Messages in this thread | | | Date | Mon, 18 Apr 2011 18:21:05 +0100 | From | Stefano Stabellini <> | Subject | Re: [PATCH 2/4] x86,xen: introduce x86_init.mapping.pagetable_reserve |
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On Mon, 18 Apr 2011, H. Peter Anvin wrote: > On 04/18/2011 07:09 AM, Stefano Stabellini wrote: > > > > Sorry, I don't mean to be pushy, it is just that I'll be AFK for 12 days > > starting from next Friday and I think that this issue should really be > > fixed in time for the 2.6.39 release, otherwise no 2.6.39 kernels will > > be able to boot on any xen system. > > YOU STILL HAVEN'T PROPOSED ANY SEMANTICS. > > The semantics of a hook is a description of what the preconditions are, > what the postconditions are, and what exactly they are allowed or not > allowed to do. > > This is a real pain to do, *exactly because hooks are a real pain*. > Most hooks that have been put in has been "oh, just do something at > point X in the code", which is a case of definition by implementation, > which is exactly how we ended up with the current mess. >
x86_init.mapping.pagetable_setup_start(start, max_end)
Notifies the subarch that the kernel early startup intends to use pages as page table pages. These pages will have physical addresses in the range start..max_end.
Can be called multiple times to setup kernel page table pages, always in a pair with x86_init.mapping.pagetable_setup_done. It must be called before x86_init.paging.pagetable_setup_start().
Preconditions: no kernel code after the 32-bit kernel entry point has hooked any new page table pages into the active page table except between a pair of x86_init.mapping.pagetable_setup_start and x86_init.mapping.pagetable_setup_done.
Postcondition: pages in the range start..max_end may be used as page table pages and hooked into active page tables. Pages in this range may NOT be used for any other purpose.
x86_init.mapping.pagetable_setup_done(real_end)
Notifies the subarch that the initial memory mapping is complete, and of the actual range of pages used.
Preconditions:
x86_init.mapping.pagetable_setup_start was previously called; the arguments to the calls must satisfy start <= real_end <= max_end
The pages in the range start..real_end have been hooked into the active page table. The pages in the range real_end..max_end are not currently in use.
Postconditions:
Pages in the range real_end..max_end may be used as normal memory.
Pages in the range start..real_end might be hooked into the active page table and cannot be used for other purposes.
New page table pages must be allocated using pv_mmu_ops.alloc_pte/pmd/pud.
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