Re: [Xen-devel] [PATCH 1/4] xen/common: Replace incorrect mandatory barriers with SMP barriers

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 5 Dec 2016, Andrew Cooper wrote:
> Mandatory barriers are only for use with reduced-cacheability MMIO mappings.
> 
> All of these uses are just to deal with shared memory between multiple
> processors, so use the smp_*() which are the correct barriers for the purpose.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> 
> Restricting to just the $ARCH maintainers, as this is a project-wide sweep
> ---
>  xen/common/grant_table.c | 2 +-
>  xen/common/time.c        | 4 ++--
>  xen/common/vm_event.c    | 6 +++---
>  3 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
> index e2c4097..a425a9e 100644
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -993,7 +993,7 @@ __gnttab_map_grant_ref(
>      mt = &maptrack_entry(lgt, handle);
>      mt->domid = op->dom;
>      mt->ref   = op->ref;
> -    wmb();
> +    smp_wmb();
>      write_atomic(&mt->flags, op->flags);
>  
>      if ( need_iommu )
> diff --git a/xen/common/time.c b/xen/common/time.c
> index 721ada8..a7caea9 100644
> --- a/xen/common/time.c
> +++ b/xen/common/time.c
> @@ -103,7 +103,7 @@ void update_domain_wallclock_time(struct domain *d)
>  
>      wc_version = &shared_info(d, wc_version);
>      *wc_version = version_update_begin(*wc_version);
> -    wmb();
> +    smp_wmb();
>  
>      sec = wc_sec + d->time_offset_seconds;
>      shared_info(d, wc_sec)    = sec;
> @@ -117,7 +117,7 @@ void update_domain_wallclock_time(struct domain *d)
>      shared_info(d, wc_sec_hi) = sec >> 32;
>  #endif
>  
> -    wmb();
> +    smp_wmb();
>      *wc_version = version_update_end(*wc_version);
>  
>      spin_unlock(&wc_lock);
> diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
> index 907ab40..c6f7d32 100644
> --- a/xen/common/vm_event.c
> +++ b/xen/common/vm_event.c
> @@ -31,9 +31,9 @@
>  #include <xsm/xsm.h>
>  
>  /* for public/io/ring.h macros */
> -#define xen_mb()   mb()
> -#define xen_rmb()  rmb()
> -#define xen_wmb()  wmb()
> +#define xen_mb()   smp_mb()
> +#define xen_rmb()  smp_rmb()
> +#define xen_wmb()  smp_wmb()
>  
>  #define vm_event_ring_lock_init(_ved)  spin_lock_init(&(_ved)->ring_lock)
>  #define vm_event_ring_lock(_ved)       spin_lock(&(_ved)->ring_lock)
> -- 
> 2.1.4
> 

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