From: Breno Leitao <leitao@debian.org>
To: Anton Blanchard <anton@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org, Gustavo Romero <gusbromero@gmail.com>
Subject: Re: [PATCH] powerpc/kernel: improve FP and vector registers restoration
Date: Sat, 3 Jun 2017 19:42:14 -0300 [thread overview]
Message-ID: <20170603224213.7pf3vdltypx3uwom@gmail.com> (raw)
In-Reply-To: <20170603080411.59df057d@kryten>
Hi Anton,
On Sat, Jun 03, 2017 at 08:04:11AM +1000, Anton Blanchard wrote:
> Hi Breno,
>
> > Currently tsk->thread->load_vec and load_fp are not initialized
> > during a task creation, which set garbage to these variables
> > (non-zero value).
>
> Nice catch! It seems like we should zero load_tm too though?
Yes, it seems we need to zero load_tm also, since it does not seem to be
zeroed anywhere else.
But I did some tests, and load_tm is always zero after start_thread()
is being called.
In fact, start_thread() is being called and pt_regs->load_tm is already
zero since the function start.
I also wrote a SystemTap script[1] to investigate it better, and I've
never seen a single load_tm != 0 in a my machine. I tested on both
POWER8 bare metal and KVM guests. (load_vec and load_fp happened to have
garbage all the time)
Any idea if this is just occasional event, or, if there is someone
zeroing it in an obscure code?
[1] https://github.com/leitao/htm_torture/blob/master/systemtap/load_tm_at_start_thread.stap
next prev parent reply other threads:[~2017-06-03 22:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-02 21:43 [PATCH] powerpc/kernel: improve FP and vector registers restoration Breno Leitao
2017-06-02 22:04 ` Anton Blanchard
2017-06-03 22:42 ` Breno Leitao [this message]
2017-06-04 1:38 ` Anton Blanchard
2017-06-04 14:34 ` Breno Leitao
2017-06-05 5:59 ` Michael Ellerman
2017-06-08 4:05 ` Michael Ellerman
-- strict thread matches above, loose matches on Subject: below --
2017-06-02 20:56 [PATCH] " Breno Leitao
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