linux-kernel - Re: Do the x86 kernel entry points need an xabort on TSX cpus?

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Message-ID: <CALCETrVHpfW5=paX8XjGNBg3Q7sjeLptMBG6bW=iQpXk0Uo+PA@mail.gmail.com>
Date:	Fri, 10 Feb 2012 09:24:01 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: Do the x86 kernel entry points need an xabort on TSX cpus?

On Fri, Feb 10, 2012 at 9:18 AM, H. Peter Anvin <hpa@...ux.intel.com> wrote:
> On 02/09/2012 11:40 PM, Andy Lutomirski wrote:
>>
>> [...]
>>
>>  - Ring transitions: SYSENTER, SYSCALL, SYSEXIT, and SYSRET.
>>
>> I suspect that many bits of the kernel expect that things they do
>> won't unhappen.  For example, it could be fun to do:
>>
>
> That's why entering the kernel will cause an abort.  In other words, you
> will ALWAYS abort when you do a read(), and you will never reach your
> _xabort().

Is that architecturally guaranteed?  (My manual suggests that it's
specifically *not* guaranteed, which is surprising.)

--Andy
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