linux-kernel - Re: [PATCH v5 07/12] x86: remove the syscall

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Date:   Sun, 28 Jan 2018 07:22:26 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Dan Williams <dan.j.williams@...el.com>, tglx@...utronix.de,
        linux-arch@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        gregkh@...uxfoundation.org, x86@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, torvalds@...ux-foundation.org,
        alan@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 07/12] x86: remove the syscall_64 fast-path




> On Jan 28, 2018, at 1:29 AM, Ingo Molnar <mingo@...nel.org> wrote:
> 
> 
> * Dan Williams <dan.j.williams@...el.com> wrote:
> 
>> Quoting Linus:
>> 
>>  "Honestly, I'd rather get rid of the fast-path entirely. Compared to
>>   all the PTI mess, it's not even noticeable.
>> 
>>   And if we ever get CPU's that have this all fixed, we can re-visit
>>   introducing the fastpath. But this is all very messy and it doesn't
>>   seem worth it right now.
>> 
>>   If we get rid of the fastpath, we can lay out the slow path slightly
>>   better, and get rid of some of those jump-overs. And we'd get rid of
>>   the ptregs hooks entirely.
>> 
>>   So we can try to make the "slow" path better while at it, but I
>>   really don't think it matters much now in the post-PTI era. Sadly."
> 
> Please fix the title to have the proper prefix and to reference the function that 
> is actually modified by the patch, i.e. something like:
> 
> s/ x86: remove the syscall_64 fast-path
> / x86/entry/64: Remove the entry_SYSCALL_64() fast-path
> 
> With the title fixed:
> 
> Reviewed-by: Ingo Molnar <mingo@...nel.org>

I have a very similar but not quite identical version I'll send out shortly.  The difference is that I fixed the silly prologue.

> 
> Thanks,
> 
>    Ingo