[PATCH] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[PATCH] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Srivatsa S. Bhat]

Requesting the microcode from userspace *every time* when onlining CPUs
(during a CPU hotplug operation) is unnecessary.

So, this patch ensures that once the kernel gets the microcode after booting,
it is not freed nor invalidated when a CPU goes offline, so that it can be
reused when that CPU comes back online, without requesting userspace for it
again. As a result, the CPU hotplug operations become faster as well.

Tested-by: Borislav Petkov <bp@amd64.org>
Acked-by: Borislav Petkov <bp@amd64.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/x86/kernel/microcode_core.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index f924280..3fd0189 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -483,7 +483,13 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
 		sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
 		pr_debug("CPU%d removed\n", cpu);
 		break;
-	case CPU_DEAD:
+
+	/* When a CPU goes offline, don't free up or invalidate the copy of
+	 * the microcode in kernel memory, so that we can reuse it when the
+	 * CPU comes back online without unnecessarily requesting the userspace
+	 * for it again.
+	 */
+
 	case CPU_UP_CANCELED_FROZEN:
 		/* The CPU refused to come up during a system resume */
 		microcode_fini_cpu(cpu);

Re: [PATCH] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Borislav Petkov]

On Sat, Oct 08, 2011 at 04:47:53PM -0400, Srivatsa S. Bhat wrote:
> Requesting the microcode from userspace *every time* when onlining CPUs
> (during a CPU hotplug operation) is unnecessary.
> 
> So, this patch ensures that once the kernel gets the microcode after booting,
> it is not freed nor invalidated when a CPU goes offline, so that it can be
> reused when that CPU comes back online, without requesting userspace for it
> again. As a result, the CPU hotplug operations become faster as well.
> 
> Tested-by: Borislav Petkov <bp@amd64.org>
> Acked-by: Borislav Petkov <bp@amd64.org>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Good, thanks. Just a minor nitpick below.

> ---
> 
>  arch/x86/kernel/microcode_core.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
> index f924280..3fd0189 100644
> --- a/arch/x86/kernel/microcode_core.c
> +++ b/arch/x86/kernel/microcode_core.c
> @@ -483,7 +483,13 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
>  		sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
>  		pr_debug("CPU%d removed\n", cpu);
>  		break;
> -	case CPU_DEAD:
> +
> +	/* When a CPU goes offline, don't free up or invalidate the copy of
> +	 * the microcode in kernel memory, so that we can reuse it when the
> +	 * CPU comes back online without unnecessarily requesting the userspace
> +	 * for it again.
> +	 */
> +

Kernel comment style is in this format:

/*
 * Blabla
 * blublu
 */

@Ingo, can you please adjust it in-flight when applying?

Thanks.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551

Re: [PATCH] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Srivatsa S. Bhat]

On 10/09/2011 04:57 PM, Borislav Petkov wrote:
> On Sat, Oct 08, 2011 at 04:47:53PM -0400, Srivatsa S. Bhat wrote:
>> Requesting the microcode from userspace *every time* when onlining CPUs
>> (during a CPU hotplug operation) is unnecessary.
>>
>> So, this patch ensures that once the kernel gets the microcode after booting,
>> it is not freed nor invalidated when a CPU goes offline, so that it can be
>> reused when that CPU comes back online, without requesting userspace for it
>> again. As a result, the CPU hotplug operations become faster as well.
>>
>> Tested-by: Borislav Petkov <bp@amd64.org>
>> Acked-by: Borislav Petkov <bp@amd64.org>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> 
> Good, thanks. Just a minor nitpick below.
> 
>> ---
>>
>>  arch/x86/kernel/microcode_core.c |    8 +++++++-
>>  1 files changed, 7 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
>> index f924280..3fd0189 100644
>> --- a/arch/x86/kernel/microcode_core.c
>> +++ b/arch/x86/kernel/microcode_core.c
>> @@ -483,7 +483,13 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
>>  		sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
>>  		pr_debug("CPU%d removed\n", cpu);
>>  		break;
>> -	case CPU_DEAD:
>> +
>> +	/* When a CPU goes offline, don't free up or invalidate the copy of
>> +	 * the microcode in kernel memory, so that we can reuse it when the
>> +	 * CPU comes back online without unnecessarily requesting the userspace
>> +	 * for it again.
>> +	 */
>> +
> 
> Kernel comment style is in this format:
> 
> /*
>  * Blabla
>  * blublu
>  */
> 
Oh, ok.. Thank you for pointing it out.

> @Ingo, can you please adjust it in-flight when applying?

I'll post the patch with the correct comment style, if that would make
things easier.
-- 
Regards,
Srivatsa S. Bhat  <srivatsa.bhat@linux.vnet.ibm.com>
Linux Technology Center,
IBM India Systems and Technology Lab

[PATCH RESEND] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Srivatsa S. Bhat]

Requesting the microcode from userspace *every time* when onlining CPUs
(during a CPU hotplug operation) is unnecessary.

So, this patch ensures that once the kernel gets the microcode after booting,
it is not freed nor invalidated when a CPU goes offline, so that it can be
reused when that CPU comes back online, without requesting userspace for it
again. As a result, the CPU hotplug operations become faster as well.

