All of lore.kernel.org
 help / color / mirror / Atom feed
From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andi Kleen <ak@linux.intel.com>,
	Andrew Lutomirski <luto@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Brian Gerst <brgerst@gmail.com>, Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH v3 8/7] TESTING_ONLY x86/entry: reduce static footprint of idtentry
Date: Tue, 13 Feb 2018 13:41:06 +0100	[thread overview]
Message-ID: <20180213124106.ycilgvmkwv2mrjt6@gmail.com> (raw)
In-Reply-To: <CA+55aFwLTF3EtaQ4OpDv2UM41J=EU7gfemv=eVq+uQi31-usSg@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, Feb 12, 2018 at 1:37 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > Ok, so this does not look _that_ complicated, and the .text savings are
> > significant:
> 
> Honestly, I think we should do it. 3kB of assembly code is noticeable.
> 
> Also, that patch actually allows more cleanups and simplifications.
> Look at the "interrupt" macro, which is used by 'apicinterrupt3', and
> has a number of uses that way.
> 
> That code could be unified a lot, right now it does:
> 
>         testb   $3, CS-ORIG_RAX(%rsp)
>         jz      1f
>         SWAPGS
>         call    switch_to_thread_stack
> 1:
> 
>         ALLOC_PT_GPREGS_ON_STACK
>         SAVE_C_REGS
>         SAVE_EXTRA_REGS
>         ENCODE_FRAME_POINTER
> 
>         testb   $3, CS(%rsp)
>         jz      1f
> 
>         /*
>          * IRQ from user mode.
>          *
>          * We need to tell lockdep that IRQs are off.  We can't do this until
>          * we fix gsbase, and we should do it before enter_from_user_mode
>          * (which can take locks).  Since TRACE_IRQS_OFF idempotent,
>          * the simplest way to handle it is to just call it twice if
>          * we enter from user mode.  There's no reason to optimize this since
>          * TRACE_IRQS_OFF is a no-op if lockdep is off.
>          */
>         TRACE_IRQS_OFF
> 
>         CALL_enter_from_user_mode
> 
> 1:
>         ENTER_IRQ_STACK old_rsp=%rdi
>         /* We entered an interrupt context - irqs are off: */
>         TRACE_IRQS_OFF
> 
> and *all* of that could be in a helper function rather than be
> duplicated. and the apicinterrupt3 macro should end up just expanding
> to
> 
>         callq helper
>         pushq $~(\num)
>         callq \fn
>         jmp ret_from_intr
> 
> instead of expanding to all that code.
> 
> But that would require that same "save_ret" logic.
> 
> So it's not just the idtentry cases that can use this trick.
> 
> I admit that the trick isn't pretty, but it's not *horribly* ugly either.

Ok, agreed!

Dominik, could you please do this on top latest tip:master? I have applied all the 
other patches. Note that patch #8 now conflicts with recent annotation fixes.

Thanks,

	Ingo

      reply	other threads:[~2018-02-13 12:41 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-11 10:49 [PATCH v3 0/7] x86/entry: simplify and unify SAVE/POP_REGS Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 1/7] x86/entry: merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions Dominik Brodowski
2018-02-12 10:15   ` [tip:x86/pti] x86/entry/64: Merge " tip-bot for Dominik Brodowski
2018-02-13  9:00   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 2/7] x86/entry: merge POP_C_REGS and POP_EXTRA_REGS Dominik Brodowski
2018-02-12 10:16   ` [tip:x86/pti] x86/entry/64: Merge the POP_C_REGS and POP_EXTRA_REGS macros into a single POP_REGS macro tip-bot for Dominik Brodowski
2018-02-13  9:01   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 3/7] x86/entry: interleave XOR register clearing with PUSH instructions Dominik Brodowski
2018-02-12 10:16   ` [tip:x86/pti] x86/entry/64: Interleave " tip-bot for Dominik Brodowski
2018-02-13  9:01   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 4/7] x86/entry: introduce PUSH_AND_CLEAN_REGS Dominik Brodowski
2018-02-12 10:17   ` [tip:x86/pti] x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro tip-bot for Dominik Brodowski
2018-02-12 13:29     ` Denys Vlasenko
2018-02-12 13:36       ` David Laight
2018-02-12 13:43         ` Denys Vlasenko
2018-02-12 16:51       ` Linus Torvalds
2018-02-13  9:01   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 5/7] x86/entry: use PUSH_AND_CLEAN_REGS in more cases Dominik Brodowski
2018-02-12 10:17   ` [tip:x86/pti] x86/entry/64: Use " tip-bot for Dominik Brodowski
2018-02-13  9:02   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 6/7] x86/entry: get rid of ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS Dominik Brodowski
2018-02-12 10:18   ` [tip:x86/pti] x86/entry/64: Get rid of the ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS macros tip-bot for Dominik Brodowski
2018-02-13  9:02   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 7/7] x86/entry: indent PUSH_AND_CLEAR_REGS and POP_REGS properly Dominik Brodowski
2018-02-12 10:18   ` [tip:x86/pti] x86/entry/64: Indent " tip-bot for Dominik Brodowski
2018-02-12 20:13     ` [PATCH] x86/entry/64: Remove unused icebp macro Borislav Petkov
2018-02-13  7:36       ` Ingo Molnar
2018-02-13  9:04       ` [tip:x86/pti] x86/entry/64: Remove the unused 'icebp' macro tip-bot for Borislav Petkov
2018-02-13  9:03   ` [tip:x86/pti] x86/entry/64: Indent PUSH_AND_CLEAR_REGS and POP_REGS properly tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 8/7] TESTING_ONLY x86/entry: reduce static footprint of idtentry Dominik Brodowski
2018-02-12  9:37   ` Ingo Molnar
2018-02-12 19:17     ` Linus Torvalds
2018-02-13 12:41       ` Ingo Molnar [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180213124106.ycilgvmkwv2mrjt6@gmail.com \
    --to=mingo@kernel.org \
    --cc=a.p.zijlstra@chello.nl \
    --cc=ak@linux.intel.com \
    --cc=bp@alien8.de \
    --cc=brgerst@gmail.com \
    --cc=dan.j.williams@intel.com \
    --cc=dvlasenk@redhat.com \
    --cc=jpoimboe@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@dominikbrodowski.net \
    --cc=luto@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH v3 8/7] TESTING_ONLY x86/entry: reduce static footprint of idtentry' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.