Messages in this thread Patch in this message | | | Subject | Re: [PATCH] x86: use pgd accessors when cloning a pgd range. | From | Ian Campbell <> | Date | Wed, 27 Oct 2010 18:58:41 +0100 |
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On Wed, 2010-10-27 at 18:44 +0100, Borislav Petkov wrote: > On Wed, Oct 27, 2010 at 10:31:37AM -0700, Jeremy Fitzhardinge wrote: > > > Xen shouldn't have any users of this, since it's used for low-level > > > operations like SMP bootstrap, suspend to RAM, reboot and low-level > > > BIOS functionality. > > > > > Right, but it is being called smack in the middle of setup_arch(). It > > looks like they could be hidden away in > > native_pagetable_setup_start/done though. > > I think I can put the second sync-back clone_pgd_range in > native_pagetable_setup_done but the first one needs to take place right > at the beginning of setup_arch() because a lot of code in-between relies > on swapper_pg_dir containing proper entries. > > Just to make sure I understand you correctly: best it would be for xen > to not have the copy_pgd_range() calls in setup_arch, correct?
Yes, or to ensure that swapper_pg_dir has not yet been marked as a pagetable at this point. Under Xen we are running on swapper_pg_dir when setup_arch is called.
I think we could achieve this within the Xen pvops backend but e.g. the following would likely work also.
(Note, untested. I also omitted the reindent for clarity at this point)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 95a3274..2d89d5a 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -705,12 +705,14 @@ void __init setup_arch(char **cmdline_p) * copy kernel address range established so far and switch * to the proper swapper page table */ + if (read_cr3() != __pa(swapper_pg_dir)) { clone_pgd_range(swapper_pg_dir + KERNEL_PGD_BOUNDARY, initial_page_table + KERNEL_PGD_BOUNDARY, KERNEL_PGD_PTRS); load_cr3(swapper_pg_dir); __flush_tlb_all(); + } #else printk(KERN_INFO "Command line: %s\n", boot_command_line); #endif
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