Date:	Tue, 23 Feb 2016 16:50:37 -0600
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Borislav Petkov <bp@...en8.de>
CC:	<tony.luck@...el.com>, <hpa@...or.com>, <mingo@...hat.com>,
	<tglx@...utronix.de>, <dougthompson@...ssion.com>,
	<mchehab@....samsung.com>, <x86@...nel.org>,
	<linux-edac@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<ashok.raj@...el.com>, <gong.chen@...ux.intel.com>,
	<len.brown@...el.com>, <peterz@...radead.org>,
	<ak@...ux.intel.com>, <alexander.shishkin@...ux.intel.com>
Subject: Re: [PATCH 1/4] EDAC, MCE, AMD: Enable error decoding of Scalable MCA
 errors



On 2/23/16 6:37 AM, Borislav Petkov wrote:
> On Tue, Feb 16, 2016 at 03:45:08PM -0600, Aravind Gopalakrishnan wrote:
>>   /* AMD-specific bits */
>>   #define MCI_STATUS_DEFERRED	(1ULL<<44)  /* declare an uncorrected error */
>>   #define MCI_STATUS_POISON	(1ULL<<43)  /* access poisonous data */
>> +#define MCI_STATUS_TCC		(1ULL<<55)  /* Task context corrupt */
> \n
>

Ack.

>> +/*
>> + * McaX field if set indicates a given bank supports MCA extensions:
>> + *  - Deferred error interrupt type is specifiable by bank
>> + *  - BlkPtr field indicates prescence of extended MISC registers.
> 				^^^^^^^^^
>
> Btw, that's MCi_MISC[BlkPtr] ?

MCi_MISC0[BlkPtr] specifically. Will update the comments about this.

> Also, please integrate a spell checker into your patch creation
> workflow.

Sorry about that. Looks like this pair is not defined in spelling.txt. 
So, might be worth adding there as well?

>> + *    But should not be used to determine MSR numbers
>> + *  - TCC bit is present in MCx_STATUS
> All sentences end with a "."

Will fix.

>
>> +/*
>> + * Enumerating new IP types and HWID values
> Please stop using gerund, i.e., -ing, in comments and commit messages.
>
> "Enumerate new IP ..." is just fine.

Ack.

>
>> + * in ScalableMCA enabled AMD processors
>> + */
>> +#ifdef CONFIG_X86_MCE_AMD
>> +enum ip_types {
> AMD-specific so "amd_ip_types"

Ok, will fix.

>
>> +	F17H_CORE = 0,	/* Core errors */
>> +	DF,		/* Data Fabric */
>> +	UMC,		/* Unified Memory Controller */
>> +	FUSE,		/* FUSE subsystem */
> What's FUSE subsystem?

It's the block for programming FUSE registers.

>
> In any case, this could use a different name in order not to confuse
> with Linux's filesystem in userspace.

Ok, will ask internally as well as to what name suits here.

>> +
>> +struct hwid {
> amd_hwid and so on. All below should have the "amd_" prefix so that it
> is obvious.

Will fix.

>
>> +	const char *ipname;
>> +	unsigned int hwid_value;
>> +};
>> +
>> +extern struct hwid hwid_mappings[N_IP_TYPES];
>> +
>> +enum core_mcatypes {
>> +	LS = 0,		/* Load Store */
>> +	IF,		/* Instruction Fetch */
>> +	L2_CACHE,	/* L2 cache */
>> +	DE,		/* Decoder unit */
>> +	RES,		/* Reserved */
>> +	EX,		/* Execution unit */
>> +	FP,		/* Floating Point */
>> +	L3_CACHE	/* L3 cache */
>> +};
>> +
>> +enum df_mcatypes {
>> +	CS = 0,		/* Coherent Slave */
>> +	PIE		/* Power management, Interrupts, etc */
>> +};
>> +#endif
> So all those are defined here but we have a header for exactly that
> drivers/edac/mce_amd.h. And then you define and export hwid_mappings in
> arch/x86/kernel/cpu/mcheck/mce_amd.c to not use it there.
>
> Why isn't all this in drivers/edac/mce_amd.[ch] ?
>
> And if it is there, then you obviously don't need the "amd_" prefix.

I have a patch that uses these enums here. But I didn't send it out 
along with this patchset as I was testing the patch.
So yes, I need it here and in the EDAC driver.

