From: Steven Rostedt <rostedt@goodmis.org>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@ozlabs.org>,
linuxppc-dev@lists.ozlabs.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Anton Blanchard <anton@samba.org>,
Nicholas Piggin <npiggin@gmail.com>,
sathnaga@linux.vnet.ibm.com
Subject: Re: [PATCH 1/2] powerpc64/ftrace: Add a field in paca to disable ftrace in unsafe code paths
Date: Mon, 19 Mar 2018 10:13:44 -0400 [thread overview]
Message-ID: <20180319101344.72144f30@gandalf.local.home> (raw)
In-Reply-To: <cdbe15845a5da965878b6344f69b6ed6dbabb87b.1521449527.git.naveen.n.rao@linux.vnet.ibm.com>
On Mon, 19 Mar 2018 14:43:00 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
> diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> index 3f3e81852422..fdf702b4df25 100644
> --- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> +++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> @@ -60,6 +60,19 @@ _GLOBAL(ftrace_caller)
> mfxer r10
> mfcr r11
>
> +#ifdef CONFIG_KVM
> + lbz r3, PACA_FTRACE_DISABLED(r13)
> + cmpdi r3, 0
> + beq 1f
> + mflr r3
> + mtctr r3
> + REST_GPR(3, r1)
> + addi r1, r1, SWITCH_FRAME_SIZE
> + mtlr r0
> + bctr
> +1:
> +#endif
I wonder if we should try to move the return out of the fast path (for
cache reasons), as most of the time the above compare will be true. That
is:
#ifdef CONFIG_KVM
lbz r3, PACA_FTRACE_DISABLED(r13)
cmpdi r3, 0
bne no_trace
#endif
/* rest of ftrace_caller code */
/* after ftrace_caller... */
bctr /* jump after _mcount site */
#ifdef CONFIG_KVM
no_trace:
mflr r3
mtctr r3
REST_GPR(3, r1)
addi r1, r1, SWITCH_FRAME_SIZE
mtlr r0
bctr
#endif
-- Steve
> +
> /* Get the _mcount() call site out of LR */
> mflr r7
> /* Save it as pt_regs->nip */
next prev parent reply other threads:[~2018-03-19 14:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-19 9:12 [PATCH 0/2] Disable ftrace during kvm guest entry/exit Naveen N. Rao
2018-03-19 9:13 ` [PATCH 1/2] powerpc64/ftrace: Add a field in paca to disable ftrace in unsafe code paths Naveen N. Rao
2018-03-19 10:40 ` Nicholas Piggin
2018-03-19 18:53 ` Naveen N. Rao
2018-03-19 22:34 ` Michael Ellerman
2018-03-20 0:05 ` Nicholas Piggin
2018-03-20 11:02 ` Naveen N. Rao
2018-03-19 14:13 ` Steven Rostedt [this message]
2018-03-19 18:54 ` Naveen N. Rao
2018-03-19 9:13 ` [PATCH 2/2] powerpc64/ftrace: Disable ftrace during kvm guest entry/exit Naveen N. Rao
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