Re: [Qemu-devel] [PATCH 3/3] uuid: Make qemu_uuid_bswap() take and return a QemuUUID

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Dec 10, 2018 at 11:26:49AM +0000, Peter Maydell wrote:
> Currently qemu_uuid_bswap() takes a pointer to the QemuUUID to
> be byte-swapped. This means it can't be used when the UUID
> to be swapped is in a packed member of a struct. It's also
> out of line with the general bswap*() functions we provide
> in bswap.h, which take the value to be swapped and return it.
> 
> Make qemu_uuid_bswap() take a QemuUUID and return the swapped version.
> 
> This fixes some clang warnings about taking the address of
> a packed struct member in block/vdi.c.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

For acpi:

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  include/qemu/uuid.h  |  2 +-
>  block/vdi.c          | 16 ++++++++--------
>  hw/acpi/vmgenid.c    |  6 ++----
>  tests/vmgenid-test.c |  2 +-
>  util/uuid.c          | 10 +++++-----
>  5 files changed, 17 insertions(+), 19 deletions(-)
> 
> diff --git a/include/qemu/uuid.h b/include/qemu/uuid.h
> index 09489ce5c5e..037357d990b 100644
> --- a/include/qemu/uuid.h
> +++ b/include/qemu/uuid.h
> @@ -56,6 +56,6 @@ char *qemu_uuid_unparse_strdup(const QemuUUID *uuid);
>  
>  int qemu_uuid_parse(const char *str, QemuUUID *uuid);
>  
> -void qemu_uuid_bswap(QemuUUID *uuid);
> +QemuUUID qemu_uuid_bswap(QemuUUID uuid);
>  
>  #endif
> diff --git a/block/vdi.c b/block/vdi.c
> index 4cc726047c3..0c34f6bae46 100644
> --- a/block/vdi.c
> +++ b/block/vdi.c
> @@ -203,10 +203,10 @@ static void vdi_header_to_cpu(VdiHeader *header)
>      header->block_extra = le32_to_cpu(header->block_extra);
>      header->blocks_in_image = le32_to_cpu(header->blocks_in_image);
>      header->blocks_allocated = le32_to_cpu(header->blocks_allocated);
> -    qemu_uuid_bswap(&header->uuid_image);
> -    qemu_uuid_bswap(&header->uuid_last_snap);
> -    qemu_uuid_bswap(&header->uuid_link);
> -    qemu_uuid_bswap(&header->uuid_parent);
> +    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
> +    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
> +    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
> +    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
>  }
>  
>  static void vdi_header_to_le(VdiHeader *header)
> @@ -227,10 +227,10 @@ static void vdi_header_to_le(VdiHeader *header)
>      header->block_extra = cpu_to_le32(header->block_extra);
>      header->blocks_in_image = cpu_to_le32(header->blocks_in_image);
>      header->blocks_allocated = cpu_to_le32(header->blocks_allocated);
> -    qemu_uuid_bswap(&header->uuid_image);
> -    qemu_uuid_bswap(&header->uuid_last_snap);
> -    qemu_uuid_bswap(&header->uuid_link);
> -    qemu_uuid_bswap(&header->uuid_parent);
> +    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
> +    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
> +    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
> +    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
>  }
>  
>  static void vdi_header_print(VdiHeader *header)
> diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
> index d78b579a201..02717a8b0dc 100644
> --- a/hw/acpi/vmgenid.c
> +++ b/hw/acpi/vmgenid.c
> @@ -30,8 +30,7 @@ void vmgenid_build_acpi(VmGenIdState *vms, GArray *table_data, GArray *guid,
>       * first, since that's what the guest expects
>       */
>      g_array_set_size(guid, VMGENID_FW_CFG_SIZE - ARRAY_SIZE(guid_le.data));
> -    guid_le = vms->guid;
> -    qemu_uuid_bswap(&guid_le);
> +    guid_le = qemu_uuid_bswap(vms->guid);
>      /* The GUID is written at a fixed offset into the fw_cfg file
>       * in order to implement the "OVMF SDT Header probe suppressor"
>       * see docs/specs/vmgenid.txt for more details
> @@ -149,8 +148,7 @@ static void vmgenid_update_guest(VmGenIdState *vms)
>               * however, will expect the fields to be little-endian.
>               * Perform a byte swap immediately before writing.
>               */
> -            guid_le = vms->guid;
> -            qemu_uuid_bswap(&guid_le);
> +            guid_le = qemu_uuid_bswap(vms->guid);
>              /* The GUID is written at a fixed offset into the fw_cfg file
>               * in order to implement the "OVMF SDT Header probe suppressor"
>               * see docs/specs/vmgenid.txt for more details.
> diff --git a/tests/vmgenid-test.c b/tests/vmgenid-test.c
> index 0a6fb55f2eb..98db43f5a65 100644
> --- a/tests/vmgenid-test.c
> +++ b/tests/vmgenid-test.c
> @@ -110,7 +110,7 @@ static void read_guid_from_memory(QemuUUID *guid)
>      /* The GUID is in little-endian format in the guest, while QEMU
>       * uses big-endian.  Swap after reading.
>       */
> -    qemu_uuid_bswap(guid);
> +    *guid = qemu_uuid_bswap(*guid);
>  }
>  
>  static void read_guid_from_monitor(QemuUUID *guid)
> diff --git a/util/uuid.c b/util/uuid.c
> index ebf06c049ad..5787f0978c1 100644
> --- a/util/uuid.c
> +++ b/util/uuid.c
> @@ -110,10 +110,10 @@ int qemu_uuid_parse(const char *str, QemuUUID *uuid)
>  
>  /* Swap from UUID format endian (BE) to the opposite or vice versa.
>   */
> -void qemu_uuid_bswap(QemuUUID *uuid)
> +QemuUUID qemu_uuid_bswap(QemuUUID uuid)
>  {
> -    assert(QEMU_PTR_IS_ALIGNED(uuid, sizeof(uint32_t)));
> -    bswap32s(&uuid->fields.time_low);
> -    bswap16s(&uuid->fields.time_mid);
> -    bswap16s(&uuid->fields.time_high_and_version);
> +    bswap32s(&uuid.fields.time_low);
> +    bswap16s(&uuid.fields.time_mid);
> +    bswap16s(&uuid.fields.time_high_and_version);
> +    return uuid;
>  }
> -- 
> 2.19.2