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From: "Jan Beulich" <JBeulich@suse.com>
To: xen-devel <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: [PATCH 5/5] mwait-idle: correct/improve BXT support
Date: Wed, 08 Jun 2016 07:51:38 -0600	[thread overview]
Message-ID: <57583F0A02000078000F320D@prv-mh.provo.novell.com> (raw)
In-Reply-To: <57583E0D02000078000F31F2@prv-mh.provo.novell.com>

[-- Attachment #1: Type: text/plain, Size: 2084 bytes --]

Linux commit 5dcef69486 ("intel_idle: add BXT support") added an
8-element lookup array with just a 2-bit value used for lookups. As per
the SDM that bit field is really 3 bits wide. Since the top two array
entries are zero, deal with the resulting invalid (zero) values by
moving the zero-MSR-value check into irtl_2_usec() and having that
function's caller check its result instead.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -922,7 +922,10 @@ static unsigned long long __init irtl_2_
 {
 	unsigned long long ns;
 
-	ns = irtl_ns_units[(irtl >> 10) & 0x3];
+	if (!irtl)
+		return 0;
+
+	ns = irtl_ns_units[(irtl >> 10) & 0x7];
 
 	return (irtl & 0x3FF) * ns / 1000;
 }
@@ -935,43 +938,39 @@ static unsigned long long __init irtl_2_
 static void __init bxt_idle_state_table_update(void)
 {
 	unsigned long long msr;
+	unsigned int usec;
 
 	rdmsrl(MSR_PKGC6_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[2].exit_latency = usec;
 		bxt_cstates[2].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC7_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[3].exit_latency = usec;
 		bxt_cstates[3].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC8_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[4].exit_latency = usec;
 		bxt_cstates[4].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC9_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[5].exit_latency = usec;
 		bxt_cstates[5].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC10_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[6].exit_latency = usec;
 		bxt_cstates[6].target_residency = usec;
 	}




[-- Attachment #2: x86-mwait-idle-BXT-time-unit.patch --]
[-- Type: text/plain, Size: 2121 bytes --]

mwait-idle: correct/improve BXT support

Linux commit 5dcef69486 ("intel_idle: add BXT support") added an
8-element lookup array with just a 2-bit value used for lookups. As per
the SDM that bit field is really 3 bits wide. Since the top two array
entries are zero, deal with the resulting invalid (zero) values by
moving the zero-MSR-value check into irtl_2_usec() and having that
function's caller check its result instead.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -922,7 +922,10 @@ static unsigned long long __init irtl_2_
 {
 	unsigned long long ns;
 
-	ns = irtl_ns_units[(irtl >> 10) & 0x3];
+	if (!irtl)
+		return 0;
+
+	ns = irtl_ns_units[(irtl >> 10) & 0x7];
 
 	return (irtl & 0x3FF) * ns / 1000;
 }
@@ -935,43 +938,39 @@ static unsigned long long __init irtl_2_
 static void __init bxt_idle_state_table_update(void)
 {
 	unsigned long long msr;
+	unsigned int usec;
 
 	rdmsrl(MSR_PKGC6_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[2].exit_latency = usec;
 		bxt_cstates[2].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC7_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[3].exit_latency = usec;
 		bxt_cstates[3].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC8_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[4].exit_latency = usec;
 		bxt_cstates[4].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC9_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[5].exit_latency = usec;
 		bxt_cstates[5].target_residency = usec;
 	}
 
 	rdmsrl(MSR_PKGC10_IRTL, msr);
-	if (msr) {
-		unsigned int usec = irtl_2_usec(msr);
-
+	usec = irtl_2_usec(msr);
+	if (usec) {
 		bxt_cstates[6].exit_latency = usec;
 		bxt_cstates[6].target_residency = usec;
 	}

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  parent reply	other threads:[~2016-06-08 13:51 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-08 13:47 [PATCH 0/5] x86: mwait-idle updates Jan Beulich
2016-06-08 13:49 ` [PATCH 1/5] mwait-idle: add SKX support Jan Beulich
2016-06-08 13:50 ` [PATCH 2/5] mwait-idle: add KBL support Jan Beulich
2016-06-08 13:50 ` [PATCH 3/5] mwait-idle: add BXT support Jan Beulich
2016-06-08 13:51 ` [PATCH 4/5] mwait-idle: add a missing __init annotation Jan Beulich
2016-06-08 13:51 ` Jan Beulich [this message]
2016-06-09 13:20 ` [PATCH 0/5] x86: mwait-idle updates Andrew Cooper
2016-06-09 13:33   ` Jan Beulich

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