to disable hugepages

[Avihai Horon <avihaih@nvidia.com>]

Hi Joao,

On 12/02/2024 15:56, Joao Martins wrote:
> External email: Use caution opening links or attachments
>
>
> Allow disabling hugepages to be dirty track at base page
> granularity in similar vein to vfio_type1_iommu.disable_hugepages
> but per IOAS.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
>   backends/iommufd.c       | 36 ++++++++++++++++++++++++++++++++++++
>   backends/trace-events    |  1 +
>   hw/vfio/iommufd.c        |  4 ++++
>   include/sysemu/iommufd.h |  4 ++++
>   qapi/qom.json            |  2 +-
>   5 files changed, 46 insertions(+), 1 deletion(-)
>
> diff --git a/backends/iommufd.c b/backends/iommufd.c
> index dd676d493c37..72fd98a9a50c 100644
> --- a/backends/iommufd.c
> +++ b/backends/iommufd.c
> @@ -29,6 +29,7 @@ static void iommufd_backend_init(Object *obj)
>       be->fd = -1;
>       be->users = 0;
>       be->owned = true;
> +    be->hugepages = 1;
>   }
>
>   static void iommufd_backend_finalize(Object *obj)
> @@ -63,6 +64,14 @@ static bool iommufd_backend_can_be_deleted(UserCreatable *uc)
>       return !be->users;
>   }
>
> +static void iommufd_backend_set_hugepages(Object *obj, bool enabled,
> +                                          Error **errp)
> +{
> +    IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
> +
> +    be->hugepages = enabled;
> +}
> +
>   static void iommufd_backend_class_init(ObjectClass *oc, void *data)
>   {
>       UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
> @@ -70,6 +79,11 @@ static void iommufd_backend_class_init(ObjectClass *oc, void *data)
>       ucc->can_be_deleted = iommufd_backend_can_be_deleted;
>
>       object_class_property_add_str(oc, "fd", NULL, iommufd_backend_set_fd);
> +
> +    object_class_property_add_bool(oc, "hugepages", NULL,
> +                                   iommufd_backend_set_hugepages);
> +    object_class_property_set_description(oc, "hugepages",
> +                                          "Set to 'off' to disable hugepages");
>   }
>
>   int iommufd_backend_connect(IOMMUFDBackend *be, Error **errp)
> @@ -106,6 +120,28 @@ out:
>       trace_iommufd_backend_disconnect(be->fd, be->users);
>   }
>
> +int iommufd_backend_set_option(int fd, uint32_t object_id,
> +                               uint32_t option_id, uint64_t val64)
> +{
> +    int ret;
> +    struct iommu_option option = {
> +        .size = sizeof(option),
> +        .option_id = option_id,
> +        .op = IOMMU_OPTION_OP_SET,
> +        .val64 = val64,
> +        .object_id = object_id,
> +    };
> +
> +    ret = ioctl(fd, IOMMU_OPTION, &option);
> +    if (ret) {
> +        error_report("Failed to set option %x to value %"PRIx64" %m", option_id,
> +                     val64);
> +    }
> +    trace_iommufd_backend_set_option(fd, object_id, option_id, val64, ret);
> +
> +    return ret;
> +}
> +
>   int iommufd_backend_alloc_ioas(IOMMUFDBackend *be, uint32_t *ioas_id,
>                                  Error **errp)
>   {
> diff --git a/backends/trace-events b/backends/trace-events
> index 11a27cb114b6..076166552881 100644
> --- a/backends/trace-events
> +++ b/backends/trace-events
> @@ -15,6 +15,7 @@ iommufd_backend_unmap_dma_non_exist(int iommufd, uint32_t ioas, uint64_t iova, u
>   iommufd_backend_unmap_dma(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size, int ret) " iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" (%d)"
>   iommufd_backend_alloc_hwpt(int iommufd, uint32_t dev_id, uint32_t pt_id, uint32_t flags, uint32_t hwpt_type, uint32_t len, uint64_t data_ptr, uint32_t out_hwpt_id, int ret) " iommufd=%d dev_id=%u pt_id=%u flags=0x%x hwpt_type=%u len=%u data_ptr=0x%"PRIx64" out_hwpt=%u (%d)"
>   iommufd_backend_alloc_ioas(int iommufd, uint32_t ioas, int ret) " iommufd=%d ioas=%d (%d)"
> +iommufd_backend_set_option(int iommufd, uint32_t object_id, uint32_t option_id, uint64_t val, int ret) " iommufd=%d object_id=%u option_id=%u val64=0x%"PRIx64" (%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)"
> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
> index 79b13bd262cc..697d40841d7f 100644
> --- a/hw/vfio/iommufd.c
> +++ b/hw/vfio/iommufd.c
> @@ -521,6 +521,10 @@ static int iommufd_cdev_attach(const char *name, VFIODevice *vbasedev,
>           goto err_alloc_ioas;
>       }
>
> +    if (!vbasedev->iommufd_dev.iommufd->hugepages) {
> +        iommufd_backend_set_option(vbasedev->iommufd_dev.iommufd->fd, ioas_id,
> +                                   IOMMU_OPTION_HUGE_PAGES, 0);

Shouldn't we fail device attach if iommufd_backend_set_option() fails?

Thanks.

> +    }
>       trace_iommufd_cdev_alloc_ioas(vbasedev->iommufd_dev.iommufd->fd, ioas_id);
>
>       container = g_malloc0(sizeof(*container));
> diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
> index ba19b7ea4c19..bc6607e3d444 100644
> --- a/include/sysemu/iommufd.h
> +++ b/include/sysemu/iommufd.h
> @@ -19,6 +19,7 @@ struct IOMMUFDBackend {
>       /*< protected >*/
>       int fd;            /* /dev/iommu file descriptor */
>       bool owned;        /* is the /dev/iommu opened internally */
> +    bool hugepages;    /* are hugepages enabled on the IOAS */
>       uint32_t users;
>
>       /*< public >*/
> @@ -30,6 +31,9 @@ void iommufd_backend_disconnect(IOMMUFDBackend *be);
>   int iommufd_backend_alloc_ioas(IOMMUFDBackend *be, uint32_t *ioas_id,
>                                  Error **errp);
>   void iommufd_backend_free_id(IOMMUFDBackend *be, uint32_t id);
> +int iommufd_backend_set_option(int fd, uint32_t object_id,
> +                               uint32_t option_id,
> +                               uint64_t val64);
>   int iommufd_backend_map_dma(IOMMUFDBackend *be, uint32_t ioas_id, hwaddr iova,
>                               ram_addr_t size, void *vaddr, bool readonly);
>   int iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
> diff --git a/qapi/qom.json b/qapi/qom.json
> index 84af23fe245d..9ad27e2b939b 100644
> --- a/qapi/qom.json
> +++ b/qapi/qom.json
> @@ -809,7 +809,7 @@
>   # Since: 9.0
>   ##
>   { 'struct': 'IOMMUFDProperties',
> -  'data': { '*fd': 'str' } }
> +  'data': { '*fd': 'str', '*hugepages': 'bool' } }
>
>   ##
>   # @RngProperties:
> --
> 2.39.3
>