Re: [Xen-devel] [PATCH v12 1/3] xen/mem_sharing: VM forking

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.03.2020 18:04, Tamas K Lengyel wrote:
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -2202,6 +2202,17 @@ int domain_relinquish_resources(struct domain *d)
>              ret = relinquish_shared_pages(d);
>              if ( ret )
>                  return ret;
> +
> +            /*
> +             * If the domain is forked, decrement the parent's pause count
> +             * and release the domain.
> +             */
> +            if ( mem_sharing_is_fork(d) )
> +            {
> +                domain_unpause(d->parent);
> +                put_domain(d->parent);
> +                d->parent = NULL;

I think you want to clear the field before putting the reference,
to make sure possible readers of it won't see it non-NULL when
the domain is already being cleaned up, or even gone.

With this, applicable parts of the change
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

I'll try to keep an eye on when you and Roger have settled on the
remaining aspects, to determine when this (probably v13) can be
committed.

> --- a/xen/include/asm-x86/mem_sharing.h
> +++ b/xen/include/asm-x86/mem_sharing.h
> @@ -77,6 +77,14 @@ static inline int mem_sharing_unshare_page(struct domain 
> *d,
>      return rc;
>  }
>  
> +static inline bool mem_sharing_is_fork(struct domain *d)

const? (then also in the stub further down)

Jan