Hi Michal, Julien,
> On 28 Jan 2025, at 09:40, Michal Orzel <michal.or...@amd.com> wrote:
>
> On Arm32, when CONFIG_PHYS_ADDR_T_32 is set, a build failure is observed:
> common/device-tree/bootfdt.c: In function 'build_assertions':
> ./include/xen/macros.h:47:31: error: static assertion failed:
> "!(alignof(struct membanks) != 8)"
> 47 | #define BUILD_BUG_ON(cond) ({ _Static_assert(!(cond), "!(" #cond ")");
> })
> | ^~~~~~~~~~~~~~
> common/device-tree/bootfdt.c:31:5: note: in expansion of macro 'BUILD_BUG_ON'
> 31 | BUILD_BUG_ON(alignof(struct membanks) != 8);
>
> When CONFIG_PHYS_ADDR_T_32 is set, paddr_t is defined as unsigned long,
> therefore the struct membanks alignment is 4B and not 8B. The check is
> there to ensure the struct membanks and struct membank, which is a
> member of the former, are equally aligned. Therefore modify the check to
> compare alignments obtained via alignof not to rely on hardcoded
> values.
>
> Fixes: 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory bank
> structures")
> Signed-off-by: Michal Orzel <michal.or...@amd.com>
> Release-Acked-by: Oleksii Kurochko <oleksii.kuroc...@gmail.com>
> ---
> Changes in v2:
> - modify the check to test against alignment of struct membank
> ---
> xen/common/device-tree/bootfdt.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/xen/common/device-tree/bootfdt.c
> b/xen/common/device-tree/bootfdt.c
> index 47386d4fffea..529c91e603ab 100644
> --- a/xen/common/device-tree/bootfdt.c
> +++ b/xen/common/device-tree/bootfdt.c
> @@ -27,8 +27,8 @@ static void __init __maybe_unused build_assertions(void)
> */
> BUILD_BUG_ON((offsetof(struct membanks, bank) !=
> offsetof(struct meminfo, bank)));
> - /* Ensure "struct membanks" is 8-byte aligned */
> - BUILD_BUG_ON(alignof(struct membanks) != 8);
> + /* Ensure "struct membanks" and "struct membank" are equally aligned */
> + BUILD_BUG_ON(alignof(struct membanks) != alignof(struct membank));
Apologies for not catching the issue for your v1, probably I didn't understand
very well the test itself,
why are we checking that the structure have the same alignment?
I see we check the offset of `(struct membanks).bank` against `(struct
meminfo|struct shared_meminfo).bank`,
isn't that enough?
For sure I’m missing something...
Anyway I tested this:
Tested-by: Luca Fancellu <luca.fance...@arm.com>
> }
>
> static bool __init device_tree_node_is_available(const void *fdt, int node)
> --
> 2.25.1
>
>
