Re: [Qemu-devel] [PATCH 3/9] memory: Add global-locking property to memory regions

[Fam Zheng <famz@redhat.com>]

On Thu, 06/18 18:47, Paolo Bonzini wrote:
> From: Jan Kiszka <jan.kiszka@siemens.com>
> 
> This introduces the memory region property "global_locking". It is true
> by default. By setting it to false, a device model can request BQL-free
> dispatching of region accesses to its r/w handlers. The actual BQL
> break-up will be provided in a separate patch.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  include/exec/memory.h | 26 ++++++++++++++++++++++++++
>  memory.c              | 11 +++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index b61c84f..61791f8 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -180,6 +180,7 @@ struct MemoryRegion {
>      bool rom_device;
>      bool warning_printed; /* For reservations */
>      bool flush_coalesced_mmio;
> +    bool global_locking;
>      MemoryRegion *alias;
>      hwaddr alias_offset;
>      int32_t priority;
> @@ -812,6 +813,31 @@ void memory_region_set_flush_coalesced(MemoryRegion *mr);
>  void memory_region_clear_flush_coalesced(MemoryRegion *mr);
>  
>  /**
> + * memory_region_set_global_locking: Declares the access processing requires
> + *                                   QEMU's global lock.
> + *
> + * When this is invoked, access to this memory regions will be processed while
> + * holding the global lock of QEMU. This is the default behavior of memory
> + * regions.
> + *
> + * @mr: the memory region to be updated.
> + */
> +void memory_region_set_global_locking(MemoryRegion *mr);
> +
> +/**
> + * memory_region_clear_global_locking: Declares that access processing does
> + *                                     not depend on the QEMU global lock.
> + *
> + * By clearing this property, accesses to the memory region will be processed
> + * outside of QEMU's global lock (unless the lock is held on when issuing the
> + * access request). In this case, the device model implementing the access
> + * handlers is responsible for synchronization of concurrency.
> + *
> + * @mr: the memory region to be updated.
> + */
> +void memory_region_clear_global_locking(MemoryRegion *mr);
> +
> +/**
>   * memory_region_add_eventfd: Request an eventfd to be triggered when a word
>   *                            is written to a location.
>   *
> diff --git a/memory.c b/memory.c
> index 03c536b..6b77354 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1004,6 +1004,7 @@ static void memory_region_initfn(Object *obj)
>      mr->ops = &unassigned_mem_ops;
>      mr->enabled = true;
>      mr->romd_mode = true;
> +    mr->global_locking = true;
>      mr->destructor = memory_region_destructor_none;
>      QTAILQ_INIT(&mr->subregions);
>      QTAILQ_INIT(&mr->coalesced);
> @@ -1627,6 +1628,16 @@ void memory_region_clear_flush_coalesced(MemoryRegion *mr)
>      }
>  }
>  
> +void memory_region_set_global_locking(MemoryRegion *mr)
> +{
> +    mr->global_locking = true;
> +}
> +
> +void memory_region_clear_global_locking(MemoryRegion *mr)
> +{
> +    mr->global_locking = false;
> +}
> +
>  void memory_region_add_eventfd(MemoryRegion *mr,
>                                 hwaddr addr,
>                                 unsigned size,
> -- 
> 1.8.3.1
> 
> 
> 

Reviewed-by: Fam Zheng <famz@redhat.com>