Tested-by: Borislav Petkov <bp@amd64.org>
Acked-by: Borislav Petkov <bp@amd64.org>

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/x86/kernel/microcode_core.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index f924280..33c8a67 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -483,7 +483,14 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
 		sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
 		pr_debug("CPU%d removed\n", cpu);
 		break;
-	case CPU_DEAD:
+
+	/*
+	 * When a CPU goes offline, don't free up or invalidate the copy of
+	 * the microcode in kernel memory, so that we can reuse it when the
+	 * CPU comes back online without unnecessarily requesting the userspace
+	 * for it again.
+	 */
+
 	case CPU_UP_CANCELED_FROZEN:
 		/* The CPU refused to come up during a system resume */
 		microcode_fini_cpu(cpu);

Re: [PATCH RESEND] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Rafael J. Wysocki]

On Sunday, October 09, 2011, Srivatsa S. Bhat wrote:
> Requesting the microcode from userspace *every time* when onlining CPUs
> (during a CPU hotplug operation) is unnecessary.
> 
> So, this patch ensures that once the kernel gets the microcode after booting,
> it is not freed nor invalidated when a CPU goes offline, so that it can be
> reused when that CPU comes back online, without requesting userspace for it
> again. As a result, the CPU hotplug operations become faster as well.
> 
> Tested-by: Borislav Petkov <bp@amd64.org>
> Acked-by: Borislav Petkov <bp@amd64.org>
> 
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Fine by me.  I wonder who should take this?

Rafael


> ---
> 
>  arch/x86/kernel/microcode_core.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
> index f924280..33c8a67 100644
> --- a/arch/x86/kernel/microcode_core.c
> +++ b/arch/x86/kernel/microcode_core.c
> @@ -483,7 +483,14 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
>  		sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
>  		pr_debug("CPU%d removed\n", cpu);
>  		break;
> -	case CPU_DEAD:
> +
> +	/*
> +	 * When a CPU goes offline, don't free up or invalidate the copy of
> +	 * the microcode in kernel memory, so that we can reuse it when the
> +	 * CPU comes back online without unnecessarily requesting the userspace
> +	 * for it again.
> +	 */
> +
>  	case CPU_UP_CANCELED_FROZEN:
>  		/* The CPU refused to come up during a system resume */
>  		microcode_fini_cpu(cpu);
> 
> 
> 
> 

Re: [PATCH RESEND] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Borislav Petkov]

On Mon, Oct 10, 2011 at 04:58:02PM -0400, Rafael J. Wysocki wrote:
> On Sunday, October 09, 2011, Srivatsa S. Bhat wrote:
> > Requesting the microcode from userspace *every time* when onlining CPUs
> > (during a CPU hotplug operation) is unnecessary.
> > 
> > So, this patch ensures that once the kernel gets the microcode after booting,
> > it is not freed nor invalidated when a CPU goes offline, so that it can be
> > reused when that CPU comes back online, without requesting userspace for it
> > again. As a result, the CPU hotplug operations become faster as well.
> > 
> > Tested-by: Borislav Petkov <bp@amd64.org>
> > Acked-by: Borislav Petkov <bp@amd64.org>
> > 
> > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> 
> Fine by me.  I wonder who should take this?

Ingo, most probably. ucode stuff goes in through -tip.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551

Re: [PATCH RESEND] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Rafael J. Wysocki]

On Monday, October 10, 2011, Borislav Petkov wrote:
> On Mon, Oct 10, 2011 at 04:58:02PM -0400, Rafael J. Wysocki wrote:
> > On Sunday, October 09, 2011, Srivatsa S. Bhat wrote:
> > > Requesting the microcode from userspace *every time* when onlining CPUs
> > > (during a CPU hotplug operation) is unnecessary.
> > > 
> > > So, this patch ensures that once the kernel gets the microcode after booting,
> > > it is not freed nor invalidated when a CPU goes offline, so that it can be
> > > reused when that CPU comes back online, without requesting userspace for it
> > > again. As a result, the CPU hotplug operations become faster as well.
> > > 
> > > Tested-by: Borislav Petkov <bp@amd64.org>
> > > Acked-by: Borislav Petkov <bp@amd64.org>
> > > 
> > > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> > 
> > Fine by me.  I wonder who should take this?
> 
> Ingo, most probably. ucode stuff goes in through -tip.

OK, so

Acked-by: Rafael J. Wysocki <rjw@sisk.pl>

Thanks,
Rafael

Re: [PATCH RESEND] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily

[Andreas Herrmann]

On Sun, Oct 09, 2011 at 03:42:00PM -0400, Srivatsa S. Bhat wrote:
> Requesting the microcode from userspace *every time* when onlining CPUs
> (during a CPU hotplug operation) is unnecessary.
> 
> So, this patch ensures that once the kernel gets the microcode after booting,
> it is not freed nor invalidated when a CPU goes offline, so that it can be
> reused when that CPU comes back online, without requesting userspace for it
> again. As a result, the CPU hotplug operations become faster as well.
> 
> Tested-by: Borislav Petkov <bp@amd64.org>
> Acked-by: Borislav Petkov <bp@amd64.org>
> 
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>


Thanks,

Andreas

>  arch/x86/kernel/microcode_core.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
> index f924280..33c8a67 100644
> --- a/arch/x86/kernel/microcode_core.c
> +++ b/arch/x86/kernel/microcode_core.c
> @@ -483,7 +483,14 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
>  		sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
>  		pr_debug("CPU%d removed\n", cpu);
>  		break;
> -	case CPU_DEAD:
> +
> +	/*
> +	 * When a CPU goes offline, don't free up or invalidate the copy of
> +	 * the microcode in kernel memory, so that we can reuse it when the
> +	 * CPU comes back online without unnecessarily requesting the userspace
> +	 * for it again.
> +	 */
> +
>  	case CPU_UP_CANCELED_FROZEN:
>  		/* The CPU refused to come up during a system resume */
>  		microcode_fini_cpu(cpu);
> 
> 
>