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From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Willy Tarreau <w@1wt.eu>, Juergen Gross <jgross@suse.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()
Date: Wed, 13 Nov 2019 22:41:38 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.21.1911132237410.2507@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CAHk-=whNAEuNPU3Oy_-EpjOojpysWcCh4uqDgOt2RjBNx2xBSg@mail.gmail.com>

On Wed, 13 Nov 2019, Linus Torvalds wrote:
> On Wed, Nov 13, 2019 at 1:02 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > +int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> > +                   unsigned long arg, struct task_struct *p, unsigned long tls)
> ...
> > +#ifdef CONFIG_X86_64
> ..
> > +#else
> > +       /* Clear all status flags including IF and set fixed bit. */
> > +       frame->flags = X86_EFLAGS_FIXED;
> > +#endif
> 
> Hmm. The unification I like, but it also shows these differences that
> I don't remember the reason for.
> 
> Remind me why __switch_to_asm() on 32-bit safes eflags, but we don't
> do it on x86-64?
> 
> The comment just talks about callee-saved registers, but flags isn't
> callee-saved, so there's something else going on.
> 
> This patch clearly doesn't change anything, I'm not complaining about
> the patch at all. I'm just wondering about the odd difference that the
> patch exposes.

See commit: 64604d54d311 ("sched/x86_64: Don't save flags on context switch")

We need "only" make objtool support 32bit :)

Thanks,

	tglx

  reply	other threads:[~2019-11-13 21:41 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-13 20:42 [patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Thomas Gleixner
2019-11-13 20:42 ` [patch V3 01/20] x86/ptrace: Prevent truncation of bitmap size Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 02/20] x86/process: Unify copy_thread_tls() Thomas Gleixner
2019-11-13 21:10   ` Linus Torvalds
2019-11-13 21:41     ` Thomas Gleixner [this message]
2019-11-13 22:10       ` Linus Torvalds
2019-11-13 22:33         ` Thomas Gleixner
2019-11-13 21:44     ` Brian Gerst
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 03/20] x86/cpu: Unify cpu_init() Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 04/20] x86/tss: Fix and move VMX BUILD_BUG_ON() Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 05/20] x86/iopl: Cleanup include maze Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 06/20] x86/ioperm: Simplify first ioperm() invocation logic Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 07/20] x86/ioperm: Avoid bitmap allocation if no permissions are set Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 08/20] x86/io: Speedup schedule out of I/O bitmap user Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 09/20] x86/tss: Move I/O bitmap data into a seperate struct Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 10/20] x86/ioperm: Move iobitmap data into a struct Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 11/20] x86/ioperm: Add bitmap sequence number Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 12/20] x86/ioperm: Move TSS bitmap update to exit to user work Thomas Gleixner
2019-11-13 21:19   ` Linus Torvalds
2019-11-13 21:21     ` Linus Torvalds
2019-11-13 21:44       ` Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 13/20] x86/ioperm: Remove bitmap if all permissions dropped Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 14/20] x86/ioperm: Share I/O bitmap if identical Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 15/20] selftests/x86/ioperm: Extend testing so the shared bitmap is exercised Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 16/20] x86/iopl: Fixup misleading comment Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 17/20] x86/iopl: Restrict iopl() permission scope Thomas Gleixner
2019-11-14 18:13   ` Borislav Petkov
2019-11-14 18:39     ` Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 18/20] x86/iopl: Remove legacy IOPL option Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 19/20] x86/ioperm: Extend IOPL config to control ioperm() as well Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:43 ` [patch V3 20/20] selftests/x86/iopl: Extend test to cover IOPL emulation Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-14  8:43 ` [patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Peter Zijlstra

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