Re: [Xen-devel] [PATCH]: PVH: specify xen features strings cleany for PVH

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.01.13 at 00:12, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> wrote:
> On Mon, 21 Jan 2013 12:06:42 +0000
> "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>> >>> On 19.01.13 at 02:35, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
>> >>> wrote:
>> 
>> That's not really better. What I'd like you to do is keep the common
>> part common (i.e. not redundantly defined) and add the PVH-specific
>> bits (with what amounts to an empty string as the non-PVH
>> replacement) on top. Meaning you will likely want a mixture of
>> .ascii and .asciz.
> 
>          ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz 
> "!writable_page_tables|pae_pgdir_above_4gb"PVH_FEATURES_STR);
> 
> Will put NULL char before PVH_FEATURES_STR, so we need:
> 
>          ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .ascii 
> "!writable_page_tables|pae_pgdir_above_4gb"PVH_FEATURES_STR);
> 
> This means PVH_FEATURES_STR has to be defined as:
> 
> #define PVH_FEATURES_STR  
> "|writable_descriptor_tables|auto_translated_physmap|supervisor_mode_kernel|h
> vm_callback_vector\0"
> 
> because 
> #define PVH_FEATURES_STR "|writable_descriptor_tables" \
>                          "|auto_translated_physmap"       
>                          .....
> 
> will put null char after writable_descriptor_tables. Putting .ascii
> above will not work either with concatenation later.
> 
> So, I think what I proposed earlier is the cleanest. Alternately:
> 
> #ifdef CONFIG_XEN_X86_PVH
> 
> #define PVH_FEATURES_STR  
> "|writable_descriptor_tables|auto_translated_physmap|supervisor_mode_kernel|h
> vm_callback_vector\0"
> 
> #else
> #define PVH_FEATURES_STR "\0"
> #endif
> 
> Then:
>         ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .ascii 
> "!writable_page_tables|pae_pgdir_above_4gb"PVH_FEATURES_STR);
> 
> 
> Let me know what you prefer, whats right above, or what I had originally
> last week. I can't figure any other way.

I continue to think that the cleanest is to use something like

ELFNOTE(Xen, XEN_ELFNOTE_FEATURES, .ascii 
"!writable_page_tables|pae_pgdir_above_4gb"; .asciz PVH_FEATURES_STR);

Jan



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