ACK: [SRU Artful] x86/mce/AMD: Allow any CPU to initialize the smca_banks array

[Colin Ian King]

On 17/11/17 11:40, Timo Aaltonen wrote:
> From: Yazen Ghannam <yazen.ghannam at amd.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1732894
> 
> Current SMCA implementations have the same banks on each CPU with the
> non-core banks only visible to a "master thread" on each die. Practically,
> this means the smca_banks array, which describes the banks, only needs to
> be populated once by a single master thread.
> 
> CPU 0 seemed like a good candidate to do the populating. However, it's
> possible that CPU 0 is not enabled in which case the smca_banks array won't
> be populated.
> 
> Rather than try to figure out another master thread to do the populating,
> we should just allow any CPU to populate the array.
> 
> Drop the CPU 0 check and return early if the bank was already initialized.
> Also, drop the WARNing about an already initialized bank, since this will
> be a common, expected occurrence.
> 
> The smca_banks array is only populated at boot time and CPUs are brought
> online sequentially. So there's no need for locking around the array.
> 
> If the first CPU up is a master thread, then it will populate the array
> with all banks, core and non-core. Every CPU afterwards will return
> early. If the first CPU up is not a master thread, then it will populate
> the array with all core banks. The first CPU afterwards that is a master
> thread will skip populating the core banks and continue populating the
> non-core banks.
> 
> Signed-off-by: Yazen Ghannam <yazen.ghannam at amd.com>
> Signed-off-by: Borislav Petkov <bp at suse.de>
> Acked-by: Jack Miller <jack at codezen.org>
> Cc: Linus Torvalds <torvalds at linux-foundation.org>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Tony Luck <tony.luck at intel.com>
> Cc: linux-edac <linux-edac at vger.kernel.org>
> Link: http://lkml.kernel.org/r/20170724101228.17326-4-bp@alien8.de
> Signed-off-by: Ingo Molnar <mingo at kernel.org>
> (cherry picked from commit 9662d43f523dfc0dc242ec29c2921c43898d6ae5)
> Signed-off-by: Timo Aaltonen <tjaalton at debian.org>
> ---
>  arch/x86/kernel/cpu/mcheck/mce_amd.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index 9e314bcf67cc..5ce1a5689162 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -201,8 +201,8 @@ static void smca_configure(unsigned int bank, unsigned int cpu)
>  		wrmsr(smca_config, low, high);
>  	}
>  
> -	/* Collect bank_info using CPU 0 for now. */
> -	if (cpu)
> +	/* Return early if this bank was already initialized. */
> +	if (smca_banks[bank].hwid)
>  		return;
>  
>  	if (rdmsr_safe_on_cpu(cpu, MSR_AMD64_SMCA_MCx_IPID(bank), &low, &high)) {
> @@ -216,11 +216,6 @@ static void smca_configure(unsigned int bank, unsigned int cpu)
>  	for (i = 0; i < ARRAY_SIZE(smca_hwid_mcatypes); i++) {
>  		s_hwid = &smca_hwid_mcatypes[i];
>  		if (hwid_mcatype == s_hwid->hwid_mcatype) {
> -
> -			WARN(smca_banks[bank].hwid,
> -			     "Bank %s already initialized!\n",
> -			     smca_get_name(s_hwid->bank_type));
> -
>  			smca_banks[bank].hwid = s_hwid;
>  			smca_banks[bank].id = low;
>  			smca_banks[bank].sysfs_id = s_hwid->count++;
> 

Clean upstream cherry pick.

Acked-by: Colin Ian King <colin.king at canonical.com>