| Date | Wed, 6 Dec 2017 19:57:58 +0100 | From | Borislav Petkov <> | Subject | Re: [patch 38/60] x86/fixmap: Move cpu entry area into a separate PMD |
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On Mon, Dec 04, 2017 at 03:07:44PM +0100, Thomas Gleixner wrote: > From: Andy Lutomirski <luto@kernel.org> > > This allows the cpu entry area PMDs to be shared between the kernel and > user space page tables. > > [ tglx: Fixed bottom of by one and added guards so other fixmaps can be > added later ] > > Signed-off-by: Andy Lutomirski <luto@kernel.org> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > > --- > arch/x86/include/asm/fixmap.h | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > --- a/arch/x86/include/asm/fixmap.h > +++ b/arch/x86/include/asm/fixmap.h > @@ -134,16 +134,22 @@ enum fixed_addresses { > #ifdef CONFIG_PARAVIRT > FIX_PARAVIRT_BOOTMAP, > #endif > - FIX_TEXT_POKE1, /* reserve 2 pages for text_poke() */ > - FIX_TEXT_POKE0, /* first page is last, because allocation is backward */ > #ifdef CONFIG_X86_INTEL_MID > FIX_LNW_VRTC, > #endif > - /* Fixmap entries to remap the GDTs, one per processor. */ > + FIX_TEXT_POKE1, /* reserve 2 pages for text_poke() */ > + FIX_TEXT_POKE0, /* first page is last, because allocation is backward */ > + > + /* > + * Fixmap entries to remap the IDT, and the per cpu entry areas. > + * Aligend to a PMD boundary.
"Aligned"
> + */ > + FIX_USR_SHARED_TOP = round_up(FIX_TEXT_POKE0 + 1, PTRS_PER_PMD), > FIX_CPU_ENTRY_AREA_TOP, > FIX_CPU_ENTRY_AREA_BOTTOM = FIX_CPU_ENTRY_AREA_TOP + (CPU_ENTRY_AREA_PAGES * NR_CPUS) - 1, > + FIX_USR_SHARED_BOTTOM = round_up(FIX_CPU_ENTRY_AREA_BOTTOM + 2, PTRS_PER_PMD) - 1,
So those look like this here:
FIX_TEXT_POKE0: 0x285, va: 0xffffffffff57a000 FIX_USR_SHARED_TOP: 0x400, va: 0xffffffffff3ff000 FIX_CPU_ENTRY_AREA_TOP: 0x401, va: 0xffffffffff3fe000 FIX_CPU_ENTRY_AREA_BOTTOM: 0x458, va: 0xffffffffff3a7000 FIX_USR_SHARED_BOTTOM: 0x5ff, va: 0xffffffffff200000
and FIX_CPU_ENTRY_AREA_TOP is the one PTE before the last 4K. But we could just as well use the last one too, no? I.e.,
FIX_USR_SHARED_TOP = round_up(FIX_TEXT_POKE0 + 1, PTRS_PER_PMD), FIX_CPU_ENTRY_AREA_TOP = FIX_USR_SHARED_TOP,
?
-- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
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