Re: [Qemu-trivial] [PATCH] block/nvme: Remove QEMU_PACKED from naturally aligned NVMeRegs struct

[Peter Maydell]

On Mon, 25 Feb 2019 at 11:59, Thomas Huth <address@hidden> wrote:
>
> The QEMU_PACKED is causing a compiler warning/error with GCC 9:
>
>   CC      block/nvme.o
> block/nvme.c: In function ‘nvme_create_queue_pair’:
> block/nvme.c:209:22: error: taking address of packed member of
>  ‘struct <anonymous>’ may result in an unaligned pointer value
>  [-Werror=address-of-packed-member]
>   209 |     q->sq.doorbell = &s->regs->doorbells[idx * 2 * s->doorbell_scale];
>
> All members of the struct are naturally aligned, so there should
> not be the need for QEMU_PACKED here, and the following QEMU_BUILD_BUG_ON
> also ensures that there is no padding. Thus simply remove the QEMU_PACKED
> here.
>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1817525
> Reported-by: Satheesh Rajendran <address@hidden>
> Signed-off-by: Thomas Huth <address@hidden>
> ---
>  block/nvme.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/nvme.c b/block/nvme.c
> index b5952c9..6c2ce7d 100644
> --- a/block/nvme.c
> +++ b/block/nvme.c
> @@ -82,7 +82,7 @@ typedef volatile struct {
>      uint8_t  reserved1[0xec0];
>      uint8_t  cmd_set_specfic[0x100];
>      uint32_t doorbells[];
> -} QEMU_PACKED NVMeRegs;
> +} NVMeRegs;
>
>  QEMU_BUILD_BUG_ON(offsetof(NVMeRegs, doorbells) != 0x1000);
>
Reviewed-by: Peter Maydell <address@hidden>

thanks
-- PMM