* Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote: > On Thu, Sep 28, 2017 at 10:25:14AM +0200, Ingo Molnar wrote: > > > > * Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > > > > > For boot-time switching between paging modes, we need to be able to > > > adjust size of physical address space at runtime. > > > > > > As part of making physical address space size variable, we have to make > > > X86_5LEVEL dependent on SPARSEMEM_VMEMMAP. !SPARSEMEM_VMEMMAP > > > configuration doesn't work well with variable MAX_PHYSMEM_BITS. > > > > > > Affect on kernel image size: > > > > > > text data bss dec hex filename > > > 10710340 4880000 860160 16450500 fb03c4 vmlinux.before > > > 10710666 4880000 860160 16450826 fb050a vmlinux.after > > > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > > --- > > > arch/x86/Kconfig | 1 + > > > arch/x86/include/asm/pgtable_64_types.h | 2 +- > > > arch/x86/include/asm/sparsemem.h | 9 ++------- > > > arch/x86/kernel/setup.c | 5 ++--- > > > 4 files changed, 6 insertions(+), 11 deletions(-) > > > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > > index 6a15297140ff..f75723d62c25 100644 > > > --- a/arch/x86/Kconfig > > > +++ b/arch/x86/Kconfig > > > @@ -1403,6 +1403,7 @@ config X86_PAE > > > config X86_5LEVEL > > > bool "Enable 5-level page tables support" > > > depends on X86_64 > > > + depends on SPARSEMEM_VMEMMAP > > > > Adding a 'depends on' to random kernel internal implementational details, to > > support new hardware, sucks as an UI, as it will just randomly hide/show the new > > hardware option if certain magic Kconfig combinations are set. > > > > Please check how other architectures are doing it. (Hint: they are using select.) > > > > Also, what is the real dependency here? Why don't the other memory models work, > > what's the failure mode - won't build, won't boot, or misbehaves in some other > > way? > > I won't build. > > For !SPARSEMEM_VMEMMAP SECTIONS_WIDTH depends on MAX_PHYSMEM_BITS: > > SECTIONS_WIDTH > SECTIONS_SHIFT > MAX_PHYSMEM_BITS > > And SECTIONS_WIDTH is used on per-processor stage, it doesn't work if it's > dyncamic. See include/linux/page-flags-layout.h. Ok, this would be a good addition to the changelog. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
