Re: [PATCH] xvmalloc: adjust XVFREE() ordering

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.04.2026 16:32, Jan Beulich wrote:
> What c4f427ec879e ("xen: Swap order of actions in the FREE*() macros") did
> should have been done right away when XVFREE() was introduced.
> 
> Amends: 9102fcd9579f ("mm: introduce xvmalloc() et al and use for grant table 
> allocations")
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

On Arm64, and only for alpine-3.18-gcc-debug-arm64-boot-cpupools, this
reproducibly causes:

diff -u  ./.xen-syms.1.o.sym  ./.xen-syms.2.o.sym
--- ./.xen-syms.1.o.sym
+++ ./.xen-syms.2.o.sym
@@ -7,11 +7,11 @@
 0000000000000000 l    d  .bss  0000000000000000 .bss
 0000000000000000 l    d  .rodata       0000000000000000 .rodata
 0000000000000000 l    d  .note.GNU-stack       0000000000000000 .note.GNU-stack
-0000000000000000 g     O .rodata       0000000000004dd8 .hidden 
symbols_addresses
-0000000000004dd8 g     O .rodata       0000000000000004 .hidden 
symbols_num_addrs
-0000000000004ddc g     O .rodata       0000000000007721 .hidden symbols_names
-000000000000c500 g     O .rodata       0000000000000028 .hidden symbols_markers
-000000000000c528 g     O .rodata       00000000000003b5 .hidden 
symbols_token_table
-000000000000c8de g     O .rodata       0000000000000200 .hidden 
symbols_token_index
+0000000000000000 g     O .rodata       0000000000004de8 .hidden 
symbols_addresses
+0000000000004de8 g     O .rodata       0000000000000004 .hidden 
symbols_num_addrs
+0000000000004dec g     O .rodata       0000000000007749 .hidden symbols_names
+000000000000c538 g     O .rodata       0000000000000028 .hidden symbols_markers
+000000000000c560 g     O .rodata       00000000000003b5 .hidden 
symbols_token_table
+000000000000c916 g     O .rodata       0000000000000200 .hidden 
symbols_token_index

There are only two uses of XVFREE() in code that is built for Arm. I'll
see if I can repro locally with the exact same .config, but I fear my
chances are slim.

It feels wrong to push the patch nevertheless, but it also feels wrong to
have to keep it out.

Jan

> --- a/xen/include/xen/xvmalloc.h
> +++ b/xen/include/xen/xvmalloc.h
> @@ -71,8 +71,9 @@ void *_xvrealloc(void *va, size_t size,
>  
>  /* Free an allocation, and zero the pointer to it. */
>  #define XVFREE(p) do { \
> -    xvfree(p);         \
> +    void *_ptr_ = (p); \
>      (p) = NULL;        \
> +    xvfree(_ptr_);     \
>  } while ( false )
>  
>  static inline void *_xvmalloc_array(