From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
konrad.wilk@oracle.com, x86@kernel.org, dwmw@amazon.co.uk,
tglx@linutronix.de,
Srinivas REDDY Eeda <srinivas.eeda@oracle.com>,
bp@suse.de, hpa@zytor.com, dhaval.giani@oracle.com
Subject: Re: [PATCH] x86/speculation: Use AMD specific retpoline for inline asm on AMD
Date: Tue, 18 Sep 2018 22:41:10 +0800 [thread overview]
Message-ID: <9074a680-ad3d-e222-5b19-eb13fd1d4e28@oracle.com> (raw)
In-Reply-To: <20180918130058.GM24106@hirez.programming.kicks-ass.net>
On 2018/9/18 21:00, Peter Zijlstra wrote:
> On Tue, Sep 18, 2018 at 08:04:44PM +0800, Zhenzhong Duan wrote:
>> On 2018/9/18 18:59, Peter Zijlstra wrote:
>>> On Tue, Sep 18, 2018 at 06:31:07PM +0800, Zhenzhong Duan wrote:
>>>> On 2018/9/18 17:50, Peter Zijlstra wrote:
>>>>> On Mon, Sep 17, 2018 at 10:17:30PM -0700, Zhenzhong Duan wrote:
>>>>>> -#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE)
>>>>>> +#elif defined(CONFIG_RETPOLINE)
>>>>> This doesn't make any sense..
>>>> This change is used for x86_64 to have minimal Retpoline support when
>>>> CONFIG_RETPOLINE is defined but RETPOLINE isn't defined, or I missed
>>>> something?
>>> No it doesn't.
>>>
>>> #if defined(X86_64) && defined(RETPOLINE)
>>>
>>> /* x86_64 retpoline goes here */
>>>
>>> #elif defined(RETPOLINE)
>>>
>>> /* !x86_64 retpoline goes here */
>>>
>>> #else
>>>
>>> /* !retpoline goes here
>>>
>>> #endif
>> Sorry, but I am confused.
>> So where is 'if defined(x86_64) && !defined(RETPOLINE) &&
>> defined(CONFIG_RETPOLINE)' go?
> Argh, CONFIG_RETPOLINE vs RETPOLINE :/
>
> The thing is, the one you modify has a comment on that explains why it
> is i386 only. CET and retpolines don't like one another much.
>
> And the x86_64 version uses %V which requires new GCC.
>
> So I'm all for fixing the RETPOLINE_AMD thing, but at this point nobody
> should use the minimal stuff, that's just delusional.
>
Clear, thanks for your explanation.
Zhenzhong
prev parent reply other threads:[~2018-09-18 14:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-18 5:17 [PATCH] x86/speculation: Use AMD specific retpoline for inline asm on AMD Zhenzhong Duan
2018-09-18 9:50 ` Peter Zijlstra
2018-09-18 10:31 ` Zhenzhong Duan
2018-09-18 10:59 ` Peter Zijlstra
2018-09-18 12:04 ` Zhenzhong Duan
2018-09-18 13:00 ` Peter Zijlstra
2018-09-18 13:03 ` Peter Zijlstra
2018-09-18 13:32 ` David Woodhouse
2018-09-18 14:41 ` Zhenzhong Duan [this message]
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