Re: [PATCH v2 1/2] exec: Check Xen is enabled before calling the Xen API

[Juan Quintela <quintela@redhat.com>]

Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/exec/ram_addr.h | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 5e59a3d8d7..dd8713179e 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -330,7 +330,9 @@ static inline void cpu_physical_memory_set_dirty_range(ram_addr_t start,
>          }
>      }
>  
> -    xen_hvm_modified_memory(start, length);
> +    if (xen_enabled()) {
> +        xen_hvm_modified_memory(start, length);
> +    }
>  }
>  
>  #if !defined(_WIN32)
> @@ -388,7 +390,9 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
>              }
>          }
>  
> -        xen_hvm_modified_memory(start, pages << TARGET_PAGE_BITS);
> +        if (xen_enabled()) {
> +            xen_hvm_modified_memory(start, pages << TARGET_PAGE_BITS);
> +        }
>      } else {
>          uint8_t clients = tcg_enabled() ? DIRTY_CLIENTS_ALL : DIRTY_CLIENTS_NOCODE;

I don't object moving the xen code to accell.  But I think that this
change is bad.

On the following patch:
- You export xen_allowed
  (ok, it was already exported, but I think it shouldn't)

(master)$ find . -type f | xargs grep xen_allowed
./hw/xen/xen-common.c:    ac->allowed = &xen_allowed;
./include/hw/xen/xen.h:extern bool xen_allowed;
./include/hw/xen/xen.h:    return xen_allowed;
./softmmu/vl.c:bool xen_allowed;

This are all the users that I can find.

And xen_havm_modified_memory() is an empty function if xen is not
compiled in.  And in the case that xen is compiled in, the 1st thing
that it checks is:

   if (unlikely(xen_in_migration)) {

That is way more restrictive that xen_enabled().

So, I think that it is better to drop this patch, maintain next one, but
just un-exporting xen_allowed.

What do you think?

Later, Juan.