> On 3 Dec 2021, at 10:58, Jan Beulich <jbeul...@suse.com> wrote:
>
> While be12fcca8b78 ("efi: fix alignment of function parameters in compat
> mode") intentionally bounced them both ways to avoid any functional
> change so close to the release of 4.16, the bouncing-in shouldn't really
> be needed. In exchange the local variables need to gain initializers to
> avoid copying back prior stack contents.
>
Reviewed-by: Luca Fancellu <luca.fance...@arm.com>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> --- a/xen/common/efi/runtime.c
> +++ b/xen/common/efi/runtime.c
> @@ -608,7 +608,15 @@ int efi_runtime_call(struct xenpf_efi_ru
>
> case XEN_EFI_query_variable_info:
> {
> - uint64_t max_store_size, remain_store_size, max_size;
> + /*
> + * Put OUT variables on the stack to make them 8 byte aligned when
> + * called from the compat handler, as their placement in
> + * compat_pf_efi_runtime_call will make them 4 byte aligned instead
> + * and compilers may validly complain. This is done regardless of
> + * whether called from the compat handler or not, as it's not worth
> + * the extra logic to differentiate.
> + */
> + uint64_t max_store_size = 0, remain_store_size = 0, max_size = 0;
>
> if ( op->misc & ~XEN_EFI_VARINFO_BOOT_SNAPSHOT )
> return -EINVAL;
> @@ -642,21 +650,6 @@ int efi_runtime_call(struct xenpf_efi_ru
> if ( !efi_enabled(EFI_RS) || (efi_rs->Hdr.Revision >> 16) < 2 )
> return -EOPNOTSUPP;
>
> - /*
> - * Bounce the variables onto the stack to make them 8 byte aligned
> when
> - * called from the compat handler, as their placement in
> - * compat_pf_efi_runtime_call will make them 4 byte aligned instead
> and
> - * and compilers may validly complain.
> - *
> - * Note that while the function parameters are OUT only, copy the
> - * values here anyway just in case. This is done regardless of
> whether
> - * called from the compat handler or not, as it's not worth the extra
> - * logic to differentiate.
> - */
> - max_store_size = op->u.query_variable_info.max_store_size;
> - remain_store_size = op->u.query_variable_info.remain_store_size;
> - max_size = op->u.query_variable_info.max_size;
> -
> state = efi_rs_enter();
> if ( !state.cr3 )
> return -EOPNOTSUPP;
>
>
