From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Borislav Petkov <bp@suse.de>, Andi Kleen <ak@linux.intel.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 8/9] x86/mm: Make __VIRTUAL_MASK_SHIFT dynamic
Date: Wed, 14 Feb 2018 20:55:48 +0300 [thread overview]
Message-ID: <20180214175548.6uxpm3bspmgqi7hs@node.shutemov.name> (raw)
In-Reply-To: <CALCETrVafx9kZwsJrihUxKszio9rJCPZJHnWSh3QC992o=zxnA@mail.gmail.com>
On Wed, Feb 14, 2018 at 05:22:58PM +0000, Andy Lutomirski wrote:
> On Wed, Feb 14, 2018 at 11:16 AM, Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> > For boot-time switching between paging modes, we need to be able to
> > adjust virtual mask shifts.
> >
> > The change doesn't affect the kernel image size much:
> >
> > text data bss dec hex filename
> > 8628892 4734340 1368064 14731296 e0c820 vmlinux.before
> > 8628966 4734340 1368064 14731370 e0c86a vmlinux.after
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> > arch/x86/entry/entry_64.S | 12 ++++++++++++
> > arch/x86/include/asm/page_64_types.h | 2 +-
> > arch/x86/mm/dump_pagetables.c | 12 ++++++++++--
> > arch/x86/mm/kaslr.c | 4 +++-
> > 4 files changed, 26 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> > index cd216c9431e1..1608b13a0b36 100644
> > --- a/arch/x86/entry/entry_64.S
> > +++ b/arch/x86/entry/entry_64.S
> > @@ -260,8 +260,20 @@ GLOBAL(entry_SYSCALL_64_after_hwframe)
> > * Change top bits to match most significant bit (47th or 56th bit
> > * depending on paging mode) in the address.
> > */
> > +#ifdef CONFIG_X86_5LEVEL
> > + testl $1, pgtable_l5_enabled(%rip)
> > + jz 1f
> > + shl $(64 - 57), %rcx
> > + sar $(64 - 57), %rcx
> > + jmp 2f
> > +1:
> > + shl $(64 - 48), %rcx
> > + sar $(64 - 48), %rcx
> > +2:
> > +#else
> > shl $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
> > sar $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
> > +#endif
>
> Eww.
>
> Can't this be ALTERNATIVE "shl ... sar ...", "shl ... sar ...",
> X86_FEATURE_5LEVEL or similar?
Optimization comes in a separate patch:
https://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git/commit/?h=la57/boot-switching/wip&id=015fa3576a7f2b8bd271096bb3a12b06cdc845af
--
Kirill A. Shutemov
--
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next prev parent reply other threads:[~2018-02-14 17:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-14 11:16 [PATCH 0/9] x86/mm: Dynamic memory layout Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 1/9] x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52 Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 2/9] mm/zsmalloc: Prepare to variable MAX_PHYSMEM_BITS Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 3/9] x86/mm: Make virtual memory layout movable for CONFIG_X86_5LEVEL Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 4/9] x86: Introduce pgtable_l5_enabled Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 5/9] x86/mm: Make LDT_BASE_ADDR dynamic Kirill A. Shutemov
2018-02-14 13:32 ` Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 6/9] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 7/9] x86/mm: Make MAX_PHYSADDR_BITS and MAX_PHYSMEM_BITS dynamic Kirill A. Shutemov
2018-02-14 11:16 ` [PATCH 8/9] x86/mm: Make __VIRTUAL_MASK_SHIFT dynamic Kirill A. Shutemov
2018-02-14 17:22 ` Andy Lutomirski
2018-02-14 17:55 ` Kirill A. Shutemov [this message]
2018-02-14 18:02 ` Andy Lutomirski
2018-02-14 11:16 ` [PATCH 9/9] x86/mm: Adjust virtual address space layout in early boot Kirill A. Shutemov
2018-02-14 12:10 ` Ingo Molnar
2018-02-14 12:19 ` Kirill A. Shutemov
2018-02-14 12:26 ` Ingo Molnar
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