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From: Chao Gao <chao.gao@intel.com>
To: Sergey Dyasli <sergey.dyasli@citrix.com>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
	"Ashok Raj" <ashok.raj@intel.com>, "Wei Liu" <wl@xen.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Jan Beulich" <jbeulich@suse.com>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	xen-devel@lists.xenproject.org,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Borislav Petkov" <bp@suse.de>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v9 13/15] x86/microcode: Synchronize late microcode loading
Date: Mon, 19 Aug 2019 22:49:36 +0800
Message-ID: <20190819144934.GA12597@gao-cwp> (raw)
In-Reply-To: <ea4e0bee-7151-82da-c293-fec2532f9b92@citrix.com>

On Mon, Aug 19, 2019 at 11:27:36AM +0100, Sergey Dyasli wrote:
>> +static int master_thread_fn(const struct microcode_patch *patch)
>> +{
>> +    unsigned int cpu = smp_processor_id();
>> +    int ret = 0;
>> +
>> +    while ( loading_state != LOADING_CALLIN )
>> +        cpu_relax();
>> +
>> +    cpumask_set_cpu(cpu, &cpu_callin_map);
>> +
>> +    while ( loading_state != LOADING_ENTER )
>> +        cpu_relax();
>
>If I'm reading it right, this will wait forever in case when...
>
>> +
>> +    /*
>> +     * If an error happened, control thread would set 'loading_state'
>> +     * to LOADING_EXIT. Don't perform ucode loading for this case
>> +     */
>> +    if ( loading_state == LOADING_EXIT )
>> +        return ret;

I tried to check whether there was an error here. But as you said, we
cannot reach here if 'control thread' set loading_state from LOADING_CALLIN
to LOADING_EXIT. I will do this check in the while-loop right above.

>> +
>> +    ret = microcode_ops->apply_microcode(patch);
>> +    if ( !ret )
>> +        atomic_inc(&cpu_updated);
>> +    atomic_inc(&cpu_out);
>> +
>> +    while ( loading_state != LOADING_EXIT )
>> +        cpu_relax();
>> +
>> +    return ret;
>> +}
>> +
>> +static int control_thread_fn(const struct microcode_patch *patch)
>>  {
>> -    unsigned int cpu;
>> +    unsigned int cpu = smp_processor_id(), done;
>> +    unsigned long tick;
>> +    int ret;
>>  
>> -    /* Store the patch after a successful loading */
>> -    if ( !microcode_update_cpu(patch) && patch )
>> +    /* Allow threads to call in */
>> +    loading_state = LOADING_CALLIN;
>> +    smp_mb();
>> +
>> +    cpumask_set_cpu(cpu, &cpu_callin_map);
>> +
>> +    /* Waiting for all threads calling in */
>> +    ret = wait_for_condition(wait_cpu_callin,
>> +                             (void *)(unsigned long)num_online_cpus(),
>> +                             MICROCODE_CALLIN_TIMEOUT_US);
>> +    if ( ret ) {
>> +        loading_state = LOADING_EXIT;
>> +        return ret;
>> +    }
>
>...this condition holds. Have you actually tested this case?

I didn't craft a case to verify the error-handling path. And I believe
that you are right. 

Thanks
Chao

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Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-19  1:25 [Xen-devel] [PATCH v9 00/15] improve " Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 01/15] microcode/intel: extend microcode_update_match() Chao Gao
2019-08-28 15:12   ` Jan Beulich
2019-08-29  7:15     ` Chao Gao
2019-08-29  7:14       ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 02/15] microcode/amd: fix memory leak Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 03/15] microcode/amd: distinguish old and mismatched ucode in microcode_fits() Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 04/15] microcode: introduce a global cache of ucode patch Chao Gao
2019-08-22 11:11   ` Roger Pau Monné
2019-08-28 15:21   ` Jan Beulich
2019-08-29 10:18   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 05/15] microcode: clean up microcode_resume_cpu Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 06/15] microcode: remove struct ucode_cpu_info Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 07/15] microcode: remove pointless 'cpu' parameter Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 08/15] microcode/amd: call svm_host_osvw_init() in common code Chao Gao
2019-08-22 13:08   ` Roger Pau Monné
2019-08-28 15:26   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 09/15] microcode: pass a patch pointer to apply_microcode() Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 10/15] microcode: split out apply_microcode() from cpu_request_microcode() Chao Gao
2019-08-22 13:59   ` Roger Pau Monné
2019-08-29 10:06     ` Jan Beulich
2019-08-30  3:22       ` Chao Gao
2019-08-30  7:25         ` Jan Beulich
2019-08-29 10:19   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 11/15] microcode: unify loading update during CPU resuming and AP wakeup Chao Gao
2019-08-22 14:10   ` Roger Pau Monné
2019-08-22 16:44     ` Chao Gao
2019-08-23  9:09       ` Roger Pau Monné
2019-08-29  7:37         ` Chao Gao
2019-08-29  8:16           ` Roger Pau Monné
2019-08-29 10:26           ` Jan Beulich
2019-08-29 10:29   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 12/15] microcode: reduce memory allocation and copy when creating a patch Chao Gao
2019-08-23  8:11   ` Roger Pau Monné
2019-08-26  7:03     ` Chao Gao
2019-08-26  8:11       ` Roger Pau Monné
2019-08-29 10:47   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 13/15] x86/microcode: Synchronize late microcode loading Chao Gao
2019-08-19 10:27   ` Sergey Dyasli
2019-08-19 14:49     ` Chao Gao [this message]
2019-08-29 12:06   ` Jan Beulich
2019-08-30  3:30     ` Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 14/15] microcode: remove microcode_update_lock Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 15/15] microcode: block #NMI handling when loading an ucode Chao Gao
2019-08-23  8:46   ` Sergey Dyasli
2019-08-26  8:07     ` Chao Gao
2019-08-27  4:52       ` Chao Gao
2019-08-28  8:52         ` Sergey Dyasli
2019-08-29 12:11         ` Jan Beulich
2019-08-30  6:35           ` Chao Gao
2019-09-09  5:52             ` Chao Gao
2019-09-09  6:16               ` Jan Beulich
2019-08-29 12:22   ` Jan Beulich
2019-08-30  6:33     ` Chao Gao
2019-08-30  7:30       ` Jan Beulich
2019-08-22  7:51 ` [Xen-devel] [PATCH v9 00/15] improve late microcode loading Sergey Dyasli
2019-08-22 15:39   ` Chao Gao

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