Re: [PATCH 24/31] hw/ppc/pnv_occ: skip automatic zero-init of large struct

[Harsh Prateek Bora <harshpb@linux.ibm.com>]

On 6/10/25 18:07, Daniel P. Berrangé wrote:
> The 'occ_model_tick' method has a 12k struct used for copying
> data between guest and host. Skip the automatic zero-init of this
> struct to eliminate the performance overhead in the I/O hot path.
> 
> The 'dynamic_data' buffer will be fully initialized when reading
> data from the guest.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   hw/ppc/pnv_occ.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/pnv_occ.c b/hw/ppc/pnv_occ.c
> index fa6f31cb8d..24b789c191 100644
> --- a/hw/ppc/pnv_occ.c
> +++ b/hw/ppc/pnv_occ.c
> @@ -789,7 +789,7 @@ static bool occ_opal_process_command(PnvOCC *occ,
>   
>   static bool occ_model_tick(PnvOCC *occ)
>   {
> -    struct occ_dynamic_data dynamic_data;
> +    QEMU_UNINITIALIZED struct occ_dynamic_data dynamic_data;

Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>

>   
>       if (!occ_read_dynamic_data(occ, &dynamic_data, NULL)) {
>           /* Can't move OCC state field to safe because we can't map it! */