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From: Andy Lutomirski <luto@kernel.org>
To: X86 ML <x86@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	KVM list <kvm@vger.kernel.org>,
	Arjan van de Ven <arjan@linux.intel.com>,
	xen-devel <Xen-devel@lists.xen.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>
Subject: [PATCH v4 5/5] x86/msr: Set the return value to zero when native_rdmsr_safe fails
Date: Sat, 12 Mar 2016 10:08:52 -0800	[thread overview]
Message-ID: <85c0bf533f7845697ee3c0f8833fc249fd221f31.1457805972.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1457805972.git.luto@kernel.org>
In-Reply-To: <cover.1457805972.git.luto@kernel.org>

This will cause unchecked native_rdmsr_safe failures to return
deterministic results.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/msr.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 13da359881d7..e97e79f8a22b 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -109,7 +109,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
 	asm volatile("2: rdmsr ; xor %[err],%[err]\n"
 		     "1:\n\t"
 		     ".section .fixup,\"ax\"\n\t"
-		     "3:  mov %[fault],%[err] ; jmp 1b\n\t"
+		     "3: mov %[fault],%[err]\n\t"
+		     "xorl %%eax, %%eax\n\t"
+		     "xorl %%edx, %%edx\n\t"
+		     "jmp 1b\n\t"
 		     ".previous\n\t"
 		     _ASM_EXTABLE(2b, 3b)
 		     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
-- 
2.5.0

WARNING: multiple messages have this Message-ID (diff)
From: Andy Lutomirski <luto@kernel.org>
To: X86 ML <x86@kernel.org>
Cc: KVM list <kvm@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	xen-devel <Xen-devel@lists.xen.org>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH v4 5/5] x86/msr: Set the return value to zero when native_rdmsr_safe fails
Date: Sat, 12 Mar 2016 10:08:52 -0800	[thread overview]
Message-ID: <85c0bf533f7845697ee3c0f8833fc249fd221f31.1457805972.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1457805972.git.luto@kernel.org>
In-Reply-To: <cover.1457805972.git.luto@kernel.org>

This will cause unchecked native_rdmsr_safe failures to return
deterministic results.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/msr.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 13da359881d7..e97e79f8a22b 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -109,7 +109,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
 	asm volatile("2: rdmsr ; xor %[err],%[err]\n"
 		     "1:\n\t"
 		     ".section .fixup,\"ax\"\n\t"
-		     "3:  mov %[fault],%[err] ; jmp 1b\n\t"
+		     "3: mov %[fault],%[err]\n\t"
+		     "xorl %%eax, %%eax\n\t"
+		     "xorl %%edx, %%edx\n\t"
+		     "jmp 1b\n\t"
 		     ".previous\n\t"
 		     _ASM_EXTABLE(2b, 3b)
 		     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
-- 
2.5.0


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  parent reply	other threads:[~2016-03-12 18:09 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-12 18:08 [PATCH v4 0/5] [PATCH v3 0/5] Improve non-"safe" MSR access failure handling Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 1/5] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski
2016-03-14 11:57   ` Borislav Petkov
2016-03-14 17:07     ` Andy Lutomirski
2016-03-14 17:07     ` Andy Lutomirski
2016-03-14 11:57   ` Borislav Petkov
2016-03-12 18:08 ` Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops Andy Lutomirski
2016-03-14 12:02   ` Borislav Petkov
2016-03-14 12:02   ` Borislav Petkov
2016-03-14 17:05     ` Andy Lutomirski
2016-03-14 17:11       ` Linus Torvalds
2016-03-14 17:17         ` Andy Lutomirski
2016-03-14 18:04           ` Linus Torvalds
2016-03-14 18:10             ` Andy Lutomirski
2016-03-14 18:15               ` Linus Torvalds
2016-03-14 18:15               ` Linus Torvalds
2016-03-14 18:24                 ` Andy Lutomirski
2016-03-14 18:24                 ` Andy Lutomirski
2016-03-14 18:40                   ` Linus Torvalds
2016-03-14 18:48                     ` Andy Lutomirski
2016-03-15 10:22                       ` Ingo Molnar
2016-03-15 10:26                         ` Ingo Molnar
2016-03-15 10:26                         ` Ingo Molnar
2016-03-15 10:22                       ` Ingo Molnar
2016-03-14 18:48                     ` Andy Lutomirski
2016-03-14 18:40                   ` Linus Torvalds
2016-03-14 20:18               ` Peter Zijlstra
2016-03-14 20:18               ` Peter Zijlstra
2016-03-14 18:10             ` Andy Lutomirski
2016-03-14 18:10             ` Linus Torvalds
2016-03-14 18:10             ` Linus Torvalds
2016-03-15 10:21             ` Ingo Molnar
2016-03-15 10:21             ` Ingo Molnar
2016-03-14 18:04           ` Linus Torvalds
2016-03-14 17:17         ` Andy Lutomirski
2016-03-14 17:05     ` Andy Lutomirski
2016-03-12 18:08 ` Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 3/5] x86/paravirt: Add paravirt_{read,write}_msr Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 3/5] x86/paravirt: Add paravirt_{read, write}_msr Andy Lutomirski
2016-03-12 18:08 ` [PATCH v4 4/5] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y Andy Lutomirski
2016-03-12 18:08 ` Andy Lutomirski
2016-03-12 18:08 ` Andy Lutomirski [this message]
2016-03-12 18:08   ` [PATCH v4 5/5] x86/msr: Set the return value to zero when native_rdmsr_safe fails Andy Lutomirski
2016-03-14 14:32 ` [Xen-devel] [PATCH v4 0/5] [PATCH v3 0/5] Improve non-"safe" MSR access failure handling Boris Ostrovsky
2016-03-14 14:32 ` Boris Ostrovsky

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