Re: [Qemu-devel] [PATCH] nbd: Don't use *_to_cpup() functions

[Paolo Bonzini]

On 10/06/2016 17:00, Peter Maydell wrote:
> The *_to_cpup() functions are not very useful, as they simply do
> a pointer dereference and then a *_to_cpu(). Instead use either:
>  * ld*_*_p(), if the data is at an address that might not be
>    correctly aligned for the load
>  * a local dereference and *_to_cpu(), if the pointer is
>    the correct type and known to be correctly aligned
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> The motivation is to be able to drop *_to_cpup() entirely;
> we don't have many places that use it.

Good idea indeed.  Queued both patches.

Paolo

> ---
>  nbd/client.c |  8 ++++----
>  nbd/server.c | 10 +++++-----
>  qemu-nbd.c   |  4 ++--
>  3 files changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/nbd/client.c b/nbd/client.c
> index 31b88f3..bb8981f 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -572,7 +572,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name, uint32_t *flags,
>              error_setg(errp, "Failed to read export flags");
>              goto fail;
>          }
> -        *flags = be32_to_cpup(flags);
> +        *flags = be32_to_cpu(*flags);
>      } else {
>          error_setg(errp, "Bad magic received");
>          goto fail;
> @@ -726,9 +726,9 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, struct 
> nbd_reply *reply)
>         [ 7 .. 15]    handle
>       */
>  
> -    magic = be32_to_cpup((uint32_t*)buf);
> -    reply->error  = be32_to_cpup((uint32_t*)(buf + 4));
> -    reply->handle = be64_to_cpup((uint64_t*)(buf + 8));
> +    magic = ldl_be_p(buf);
> +    reply->error  = ldl_be_p(buf + 4);
> +    reply->handle = ldq_be_p(buf + 8);
>  
>      reply->error = nbd_errno_to_system_errno(reply->error);
>  
> diff --git a/nbd/server.c b/nbd/server.c
> index b2cfeb9..91471f1 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -646,11 +646,11 @@ static ssize_t nbd_receive_request(QIOChannel *ioc, 
> struct nbd_request *request)
>         [24 .. 27]   len
>       */
>  
> -    magic = be32_to_cpup((uint32_t*)buf);
> -    request->type  = be32_to_cpup((uint32_t*)(buf + 4));
> -    request->handle = be64_to_cpup((uint64_t*)(buf + 8));
> -    request->from  = be64_to_cpup((uint64_t*)(buf + 16));
> -    request->len   = be32_to_cpup((uint32_t*)(buf + 24));
> +    magic = ldl_be_p(buf);
> +    request->type   = ldl_be_p(buf + 4);
> +    request->handle = ldq_be_p(buf + 8);
> +    request->from   = ldq_be_p(buf + 16);
> +    request->len    = ldl_be_p(buf + 24);
>  
>      TRACE("Got request: "
>            "{ magic = 0x%x, .type = %d, from = %" PRIu64" , len = %u }",
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 6554f0a..9519db3 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -154,8 +154,8 @@ static void read_partition(uint8_t *p, struct 
> partition_record *r)
>      r->end_cylinder = p[7] | ((p[6] << 2) & 0x300);
>      r->end_sector = p[6] & 0x3f;
>  
> -    r->start_sector_abs = le32_to_cpup((uint32_t *)(p +  8));
> -    r->nb_sectors_abs   = le32_to_cpup((uint32_t *)(p + 12));
> +    r->start_sector_abs = ldl_le_p(p + 8);
> +    r->nb_sectors_abs   = ldl_le_p(p + 12);
>  }
>  
>  static int find_partition(BlockBackend *blk, int partition,
>