Re: [PATCH] xen/grants: fix hypercall continuation for GNTTABOP_cache_flush

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.04.2020 15:07, Juergen Gross wrote:
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -3626,12 +3626,12 @@ do_grant_table_op(
>          if ( unlikely(!guest_handle_okay(cflush, count)) )
>              goto out;
>          rc = gnttab_cache_flush(cflush, &opaque_in, count);
> -        if ( rc > 0 )
> +        if ( rc >= 0 )
>          {
>              guest_handle_add_offset(cflush, rc);
>              uop = guest_handle_cast(cflush, void);
> +            opaque_out = opaque_in;
>          }
> -        opaque_out = opaque_in;
>          break;
>      }
>  
> @@ -3641,7 +3641,7 @@ do_grant_table_op(
>      }
>  
>    out:
> -    if ( rc > 0 || opaque_out != 0 )
> +    if ( rc > 0 || (opaque_out != 0 && rc == 0) )

I disagree with this part - opaque_out shouldn't end up non-zero
when rc < 0, and it won't anymore with the change in the earlier
hunk.

Jan