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From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Wei Liu <wei.liu2@citrix.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	Chao Gao <chao.gao@intel.com>
Subject: Re: [PATCH v5 8/8] microcode: update microcode on cores in parallel
Date: Tue, 12 Feb 2019 14:25:07 +0100	[thread overview]
Message-ID: <20190212132507.mwp4yyf22oslc7d4@mac> (raw)
In-Reply-To: <5C62C15D0200007800215E2E@prv1-mh.provo.novell.com>

On Tue, Feb 12, 2019 at 05:51:41AM -0700, Jan Beulich wrote:
> >>> On 28.01.19 at 08:06, <chao.gao@intel.com> wrote:
> > @@ -314,9 +310,7 @@ static int apply_microcode(unsigned int cpu)
> >  
> >      mc_intel = patch->data;
> >      BUG_ON(!mc_intel);
> > -
> > -    /* serialize access to the physical write to MSR 0x79 */
> > -    spin_lock_irqsave(&microcode_update_lock, flags);
> > +    BUG_ON(local_irq_is_enabled());
> >  
> >      /* write microcode via MSR 0x79 */
> >      wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc_intel->bits);
> > @@ -329,7 +323,6 @@ static int apply_microcode(unsigned int cpu)
> >      rdmsrl(MSR_IA32_UCODE_REV, msr_content);
> >      val[1] = (uint32_t)(msr_content >> 32);
> >  
> > -    spin_unlock_irqrestore(&microcode_update_lock, flags);
> >      if ( val[1] != mc_intel->hdr.rev )
> >      {
> >          printk(KERN_ERR "microcode: CPU%d update from revision "
> 
> Am I understanding right that you now rely on upper layers in the
> call tree to avoid calling into here in parallel for two hyperthreads
> of the same core? I can't see how you avoid this situation during
> AP bringup, for example. Did I overlook anything in this regard?

IIRC microcode update is done in the serialized part of AP bringup,
before the call to smp_callin, which guarantees serialization.

Roger.

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  reply	other threads:[~2019-02-12 13:25 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-28  7:06 [PATCH v5 0/8] improve late microcode loading Chao Gao
2019-01-28  7:06 ` [PATCH v5 1/8] microcode/intel: remove redundent check against ucode size Chao Gao
2019-01-28 16:40   ` Roger Pau Monné
2019-01-29 10:26   ` Jan Beulich
2019-01-29 13:34     ` Chao Gao
2019-01-28  7:06 ` [PATCH v5 2/8] microcode/intel: extend microcode_update_match() Chao Gao
2019-01-28 16:55   ` Roger Pau Monné
2019-01-28 17:00     ` Jan Beulich
2019-01-29 10:41   ` Jan Beulich
2019-01-29 13:52     ` Chao Gao
2019-01-28  7:06 ` [PATCH v5 3/8] microcode: introduce the global microcode cache Chao Gao
2019-01-28 17:39   ` Roger Pau Monné
2019-01-29  4:41     ` Chao Gao
2019-01-29  8:56       ` Roger Pau Monné
2019-02-08 11:41   ` Jan Beulich
2019-02-11  3:59     ` Chao Gao
2019-02-11 13:16       ` Jan Beulich
2019-01-28  7:06 ` [PATCH v5 4/8] microcode: delete 'mc' field from struct ucode_cpu_info Chao Gao
2019-01-29  9:25   ` Roger Pau Monné
2019-01-29 13:27     ` Chao Gao
2019-01-28  7:06 ` [PATCH v5 5/8] microcode: split out apply_microcode() from cpu_request_microcode() Chao Gao
2019-01-29  9:58   ` Roger Pau Monné
2019-01-29 12:47     ` Chao Gao
2019-02-08 15:58   ` Jan Beulich
2019-01-28  7:06 ` [PATCH v5 6/8] microcode: delete microcode pointer and size from microcode_info Chao Gao
2019-01-29 10:10   ` Roger Pau Monné
2019-01-29 14:11     ` Chao Gao
2019-01-28  7:06 ` [PATCH v5 7/8] x86/microcode: Synchronize late microcode loading Chao Gao
2019-01-29 10:37   ` Roger Pau Monné
2019-01-29 10:45     ` Jan Beulich
2019-01-30 13:44     ` Chao Gao
2019-02-08 16:29   ` Jan Beulich
2019-02-11  5:40     ` Chao Gao
2019-02-11 13:23       ` Jan Beulich
2019-02-11 13:35         ` Juergen Gross
2019-02-11 15:28           ` Raj, Ashok
2019-02-11 16:49           ` Jan Beulich
2019-01-28  7:06 ` [PATCH v5 8/8] microcode: update microcode on cores in parallel Chao Gao
2019-01-29 11:27   ` Roger Pau Monné
2019-01-30 13:36     ` Chao Gao
2019-02-12 12:51   ` Jan Beulich
2019-02-12 13:25     ` Roger Pau Monné [this message]
2019-02-12 13:55       ` Jan Beulich
2019-02-13  2:30         ` Chao Gao
2019-02-13  7:20           ` Jan Beulich
2019-02-13  8:50             ` Chao Gao
2019-02-13 10:05               ` Jan Beulich
2019-01-29 11:31 ` [PATCH v5 0/8] improve late microcode loading Roger Pau Monné
2019-01-29 12:11   ` Chao Gao
2019-01-29 14:17     ` Roger Pau Monné

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