Further use the generic framework from xen/linkage.h. While there drop
excess alignment and move to .bss.

Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
Of course alongside ASM_INT() we could introduce ASM_QUAD() and
ASM_QUAD_LOCAL() (only the latter needed right here) to aid readability.
Thoughts?

--- a/xen/arch/x86/acpi/wakeup_prot.S
+++ b/xen/arch/x86/acpi/wakeup_prot.S
@@ -1,3 +1,5 @@
+#define DATA_FILL 0 /* For the .bss contributions at the bottom. */
+
 #include <asm/asm_defns.h>
 #include <asm/msr-index.h>
 #include <asm/page.h>
@@ -134,13 +136,20 @@ LABEL(s3_resume)
         ret
 END(do_suspend_lowlevel)
 
-.data
-        .align 16
+        .bss
 
-saved_rsp:      .quad   0
-saved_cr0:      .quad   0
+DATA_LOCAL(saved_rsp, 8)
+        .quad   0
+END(saved_rsp)
+DATA_LOCAL(saved_cr0, 8)
+        .quad   0
+END(saved_cr0)
 #ifdef CONFIG_XEN_SHSTK
-saved_ssp:      .quad   0
+DATA_LOCAL(saved_ssp, 8)
+        .quad   0
+END(saved_ssp)
 #endif
 
+        .data
+
 ASM_INT(saved_magic, 0x9abcdef0)

On 02.10.2024 09:41, Jan Beulich wrote:
> Further use the generic framework from xen/linkage.h. While there drop
> excess alignment and move to .bss.
> 
> Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

May I please ask for an ack or otherwise?

Jan

> ---
> Of course alongside ASM_INT() we could introduce ASM_QUAD() and
> ASM_QUAD_LOCAL() (only the latter needed right here) to aid readability.
> Thoughts?
> 
> --- a/xen/arch/x86/acpi/wakeup_prot.S
> +++ b/xen/arch/x86/acpi/wakeup_prot.S
> @@ -1,3 +1,5 @@
> +#define DATA_FILL 0 /* For the .bss contributions at the bottom. */
> +
>  #include <asm/asm_defns.h>
>  #include <asm/msr-index.h>
>  #include <asm/page.h>
> @@ -134,13 +136,20 @@ LABEL(s3_resume)
>          ret
>  END(do_suspend_lowlevel)
>  
> -.data
> -        .align 16
> +        .bss
>  
> -saved_rsp:      .quad   0
> -saved_cr0:      .quad   0
> +DATA_LOCAL(saved_rsp, 8)
> +        .quad   0
> +END(saved_rsp)
> +DATA_LOCAL(saved_cr0, 8)
> +        .quad   0
> +END(saved_cr0)
>  #ifdef CONFIG_XEN_SHSTK
> -saved_ssp:      .quad   0
> +DATA_LOCAL(saved_ssp, 8)
> +        .quad   0
> +END(saved_ssp)
>  #endif
>  
> +        .data
> +
>  ASM_INT(saved_magic, 0x9abcdef0)

On 02/10/2024 8:41 am, Jan Beulich wrote:
> Further use the generic framework from xen/linkage.h. While there drop
> excess alignment and move to .bss.
>
> Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> Of course alongside ASM_INT() we could introduce ASM_QUAD() and
> ASM_QUAD_LOCAL() (only the latter needed right here) to aid readability.
> Thoughts?

Honestly, ASM_INT() hiding a .long is confusing enough already.

ASM_C_{INT,LONG}() wouldn't be as bad.  At least they're clear about
being a particular type in another language.

> --- a/xen/arch/x86/acpi/wakeup_prot.S
> +++ b/xen/arch/x86/acpi/wakeup_prot.S
> @@ -1,3 +1,5 @@
> +#define DATA_FILL 0 /* For the .bss contributions at the bottom. */
> +

I really feel that here is the wrong place for this to live.

Why isn't it in xen/linkage.h?  When is data typically padded with
anything other than 0's?

~Andrew

On 02.10.2024 11:07, Andrew Cooper wrote:
> On 02/10/2024 8:41 am, Jan Beulich wrote:
>> Further use the generic framework from xen/linkage.h. While there drop
>> excess alignment and move to .bss.
>>
>> Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> ---
>> Of course alongside ASM_INT() we could introduce ASM_QUAD() and
>> ASM_QUAD_LOCAL() (only the latter needed right here) to aid readability.
>> Thoughts?
> 
> Honestly, ASM_INT() hiding a .long is confusing enough already.
> 
> ASM_C_{INT,LONG}() wouldn't be as bad.  At least they're clear about
> being a particular type in another language.

I don't think the _C_ would add much; we all know C is the language Xen
is written in. ASM_LONG() / ASM_C_LONG() would not be generalizable, i.e.
couldn't be put in xen/linkage.h without arch customization, as that can
neither expand uniformly to .long nor to .quad. It's all solvable, but
would be getting involved.

>> --- a/xen/arch/x86/acpi/wakeup_prot.S
>> +++ b/xen/arch/x86/acpi/wakeup_prot.S
>> @@ -1,3 +1,5 @@
>> +#define DATA_FILL 0 /* For the .bss contributions at the bottom. */
>> +
> 
> I really feel that here is the wrong place for this to live.
> 
> Why isn't it in xen/linkage.h?  When is data typically padded with
> anything other than 0's?

As per what we currently have, the default data padding is ~0. Personally
I consider this marginally better than 0, but it could of course be
changed.

Jan