Re: [Xen-devel] [PATCH for-xen-4.5 v4 04/18] x86/boot: use constant in head.S instead of hardcoded value

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.10.14 at 17:52, <daniel.kiper@xxxxxxxxxx> wrote:
> On Fri, Oct 17, 2014 at 04:00:57PM +0100, Andrew Cooper wrote:
>> On 17/10/14 15:11, Daniel Kiper wrote:
>> > ..to access multiboot.mem_lower data.
>> >
>> > Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
>>
>> Fine, but...
>>
>> > ---
>> >  xen/arch/x86/boot/head.S          |    2 +-
>> >  xen/arch/x86/x86_64/asm-offsets.c |    3 +++
>> >  2 files changed, 4 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
>> > index cd43952..0bdbc65 100644
>> > --- a/xen/arch/x86/boot/head.S
>> > +++ b/xen/arch/x86/boot/head.S
>> > @@ -101,7 +101,7 @@ __start:
>> >           */
>> >          testb   $MBI_MEMLIMITS,(%ebx)
>> >          jz      2f                  /* not available? BDA value will be 
> fine */
>> > -        mov     4(%ebx),%edx
>> > +        mov     MBI_mem_lower(%ebx),%edx
>> >          cmp     $0x100,%edx         /* is the multiboot value too small? 
> */
>> >          jb      2f                  /* if so, do not use it */
>> >          shl     $10-4,%edx
>> > diff --git a/xen/arch/x86/x86_64/asm-offsets.c 
> b/xen/arch/x86/x86_64/asm-offsets.c
>> > index 3994f4d..2de9cad 100644
>> > --- a/xen/arch/x86/x86_64/asm-offsets.c
>> > +++ b/xen/arch/x86/x86_64/asm-offsets.c
>> > @@ -163,6 +163,9 @@ void __dummy__(void)
>> >      OFFSET(CPUINFO_features, struct cpuinfo_x86, x86_capability);
>> >      BLANK();
>> >
>> > +    OFFSET(MBI_mem_lower, multiboot_info_t, mem_lower);
>> > +    BLANK();
>> > +
>> >      OFFSET(MB_flags, multiboot_info_t, flags);
>> >      OFFSET(MB_cmdline, multiboot_info_t, cmdline);
>>
>> These are derived from the same struct, so should be declared together,
>> and have consistent naming.
> 
> MB_* stuff is removed by patch #6. Later we have MBD_*, MBI_* and MBI2_* 
> only.

But that's no excuse to make things inconsistent here. Applying
some of these initial trivial patches might still be fine for 4.5.

Jan


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