Messages in this thread | | | Date | Mon, 7 Jan 2013 16:55:44 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v7u1 08/31] x86, 64bit: early #PF handler set page table |
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On Thu, Jan 03, 2013 at 04:48:28PM -0800, Yinghai Lu wrote: > From: "H. Peter Anvin" <hpa@zytor.com> > > two use cases: > 1. We will support load and run kernel above 4G, and zero_page, ramdisk > will be above 4G, too > 2. need to access ramdisk early to get microcode to update that as > early possible. > > We could use early_iomap to access them, but it will make code to too > messy and hard to unified with 32bit. s/unified/unify/
> > So here comes #PF handler to set page page. > > When #PF happen, handler will use pages in __initdata to set page page
"When a page fault happens, the handler will use pages from __initdata to cover the accessed page."
> to cover accessed page. > > those code and page in __INIT sections, so will not increase ram usages.
Huh, what? Something is in __INIT and will not increase RAM usage?
> The good point is: with help of #PF handler, we can set kernel mapping > from blank, and switch to init_level4_pgt later.
I think you want to say "we can create temporary, ad-hoc kernel mappings and forget them later by switching to init_level4_pgt." ?
> switchover in head_64.S is only using three page to handle kernel > crossing 1G, 512G with shareing page, most insteresting part.
Again, what?
> early_make_pgtable is using kernel high mapping address to access pages > to set page table. > > -v4: Add phys_base offset to make kexec happy, and add > init_mapping_kernel() - Yinghai > -v5: fix compiling with xen, and add back ident level3 and level2 for xen > also move back init_level4_pgt from BSS to DATA again. > because we have to clear it anyway. - Yinghai > -v6: switch to init_level4_pgt in init_mem_mapping. - Yinghai > -v7: remove not needed clear_page for init_level4_page > it is with fill 512,8,0 already in head_64.S - Yinghai > -v8: we need to keep that handler alive until init_mem_mapping and don't > let early_trap_init to trash that early #PF handler. > So split early_trap_pf_init out and move it down. - Yinghai > -v9: switchover only cover kernel space instead of 1G so could avoid > touch possible mem holes. - Yinghai > -v11: change far jmp back to far return to initial_code, that is needed > to fix failure that is reported by Konrad on AMD system. - Yinghai
Those -vXX version lines need to go under the "---" line. Alternatively, you might want to add some of them to the commit message with a proper explanation since they are not that trivial at a first glance, for example the -v5, -v6, -v8, -v9 with a better explanation.
> > Signed-off-by: Yinghai Lu <yinghai@kernel.org>
This needs hpa's S-O-B.
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