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From: tip-bot for Borislav Petkov <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: mingo@kernel.org, hpa@zytor.com, tglx@linutronix.de,
	linux-kernel@vger.kernel.org, bp@suse.de
Subject: [tip:x86/mce] x86/MSR: Carve out bare minimum accessors
Date: Mon, 23 Jan 2017 01:07:45 -0800	[thread overview]
Message-ID: <tip-a585df8edabdb47ae25214ebb3a627ca7ce800d3@git.kernel.org> (raw)
In-Reply-To: <20170120202955.4091-3-bp@alien8.de>

Commit-ID:  a585df8edabdb47ae25214ebb3a627ca7ce800d3
Gitweb:     http://git.kernel.org/tip/a585df8edabdb47ae25214ebb3a627ca7ce800d3
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Fri, 20 Jan 2017 21:29:41 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 23 Jan 2017 10:02:45 +0100

x86/MSR: Carve out bare minimum accessors

Add __rdmsr() and __wrmsr() which *only* read and write an MSR with
exception handling. Those are going to be used in early code, like the
microcode loader, which cannot stomach tracing code piggybacking on the
MSR operation.

While at it, get rid of __native_write_msr_notrace().

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170120202955.4091-3-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 arch/x86/include/asm/apic.h |  2 +-
 arch/x86/include/asm/msr.h  | 51 +++++++++++++++++++++++++++------------------
 2 files changed, 32 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 0c5fbc6..eff8e36 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -195,7 +195,7 @@ static inline void native_apic_msr_write(u32 reg, u32 v)
 
 static inline void native_apic_msr_eoi_write(u32 reg, u32 v)
 {
-	wrmsr_notrace(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
+	__wrmsr(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
 }
 
 static inline u32 native_apic_msr_read(u32 reg)
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index db0b90c..898dba2 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -80,7 +80,14 @@ static inline void do_trace_read_msr(unsigned int msr, u64 val, int failed) {}
 static inline void do_trace_rdpmc(unsigned int msr, u64 val, int failed) {}
 #endif
 
-static inline unsigned long long native_read_msr(unsigned int msr)
+/*
+ * __rdmsr() and __wrmsr() are the two primitives which are the bare minimum MSR
+ * accessors and should not have any tracing or other functionality piggybacking
+ * on them - those are *purely* for accessing MSRs and nothing more. So don't even
+ * think of extending them - you will be slapped with a stinking trout or a frozen
+ * shark will reach you, wherever you are! You've been warned.
+ */
+static inline unsigned long long notrace __rdmsr(unsigned int msr)
 {
 	DECLARE_ARGS(val, low, high);
 
@@ -88,11 +95,30 @@ static inline unsigned long long native_read_msr(unsigned int msr)
 		     "2:\n"
 		     _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_rdmsr_unsafe)
 		     : EAX_EDX_RET(val, low, high) : "c" (msr));
-	if (msr_tracepoint_active(__tracepoint_read_msr))
-		do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), 0);
+
 	return EAX_EDX_VAL(val, low, high);
 }
 
+static inline void notrace __wrmsr(unsigned int msr, u32 low, u32 high)
+{
+	asm volatile("1: wrmsr\n"
+		     "2:\n"
+		     _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
+		     : : "c" (msr), "a"(low), "d" (high) : "memory");
+}
+
+static inline unsigned long long native_read_msr(unsigned int msr)
+{
+	unsigned long long val;
+
+	val = __rdmsr(msr);
+
+	if (msr_tracepoint_active(__tracepoint_read_msr))
+		do_trace_read_msr(msr, val, 0);
+
+	return val;
+}
+
 static inline unsigned long long native_read_msr_safe(unsigned int msr,
 						      int *err)
 {
@@ -116,29 +142,14 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
 
 /* Can be uninlined because referenced by paravirt */
 static inline void notrace
-__native_write_msr_notrace(unsigned int msr, u32 low, u32 high)
-{
-	asm volatile("1: wrmsr\n"
-		     "2:\n"
-		     _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
-		     : : "c" (msr), "a"(low), "d" (high) : "memory");
-}
-
-/* Can be uninlined because referenced by paravirt */
-static inline void notrace
 native_write_msr(unsigned int msr, u32 low, u32 high)
 {
-	__native_write_msr_notrace(msr, low, high);
+	__wrmsr(msr, low, high);
+
 	if (msr_tracepoint_active(__tracepoint_write_msr))
 		do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
 }
 
-static inline void
-wrmsr_notrace(unsigned int msr, u32 low, u32 high)
-{
-	__native_write_msr_notrace(msr, low, high);
-}
-
 /* Can be uninlined because referenced by paravirt */
 static inline int notrace
 native_write_msr_safe(unsigned int msr, u32 low, u32 high)

  reply	other threads:[~2017-01-23  9:07 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-20 20:29 [PATCH 00/16 v2] x86/microcode: 4.11 queue Borislav Petkov
2017-01-20 20:29 ` [PATCH 01/16] x86/microcode/intel: Drop stashed AP patch pointer optimization Borislav Petkov
2017-01-23  9:07   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 02/16] x86/MSR: Carve out bare minimum accessors Borislav Petkov
2017-01-23  9:07   ` tip-bot for Borislav Petkov [this message]
2017-01-20 20:29 ` [PATCH 03/16] x86/microcode: Convert to bare minimum MSR accessors Borislav Petkov
2017-01-23  9:08   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 04/16] x86/microcode/AMD: Clean up find_equiv_id() Borislav Petkov
2017-01-23  9:08   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 05/16] x86/microcode/AMD: Shorten function parameter's name Borislav Petkov
2017-01-23  9:09   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 06/16] x86/microcode/AMD: Extend the container struct Borislav Petkov
2017-01-23  9:09   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 07/16] x86/microcode/AMD: Rework container parsing Borislav Petkov
2017-01-23  9:10   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 08/16] x86/microcode: Decrease CPUID use Borislav Petkov
2017-01-23  9:10   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 09/16] x86/microcode/AMD: Get rid of global this_equiv_id Borislav Petkov
2017-01-23  9:11   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 10/16] x86/microcode/AMD: Use find_microcode_in_initrd() Borislav Petkov
2017-01-23  9:11   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 11/16] x86/microcode: Remove local vendor variable Borislav Petkov
2017-01-23  9:12   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 12/16] x86/microcode/AMD: Check patch level only on the BSP Borislav Petkov
2017-01-23  9:12   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 13/16] x86/microcode/AMD: Unify load_ucode_amd_ap() Borislav Petkov
2017-01-23  9:13   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 14/16] x86/microcode/AMD: Simplify saving from initrd Borislav Petkov
2017-01-23  9:13   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 15/16] x86/microcode/AMD: Remove AP scanning optimization Borislav Petkov
2017-01-23  9:14   ` [tip:x86/mce] " tip-bot for Borislav Petkov
2017-01-20 20:29 ` [PATCH 16/16] x86/microcode/AMD: Remove struct cont_desc.eq_id Borislav Petkov
2017-01-23  9:14   ` [tip:x86/mce] " tip-bot for Borislav Petkov

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