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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>,
	Andi Kleen <ak@linux.intel.com>, Paul Turner <pjt@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linux-foundation.org>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Kees Cook <keescook@google.com>, Rik van Riel <riel@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Jiri Kosina <jikos@kernel.org>, <gnomes@lxorguk.ukuu.org.uk>,
	Thomas Lendacky <Thomas.Lendacky@amd.com>
Subject: Re: [PATCH v5 02/12] x86/retpoline: Add initial retpoline support
Date: Sat, 6 Jan 2018 21:34:25 +0000	[thread overview]
Message-ID: <420b6855-714a-1eaf-0a37-5c73a661cfd5@citrix.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1801062222430.2376@nanos>

On 06/01/18 21:23, Thomas Gleixner wrote:
> On Sat, 6 Jan 2018, Andrew Cooper wrote:
>> On 06/01/18 11:49, David Woodhouse wrote:
>>> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
>>> index 372ba3f..40e6e54 100644
>>> --- a/arch/x86/kernel/cpu/common.c
>>> +++ b/arch/x86/kernel/cpu/common.c
>>> @@ -904,6 +904,11 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
>>>  
>>>  	setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
>>>  	setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
>>> +#ifdef CONFIG_RETPOLINE
>>> +	setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
>>> +	if (c->x86_vendor == X86_VENDOR_AMD)
>>> +		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
>> This isn't safe.  It needs to be dependant on finding that LFENCEs are
>> actually dispatch serialising.
>>
>> In particular, when virtualised, you'll most likely be saddled with the
>> hypervisors choice of setting, in which case you need to use retpoline
>> as a fallback.
> On bare metal we are sure, the virtualization part is a different question.

Leaving virtualisation to one side, how does this cope with pre-SSE2
hardware?

~Andrew

  reply	other threads:[~2018-01-06 21:34 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-06 11:49 [PATCH v5 00/12] Retpoline: Avoid speculative indirect calls in kernel David Woodhouse
2018-01-06 11:49 ` [PATCH v5 01/12] x86/spectre: Add X86_BUG_SPECTRE_V[12] David Woodhouse
2018-01-06 21:05   ` [tip:x86/pti] x86/cpufeatures: " tip-bot for David Woodhouse
2018-01-06 11:49 ` [PATCH v5 02/12] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-06 17:32   ` David Woodhouse
2018-01-06 18:05   ` [PATCH v5.1 " David Woodhouse
2018-01-06 18:35   ` [PATCH v5 " Eric Biggers
2018-01-06 19:17     ` David Woodhouse
2018-01-06 21:16   ` Andrew Cooper
2018-01-06 21:21     ` Woodhouse, David
2018-01-07  1:44       ` Tom Lendacky
2018-01-06 21:23     ` Thomas Gleixner
2018-01-06 21:34       ` Andrew Cooper [this message]
2018-01-06 21:49         ` Woodhouse, David
2018-01-06 11:49 ` [PATCH v5 03/12] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-06 11:49 ` [PATCH v5 04/12] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 05/12] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
2018-01-06 18:13   ` Linus Torvalds
2018-01-06 19:53     ` Thomas Gleixner
2018-01-07  1:27       ` Linus Torvalds
2018-01-06 11:49 ` [PATCH v5 06/12] x86/retpoline/hyperv: Convert " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 07/12] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 08/12] x86/retpoline/checksum32: Convert assembler " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 09/12] x86/retpoline/irq32: " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 10/12] x86/retpoline: Add boot time option to disable retpoline David Woodhouse
2018-01-06 11:49 ` [PATCH v5 11/12] x86/retpoline: Exclude objtool with retpoline David Woodhouse
2018-01-06 11:49 ` [PATCH v5 12/12] retpoline/modpost: Quieten MODVERSION retpoline build David Woodhouse
2018-01-07  0:10 ` [RFC PATCH 13/12] Retpoline vs. CONFIG_TRIM_UNUSED_SYMBOLS David Woodhouse
2018-01-07  8:03   ` David Woodhouse
2018-01-07 15:09     ` Lu, Hongjiu
2018-01-07 17:32       ` David Woodhouse
2018-01-07 17:57         ` Lu, Hongjiu
2018-01-07 18:18           ` Thomas Gleixner
2018-01-07 18:32             ` Lu, Hongjiu
2018-01-07 20:57               ` David Woodhouse
2018-01-07 22:16               ` David Woodhouse

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