Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads

[Ingo Molnar]

* Raj, Ashok  wrote:

> Hi Ingo
> 
> On Sat, Feb 17, 2018 at 08:50:53AM +0100, Ingo Molnar wrote:
> > 
> > Also, more fundamentally, during microcode early testing, isn't it possible 
> > for 
> > internal iterations of the microcode to have the same revision, but be 
> > different?
> 
> Atleast we don't do that here. Such debug microcode isn't OS loadable. 
> Anything that comes out ready for OS loading, the version will keep moving.

Ok.

Thanks,

Ingo

Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads

[Ingo Molnar]

* Raj, Ashok  wrote:

> Hi Ingo
> 
> On Sat, Feb 17, 2018 at 08:50:53AM +0100, Ingo Molnar wrote:
> > 
> > Also, more fundamentally, during microcode early testing, isn't it possible 
> > for 
> > internal iterations of the microcode to have the same revision, but be 
> > different?
> 
> Atleast we don't do that here. Such debug microcode isn't OS loadable. 
> Anything that comes out ready for OS loading, the version will keep moving.

Ok.

Thanks,

Ingo

Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads

[Raj, Ashok]

Hi Ingo

On Sat, Feb 17, 2018 at 08:50:53AM +0100, Ingo Molnar wrote:
> 
> Also, more fundamentally, during microcode early testing, isn't it possible 
> for 
> internal iterations of the microcode to have the same revision, but be 
> different?

Atleast we don't do that here. Such debug microcode isn't OS loadable. 
Anything that comes out ready for OS loading, the version will keep moving.

> This patch would prevent re-loading it - for a seemingly minimal benefit.

Cheers,
Ashok

Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads

[Raj, Ashok]

Hi Ingo

On Sat, Feb 17, 2018 at 08:50:53AM +0100, Ingo Molnar wrote:
> 
> Also, more fundamentally, during microcode early testing, isn't it possible 
> for 
> internal iterations of the microcode to have the same revision, but be 
> different?

Atleast we don't do that here. Such debug microcode isn't OS loadable. 
Anything that comes out ready for OS loading, the version will keep moving.

> This patch would prevent re-loading it - for a seemingly minimal benefit.

Cheers,
Ashok

Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads

[Ingo Molnar]

* Ashok Raj  wrote:

> After updating microcode on one of the threads in the core, the
> thread sibling automatically gets the update since the microcode
> resources are shared. Check the ucode revision on the cpu before
> performing a ucode update.

s/cpu/CPU

> 
> Signed-off-by: Ashok Raj 
> Cc: X86 ML 
> Cc: LKML 
> ---
>  arch/x86/kernel/cpu/microcode/intel.c | 16 +---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c 
> b/arch/x86/kernel/cpu/microcode/intel.c
> index 09b95a7..036d1db 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -776,7 +776,7 @@ static enum ucode_state apply_microcode_intel(int cpu)
>  {
>   struct microcode_intel *mc;
>   struct ucode_cpu_info *uci;
> - struct cpuinfo_x86 *c;
> + struct cpuinfo_x86 *c = _data(cpu);
>   static int prev_rev;
>   u32 rev;
>  
> @@ -793,6 +793,18 @@ static enum ucode_state apply_microcode_intel(int cpu)
>   return UCODE_NFOUND;
>   }
>  
> + rev = intel_get_microcode_revision();
> + /*
> +  * Its possible the microcode got udpated
> +  * because its sibling update was done earlier.
> +  * Skip the udpate in that case.
> +  */
> + if (rev >= mc->hdr.rev) {
> + uci->cpu_sig.rev = rev;
> + c->microcode = rev;
> + return UCODE_OK;
> + }

s/udpate
 /update

Also, more fundamentally, during microcode early testing, isn't it possible for 
internal iterations of the microcode to have the same revision, but be 
different?

This patch would prevent re-loading it - for a seemingly minimal benefit.

Thanks,

Ingo

Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads

[Ingo Molnar]

* Ashok Raj  wrote:

> After updating microcode on one of the threads in the core, the
> thread sibling automatically gets the update since the microcode
> resources are shared. Check the ucode revision on the cpu before
> performing a ucode update.

s/cpu/CPU

> 
> Signed-off-by: Ashok Raj 
> Cc: X86 ML 
> Cc: LKML 
> ---
>  arch/x86/kernel/cpu/microcode/intel.c | 16 +---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c 
> b/arch/x86/kernel/cpu/microcode/intel.c
> index 09b95a7..036d1db 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -776,7 +776,7 @@ static enum ucode_state apply_microcode_intel(int cpu)
>  {
>   struct microcode_intel *mc;
>   struct ucode_cpu_info *uci;
> - struct cpuinfo_x86 *c;
> + struct cpuinfo_x86 *c = _data(cpu);
>   static int prev_rev;
>   u32 rev;
>  
> @@ -793,6 +793,18 @@ static enum ucode_state apply_microcode_intel(int cpu)
>   return UCODE_NFOUND;
>   }
>  
> + rev = intel_get_microcode_revision();
> + /*
> +  * Its possible the microcode got udpated
> +  * because its sibling update was done earlier.
> +  * Skip the udpate in that case.
> +  */
> + if (rev >= mc->hdr.rev) {
> + uci->cpu_sig.rev = rev;
> + c->microcode = rev;
> + return UCODE_OK;
> + }

s/udpate
 /update

Also, more fundamentally, during microcode early testing, isn't it possible for 
internal iterations of the microcode to have the same revision, but be 
different?

This patch would prevent re-loading it - for a seemingly minimal benefit.

Thanks,

Ingo