Re: [Xen-devel] [PATCH] linux-2.6.18/x86_64: remove an inapplicable feature flag

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 03.11.10 at 09:59, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> 
> --- a/arch/x86_64/kernel/head-xen.S
> +++ b/arch/x86_64/kernel/head-xen.S
> @@ -206,6 +206,6 @@
>       ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          .quad,  startup_64)
>       ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, .quad,  hypercall_page)
>       ELFNOTE(Xen, XEN_ELFNOTE_L1_MFN_VALID,   .quad,  
> _PAGE_PRESENT,_PAGE_PRESENT)
> -     ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz, 
> "writable_page_tables|writable_descriptor_tables|auto_translated_physmap|pae_pgdir_above_4gb|supervisor_mode_kernel")
> +     ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz, 
> "writable_page_tables|writable_descriptor_tables|auto_translated_physmap|supervisor_mode_kernel")
>       ELFNOTE(Xen, XEN_ELFNOTE_LOADER,         .asciz, "generic")
>       ELFNOTE(Xen, XEN_ELFNOTE_SUSPEND_CANCEL, .long,  1)

If the flag was removed from the pv-ops 64-bit kernel too, we could
even start warning about inapplicable flags in hypervisor/tools.

What puzzles me more though is that the pv-ops kernel requires
the writable_page_tables feature. Why is that? And assuming it
supports it at all (which seems questionable given that it unlikely
was ever tested), why would it not also indicate support for
writable_descriptor_tables and auto_translated_physmap?

Jan


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