>
>> +
>>   #endif /* _ASM_X86_MCE_H */
>> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
>> index 5523465..93bccbc 100644
>> --- a/arch/x86/include/asm/msr-index.h
>> +++ b/arch/x86/include/asm/msr-index.h
>> @@ -266,7 +266,9 @@
>>   
>>   /* 'SMCA': AMD64 Scalable MCA */
>>   #define MSR_AMD64_SMCA_MC0_CONFIG	0xc0002004
>> +#define MSR_AMD64_SMCA_MC0_IPID		0xc0002005
>>   #define MSR_AMD64_SMCA_MCx_CONFIG(x)	(MSR_AMD64_SMCA_MC0_CONFIG + 0x10*(x))
>> +#define MSR_AMD64_SMCA_MCx_IPID(x)	(MSR_AMD64_SMCA_MC0_IPID + 0x10*(x))
> Are those MSRs used in multiple files? If not, -> mce.h.

Yes, I'll need them in arch/x86/.../mce_amd.c as well.
A later patch will be using it there.

>>   
>>   
>> +/* Defining HWID to IP type mappings for Scalable MCA */
> " Define ..."

Ack

>
>> +	case L3_CACHE:
>> +		if (xec > (ARRAY_SIZE(f17h_l3_mce_desc) - 1))
>> +			goto wrong_f17hcore_error;
>> +
>> +		pr_cont("%s.\n", f17h_l3_mce_desc[xec]);
>> +		break;
>> +
>> +	default:
>> +		goto wrong_f17hcore_error;
> That's a lot of repeated code. You can assign the desc array to a temp
> variable depending on mca_type and do the if and pr_cont only once using
> that temp variable.

Ok, will simplify.

>
>> +
>> +	case PIE:
>> +		if (xec > (ARRAY_SIZE(f17h_pie_mce_desc) - 1))
>> +			goto wrong_df_error;
>> +
>> +		pr_cont("%s.\n", f17h_pie_mce_desc[xec]);
>> +		break;
> Ditto.
>

Will fix.

>> +
>> +/* Decode errors according to Scalable MCA specification */
>> +static void decode_smca_errors(struct mce *m)
>> +{
>> +	u32 low, high;
>> +	u32 addr = MSR_AMD64_SMCA_MCx_IPID(m->bank);
>> +	unsigned int hwid, mca_type, i;
>> +	u8 xec = XEC(m->status, xec_mask);
>> +
>> +	if (rdmsr_safe(addr, &low, &high)) {
>> +		pr_emerg("Unable to decode errors from banks\n");
> That statement is not very useful in its current form.

How about "Unable to gather IP block that threw the error. Therefore 
cannot decode errors further.\n"

Or should I just remove the pr_emerg()?

>
>> +	for (i = 0; i < ARRAY_SIZE(hwid_mappings); i++)
> So you use those hwid_mappings here. Why aren't they defined here too?

Same reason as the enums-
In a subsequent patch, I'll need it in arch/x86/../mce_amd.c
(I should have probably indicated this in the cover letter so you were 
aware of it. Sorry about that)

>
>> +	case SMU:
>> +		pr_emerg(HW_ERR "SMU Error: ");
>> +		if (xec > (ARRAY_SIZE(f17h_smu_mce_desc) - 1)) {
>> +			pr_cont("Unrecognized error code from SMU MCA bank\n");
>> +			return;
>> +		}
>> +		pr_cont("%s.\n", f17h_smu_mce_desc[xec]);
>> +		break;
> Also a lot of repeated code which could be simplified.

Hmm, will try to simplify it in V2.

>
>>   
>> +	if (mce_flags.smca) {
> ERROR: "mce_flags" [drivers/edac/edac_mce_amd.ko] undefined!
> make[1]: *** [__modpost] Error 1
> make: *** [modules] Error 2
> make: *** Waiting for unfinished jobs....
>
> Just read CPUID again here instead of exporting mce_flags.

Right. Will fix this.

>
>> +		u32 smca_low, smca_high;
>> +		u32 smca_addr = MSR_AMD64_SMCA_MCx_CONFIG(m->bank);
> s/smca_//

Will fix.

>
> Also, all those MSRs should be defined in drivers/edac/mce_amd.h if not
> used outside.

It will be used in arch/x86/../mce_amd.c

>
>> +
>> +		if (!rdmsr_safe(smca_addr, &smca_low, &smca_high) &&
>> +		    (smca_low & MCI_CONFIG_MCAX))
>> +			pr_cont("|%s",
> No need for that break here.

Ok, Will fix.

>
>>   
>> +	case 0x17:
>> +		xec_mask = 0x3f;
>> +		if (!mce_flags.smca) {
>> +			printk(KERN_WARNING "Decoding supported only on Scalable MCA enabled processors\n");
> What is that supposed to do? I thought all new ones will have SMCA...
>
>
If for some reason the CPUID bit is not set, then we should not assume 
the processor supports the features right?

Thanks,
-Aravind.

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