From: Waiman Long <longman@redhat.com>
To: "Tada, Kenta (Sony)" <Kenta.Tada@sony.com>,
"x86@kernel.org" <x86@kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>, "hpa@zytor.com" <hpa@zytor.com>,
"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"tony.luck@intel.com" <tony.luck@intel.com>,
"pawan.kumar.gupta@linux.intel.com"
<pawan.kumar.gupta@linux.intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/speculation: Check whether speculation is force disabled
Date: Wed, 3 Jun 2020 11:39:38 -0400 [thread overview]
Message-ID: <d0356d0a-83dd-f3ae-c0ba-82089976c014@redhat.com> (raw)
In-Reply-To: <TYXPR01MB150318D484EE220452A5085AF5880@TYXPR01MB1503.jpnprd01.prod.outlook.com>
On 6/3/20 3:12 AM, Tada, Kenta (Sony) wrote:
> Once PR_SPEC_FORCE_DISABLE is set, users cannot set PR_SPEC_ENABLE.
> This commit checks whether PR_SPEC_FORCE_DISABLE was previously set.
>
> Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
> ---
> arch/x86/kernel/cpu/bugs.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index ed54b3b21c39..678ace157035 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -1173,6 +1173,9 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
> if (spectre_v2_user == SPECTRE_V2_USER_STRICT ||
> spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED)
> return -EPERM;
> + /* If speculation is force disabled, enable is not allowed */
> + if (task_spec_ib_force_disable(task))
> + return -EPERM;
> task_clear_spec_ib_disable(task);
> task_update_spec_tif(task);
> break;
There is a comment up a few lines about this:
/*
* Indirect branch speculation is always allowed when
* mitigation is force disabled.
*/
It conflicts with your new code. We can have an argument on whether IB
should follow how SSB is being handled. Before that is settled,
Nacked-by: Waiman Long <longman@redhat.com>
next prev parent reply other threads:[~2020-06-03 15:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 7:12 [PATCH] x86/speculation: Check whether speculation is force disabled Tada, Kenta (Sony)
2020-06-03 15:39 ` Waiman Long [this message]
2020-06-04 7:29 ` Tada, Kenta (Sony)
2020-06-04 16:10 ` Waiman Long
2020-06-05 12:07 ` Tada, Kenta (Sony)
2020-06-17 0:15 ` Tada, Kenta (Sony)
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