From: Borislav Petkov <bp@alien8.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@linux.intel.com>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Mario Gzuk <mariogzuk@technikz.de>
Subject: Re: [PATCH 8/8] x86, cleanups: Simplify sync_core() in the case of no CPUID
Date: Fri, 30 Nov 2012 19:10:37 +0100 [thread overview]
Message-ID: <20121130181037.GE23034@liondog.tnic> (raw)
In-Reply-To: <50B8F4D7.2010204@zytor.com>
On Fri, Nov 30, 2012 at 10:03:03AM -0800, H. Peter Anvin wrote:
> Well, the grand total of serializing instructions are:
>
> INVD, INVEPT, INVLPG, INVVPID, LGDT, LIDT, LLDT, LTR, MOV to CR, MOV
> to DR, WBINVD, WRMSR, CPUID, IRET, RSM.
What about MFENCE with JMP 1f to kill prefetches? Probably too
expensive. Oh and MFENCE is an SSE2 insn so maybe not supported by 486
or something later ...
> >From all of the above, the alternatives case is kinda relevant for virt
> >where we do text_poke_early in a loop for every alternative section
> >so this could pile up to a bunch of vmexits depending on the emulated
> >hardware. Might be worth a replacement if it is noticeable in guests.
>
> This is still boot time, and I really doubt it is measurable in the
> long run. Yes, exists suck, but at least CPUID is generally a quick
> exit, since all the relevant state is in registers.
Agreed.
--
Regards/Gruss,
Boris.
next prev parent reply other threads:[~2012-11-30 18:10 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-28 19:50 [PATCH 0/8] RFC: Remove 386 support H. Peter Anvin
2012-11-28 19:50 ` [PATCH 1/8] x86, 386 removal: Remove CONFIG_M386 from Kconfig H. Peter Anvin
2012-12-01 0:34 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 2/8] x86, 386 removal: Remove CONFIG_CMPXCHG H. Peter Anvin
2012-12-01 0:35 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 3/8] x86, 386 removal: Remove CONFIG_XADD H. Peter Anvin
2012-11-28 20:30 ` Borislav Petkov
2012-12-01 0:36 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 4/8] x86, 386 removal: Remove CONFIG_BSWAP H. Peter Anvin
2012-12-01 0:37 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 5/8] x86, 386 removal: Remove CONFIG_INVLPG H. Peter Anvin
2012-12-01 0:38 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 6/8] x86, 386 removal: Remove CONFIG_X86_WP_WORKS_OK H. Peter Anvin
2012-11-28 20:52 ` Alan Cox
2012-11-28 23:11 ` H. Peter Anvin
2012-12-01 0:42 ` [tip:x86/nuke386] x86, 386 removal: Document Nx586 as a 386 and thus unsupported tip-bot for H. Peter Anvin
2012-12-01 0:39 ` [tip:x86/nuke386] x86, 386 removal: Remove CONFIG_X86_WP_WORKS_OK tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 7/8] x86, 386 removal: Remove CONFIG_X86_POPAD_OK H. Peter Anvin
2012-12-01 0:40 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 8/8] x86, cleanups: Simplify sync_core() in the case of no CPUID H. Peter Anvin
2012-11-28 20:41 ` Borislav Petkov
2012-11-29 0:14 ` H. Peter Anvin
2012-11-29 9:13 ` Borislav Petkov
2012-11-29 21:06 ` H. Peter Anvin
2012-11-29 21:18 ` Borislav Petkov
2012-11-29 21:20 ` H. Peter Anvin
2012-11-29 21:31 ` Borislav Petkov
2012-11-29 21:24 ` H. Peter Anvin
2012-11-29 21:34 ` Borislav Petkov
2012-11-30 17:01 ` Linus Torvalds
2012-11-30 17:28 ` Borislav Petkov
2012-11-30 18:03 ` H. Peter Anvin
2012-11-30 18:10 ` Borislav Petkov [this message]
2012-11-30 18:40 ` H. Peter Anvin
2012-12-01 0:41 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
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