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From: mark gross <mgross@linux.intel.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH 2/3] V5 more sampling fun 2
Date: Wed, 8 Apr 2020 13:26:52 -0700	[thread overview]
Message-ID: <20200408202652.GA136636@mtg-dev.jf.intel.com> (raw)
In-Reply-To: <20200407123955.ejjkigwkgfm2v4dt@treble>

On Tue, Apr 07, 2020 at 07:39:55AM -0500, speck for Josh Poimboeuf wrote:
> On Mon, Apr 06, 2020 at 05:34:56PM -0700, speck for mark gross wrote:
> > On Mon, Apr 06, 2020 at 05:07:14PM -0500, speck for Josh Poimboeuf 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) {
> > > > +		if (!boot_cpu_has(X86_FEATURE_RTM))
> > > > +			srbds_mitigation = SRBDS_NOT_AFFECTED_TSX_OFF;
> > > > +	}
> > > 
> > > A 'goto out' would be helpful here; then the TSX_OFF checks below aren't
> > > needed and the flow is simplified.
> > a goto out would mess up the hypervisor check but, I'll add the goto for the
> > mid function returns that set the srbds_mitigation value.
> 
> Just to clarify, I was thinking something like:
> 
> 	ia32_cap = x86_read_arch_cap_msr();
> 	if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM)) {
> 		srbds_mitigation = SRBDS_NOT_AFFECTED_TSX_OFF;
> 		goto out;
> 	}
> 
> As far as I can tell, that doesn't mess up the hypervisor check, since
> it only sets SRBDS_HYPERVISOR if TSX_OFF isn't set.
after looking again I agree and using the goto allows simplification of the
following if block.

> > 
> > > > +
> > > > +	if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
> > > > +		if (srbds_mitigation != SRBDS_NOT_AFFECTED_TSX_OFF)
> > > > +			srbds_mitigation = SRBDS_HYPERVISOR;
> > > > +		return;
with your goto out aboe I can simplify this if block by removing the nested if.

Thanks!

--mark

> > > > +	}
> > > > +
> > > > +/*
> > > > + * List affected CPU's for issues that cannot be enumerated.
> > > > + */
> > > 
> > > I don't understand the comment, SRBDS seems to be enumerated above.
> > hmm, how about I remove the comment? 
> 
> Sounds good to me.
> 
> -- 
> Josh

  reply	other threads:[~2020-04-08 20:27 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-06 17:52 [MODERATED] [PATCH 0/3] V5 more sampling fun 0 mark gross
2020-01-16 22:16 ` [MODERATED] [PATCH 2/3] V5 more sampling fun 2 mark gross
2020-01-30 19:12 ` [MODERATED] [PATCH 3/3] V5 more sampling fun 3 mark gross
2020-03-17  0:56 ` [MODERATED] [PATCH 1/3] V5 more sampling fun 1 mark gross
     [not found] ` <5e8b7166.1c69fb81.4c99a.3619SMTPIN_ADDED_BROKEN@mx.google.com>
2020-04-06 18:31   ` [MODERATED] " Kees Cook
     [not found] ` <5e8b71d8.1c69fb81.64075.43abSMTPIN_ADDED_BROKEN@mx.google.com>
2020-04-06 18:34   ` [MODERATED] Re: [PATCH 2/3] V5 more sampling fun 2 Kees Cook
2020-04-06 18:37     ` Greg KH
2020-04-06 20:56       ` mark gross
2020-04-06 22:14       ` Luck, Tony
2020-04-07  7:51         ` Greg KH
2020-04-06 18:52     ` mark gross
     [not found] ` <5e8b71af.1c69fb81.d8b8.ac6bSMTPIN_ADDED_BROKEN@mx.google.com>
2020-04-06 18:34   ` [MODERATED] Re: [PATCH 3/3] V5 more sampling fun 3 Kees Cook
2020-04-06 22:07 ` [MODERATED] Re: [PATCH 2/3] V5 more sampling fun 2 Josh Poimboeuf
2020-04-07  0:34   ` mark gross
2020-04-07 12:39     ` Josh Poimboeuf
2020-04-08 20:26       ` mark gross [this message]
2020-04-08 22:14   ` mark gross
2020-04-08 22:58     ` mark gross
2020-04-07 15:17 ` Thomas Gleixner
2020-04-08 20:33   ` [MODERATED] " mark gross
2020-04-08 23:21     ` Thomas Gleixner

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