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From: mark gross <mgross@linux.intel.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH 3/4] V7 more sampling fun 3
Date: Tue, 14 Apr 2020 13:03:12 -0700	[thread overview]
Message-ID: <20200414200312.GB29751@mtg-dev.jf.intel.com> (raw)
In-Reply-To: <87h7xmniid.fsf@nanos.tec.linutronix.de>

On Tue, Apr 14, 2020 at 06:23:38PM +0200, speck for Thomas Gleixner wrote:
> Mark,
> 
> speck for mark gross <speck@linutronix.de> writes:
> > On Thu, Jan 16, 2020 at 02:16:07PM -0800, speck for mark gross wrote:
> >> +	/*
> >> +	 * Check to see if this is one of the MDS_NO systems supporting
> >> +	 * TSX that are only exposed to SRBDS when TSX is enabled.
> >> +	 */
> >> +	ia32_cap = x86_read_arch_cap_msr();
> >> +	if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM)) {
> >> +		srbds_mitigation = SRBDS_MITIGATION_NOT_AFFECTED_TSX_OFF;
> >> +		goto out;
> >> +	}
> >> +
> >> +	if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
> >> +		srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR;
> >> +		goto out;
> >> +	}
> >> +
> >> +	if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL)) {
> >> +		srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED;
> >> +		goto out;
> >> +	}
> >> +
> >> +	if (cpu_mitigations_off() || srbds_off) {
> >> +		if (srbds_mitigation != SRBDS_MITIGATION_NOT_AFFECTED_TSX_OFF)
> >> +			srbds_mitigation = SRBDS_MITIGATION_OFF;
> >> +	}
> >> +out:
> > The test for cpu_mitigations_off or srbds off needs to be after out:
> > Otherwise when TSX is off and srbds=off will report the wrong answer.
> 
> If the CPU has SRBDS_IF_TSX and TSX is disabled then the correct
> answer is: Not affected (TSX off)
correct.

> That's what we do with other issues as well. If the CPU is not affected
> then we print this even with mitigation disabled (all or particular).

That is what I'm working toward.  Now that I look at the code the right answer
is to not move the out: lable and nuke the nested if int eht srbds_off branch.
That is whats wrong.

That said I plan to us your if/else construct on the next version and forget
about the goto's.

--mark

  reply	other threads:[~2020-04-14 20:03 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-13 18:10 [MODERATED] [PATCH 0/4] V7 more sampling fun 0 mark gross
2020-01-16 22:16 ` [MODERATED] [PATCH 3/4] V7 more sampling fun 3 mark gross
2020-01-30 19:12 ` [MODERATED] [PATCH 4/4] V7 more sampling fun 4 mark gross
2020-03-17  0:56 ` [MODERATED] [PATCH 2/4] V7 more sampling fun 2 mark gross
2020-03-17  0:56 ` [MODERATED] [PATCH 1/4] V7 more sampling fun 1 mark gross
2020-04-14  3:48 ` [MODERATED] Re: [PATCH 3/4] V7 more sampling fun 3 mark gross
2020-04-14 16:23   ` Thomas Gleixner
2020-04-14 20:03     ` mark gross [this message]
2020-04-14 10:58 ` Thomas Gleixner
2020-04-14 16:43   ` [MODERATED] " mark gross
2020-04-14 20:02 ` Josh Poimboeuf
2020-04-14 21:03   ` mark gross
2020-04-14 21:23     ` Josh Poimboeuf
2020-04-14 21:53       ` mark gross
2020-04-14 20:05 ` Josh Poimboeuf
2020-04-14 21:59   ` mark gross
2020-04-14 22:46     ` Josh Poimboeuf
2020-04-15 20:59       ` mark gross
2020-04-15 12:58     ` Thomas Gleixner
2020-04-15 22:21       ` [MODERATED] " mark gross
2020-04-15 17:51 ` [MODERATED] Re: [PATCH 1/4] V7 more sampling fun 1 Borislav Petkov
2020-04-15 23:58   ` mark gross

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