linux-kernel - Re: [PATCH V2 3/6] x86/mce: Define 'SUCCOR' cpuid bit

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Date:	Wed, 6 May 2015 20:49:17 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	tony.luck@...el.com, jiang.liu@...ux.intel.com, yinghai@...nel.org,
	x86@...nel.org, dvlasenk@...hat.com, JBeulich@...e.com,
	slaoub@...il.com, luto@...capital.net, dave.hansen@...ux.intel.com,
	oleg@...hat.com, rostedt@...dmis.org, rusty@...tcorp.com.au,
	prarit@...hat.com, linux@...musvillemoes.dk, jroedel@...e.de,
	andriy.shevchenko@...ux.intel.com, macro@...ux-mips.org,
	wangnan0@...wei.com, linux-kernel@...r.kernel.org,
	linux-edac@...r.kernel.org, rric@...nel.org
Subject: Re: [PATCH V2 3/6] x86/mce: Define 'SUCCOR' cpuid bit

On Wed, May 06, 2015 at 06:58:55AM -0500, Aravind Gopalakrishnan wrote:
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index e535533..6d218ac 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -1639,7 +1639,8 @@ static void __mcheck_cpu_init_vendor(struct cpuinfo_x86 *c)
>  		break;
>  	case X86_VENDOR_AMD:
>  		mce_amd_feature_init(c);
> -		mce_flags.overflow_recov = cpuid_ebx(0x80000007) & 0x1;
> +		mce_flags.overflow_recov = !!(cpuid_ebx(0x80000007) & BIT(0));
> +		mce_flags.succor	 = !!(cpuid_ebx(0x80000007) & BIT(1));

Yuck, I thought gcc would be smart enough to recognize that we're
calling CPUID twice with the same params and save us the work but nooo.
asm looks yucky.

Oh well, I had to save us the second CPUID read and beef up the commit
message:

---
From: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Date: Wed, 6 May 2015 06:58:55 -0500
Subject: [PATCH] x86/mce: Add support for deferred errors on AMD

Deferred errors indicate error conditions that were not corrected, but
those errors have not been consumed yet. They require no action from
S/W (or action is optional). These errors provide info about a latent
uncorrectable MCE that can occur when a poisoned data is consumed by the
processor.

Newer AMD processors can generate deferred errors and can be configured
to generate APIC interrupts on such events.

SUCCOR stands for S/W UnCorrectable error COntainment and Recovery.
It indicates support for data poisoning in HW and deferred error
interrupts.

Add new bitfield to mce_vendor_flags for this. We use this to verify
presence of deferred error interrupts before we enable them in mce_amd.c

While at it, clarify comments in mce_vendor_flags to provide an
indication of usages of the bitfields.

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: x86-ml <x86@...nel.org>
Cc: linux-edac <linux-edac@...r.kernel.org>
Link: http://lkml.kernel.org/r/1430913538-1415-4-git-send-email-Aravind.Gopalakrishnan@amd.com
[ beef up commit message, do CPUID(8000_0007) only once. ]
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/include/asm/mce.h       | 15 +++++++++++++--
 arch/x86/kernel/cpu/mcheck/mce.c | 10 ++++++++--
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 1f5a86d518db..407ced642ac1 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -117,8 +117,19 @@ struct mca_config {
 };
 
 struct mce_vendor_flags {
-	__u64		overflow_recov	: 1, /* cpuid_ebx(80000007) */
-			__reserved_0	: 63;
+			/*
+			 * overflow recovery cpuid bit indicates that overflow
+			 * conditions are not fatal
+			 */
+	__u64		overflow_recov	: 1,
+
+			/*
+			 * SUCCOR stands for S/W UnCorrectable error COntainment
+			 * and Recovery. It indicates support for data poisoning
+			 * in HW and deferred error interrupts.
+			 */
+			succor		: 1,
+			__reserved_0	: 62;
 };
 extern struct mce_vendor_flags mce_flags;
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index e535533d5ab8..521e5016aca6 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1637,10 +1637,16 @@ static void __mcheck_cpu_init_vendor(struct cpuinfo_x86 *c)
 		mce_intel_feature_init(c);
 		mce_adjust_timer = cmci_intel_adjust_timer;
 		break;
-	case X86_VENDOR_AMD:
+
+	case X86_VENDOR_AMD: {
+		u32 ebx = cpuid_ebx(0x80000007);
+
 		mce_amd_feature_init(c);
-		mce_flags.overflow_recov = cpuid_ebx(0x80000007) & 0x1;
+		mce_flags.overflow_recov = !!(ebx & BIT(0));
+		mce_flags.succor	 = !!(ebx & BIT(1));
 		break;
+		}
+
 	default:
 		break;
 	}
-- 
2.3.5

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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