Re: [PATCHv2 3/3] x86/64/mm: Make 5-level paging support unconditional

[Kirill A. Shutemov]

On Fri, May 16, 2025 at 02:47:46PM +0300, Kirill A. Shutemov wrote:
> On Fri, May 16, 2025 at 01:29:27PM +0200, Jürgen Groß wrote:
> > On 16.05.25 13:09, Kirill A. Shutemov wrote:
> > > On Fri, May 16, 2025 at 12:42:21PM +0200, Jürgen Groß wrote:
> > > > On 16.05.25 11:15, Kirill A. Shutemov wrote:
> > > > > Both Intel and AMD CPUs support 5-level paging, which is expected to
> > > > > become more widely adopted in the future.
> > > > > 
> > > > > Remove CONFIG_X86_5LEVEL and ifdeffery for it to make it more readable.
> > > > > 
> > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > > > > Suggested-by: Borislav Petkov <bp@xxxxxxxxx>
> > > > > ---
> > > > >    Documentation/arch/x86/cpuinfo.rst            |  8 +++----
> > > > >    .../arch/x86/x86_64/5level-paging.rst         |  9 --------
> > > > >    arch/x86/Kconfig                              | 22 +------------------
> > > > >    arch/x86/Kconfig.cpufeatures                  |  4 ----
> > > > >    arch/x86/boot/compressed/pgtable_64.c         | 11 ++--------
> > > > >    arch/x86/boot/header.S                        |  4 ----
> > > > >    arch/x86/boot/startup/map_kernel.c            |  5 +----
> > > > >    arch/x86/include/asm/page_64.h                |  2 --
> > > > >    arch/x86/include/asm/page_64_types.h          |  7 ------
> > > > >    arch/x86/include/asm/pgtable_64_types.h       | 18 ---------------
> > > > >    arch/x86/kernel/alternative.c                 |  2 +-
> > > > >    arch/x86/kernel/head64.c                      |  2 --
> > > > >    arch/x86/kernel/head_64.S                     |  2 --
> > > > >    arch/x86/mm/init.c                            |  4 ----
> > > > >    arch/x86/mm/pgtable.c                         |  2 +-
> > > > >    drivers/firmware/efi/libstub/x86-5lvl.c       |  2 +-
> > > > >    16 files changed, 10 insertions(+), 94 deletions(-)
> > > > 
> > > > There are some instances of:
> > > > 
> > > > #if CONFIG_PGTABLE_LEVELS >= 5
> > > > 
> > > > in 64-bit-only code under arch/x86, which could be simplified, too.
> > > > 
> > > > They are still correct, but I wanted to hint at further code removals
> > > > being possible.
> > > 
> > > Okay, fair enough. Fixup is below.
> > > 
> > > Did I miss anything else?
> > 
> > Yes.
> > 
> > One more instance in arch/x86/xen/mmu_pv.c,
> 
> Ah. Right.
> 
> > one in arch/x86/include/asm/paravirt.h,
> > one in arch/x86/include/asm/paravirt_types.h,
> > one in arch/x86/kernel/paravirt.c
> 
> Hm. Is paravirt 64-bit only?

Oh. It is PARAVIRT_XXL thingy which is only used by XEN_PV which is 64-bit
only, right?

Do we want to make PARAVIRT_XXL explicitly 64-bit only?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov