Re: [PATCH v4 14/17] xen: Add xen_mr_is_memory()

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 30 Apr 2024, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxx>
> 
> Add xen_mr_is_memory() to abstract away tests for the
> xen_memory MR.
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>

There is an important change in this patch below


> ---
>  hw/xen/xen-hvm-common.c | 8 +++++++-
>  include/sysemu/xen.h    | 8 ++++++++
>  system/physmem.c        | 2 +-
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
> index 1627da7398..0267b88d26 100644
> --- a/hw/xen/xen-hvm-common.c
> +++ b/hw/xen/xen-hvm-common.c
> @@ -12,6 +12,12 @@
>  
>  MemoryRegion xen_memory;
>  
> +/* Check for xen memory.  */
> +bool xen_mr_is_memory(MemoryRegion *mr)
> +{
> +    return mr == &xen_memory;
> +}
> +
>  void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr,
>                     Error **errp)
>  {
> @@ -28,7 +34,7 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, 
> MemoryRegion *mr,
>          return;
>      }
>  
> -    if (mr == &xen_memory) {
> +    if (xen_mr_is_memory(mr)) {
>          return;
>      }
>  
> diff --git a/include/sysemu/xen.h b/include/sysemu/xen.h
> index 754ec2e6cb..dc72f83bcb 100644
> --- a/include/sysemu/xen.h
> +++ b/include/sysemu/xen.h
> @@ -34,6 +34,8 @@ void xen_hvm_modified_memory(ram_addr_t start, ram_addr_t 
> length);
>  void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
>                     struct MemoryRegion *mr, Error **errp);
>  
> +bool xen_mr_is_memory(MemoryRegion *mr);
> +
>  #else /* !CONFIG_XEN_IS_POSSIBLE */
>  
>  #define xen_enabled() 0
> @@ -47,6 +49,12 @@ static inline void xen_ram_alloc(ram_addr_t ram_addr, 
> ram_addr_t size,
>      g_assert_not_reached();
>  }
>  
> +static inline bool xen_mr_is_memory(MemoryRegion *mr)
> +{
> +    g_assert_not_reached();
> +    return false;
> +}
> +
>  #endif /* CONFIG_XEN_IS_POSSIBLE */
>  
>  #endif
> diff --git a/system/physmem.c b/system/physmem.c
> index ad7a8c7d95..1a5ffcba2a 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -2227,7 +2227,7 @@ static void *qemu_ram_ptr_length(RAMBlock *block, 
> ram_addr_t addr,
>           * because we don't want to map the entire memory in QEMU.
>           * In that case just map the requested area.
>           */
> -        if (block->offset == 0) {
> +        if (xen_mr_is_memory(block->mr)) {

This changes this check from block->offset == 0 to block->mr ==
&xen_memory. I think that's correct in all cases (x86 machines, ARM
machines) but I wanted to highlight it.

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>





>              return xen_map_cache(block->mr, addr, len, lock, lock,
>                                   is_write);
>          }
> -- 
> 2.40.1
>