Patch "KVM: x86: add asm_safe wrapper" has been added to the 4.9-stable tree

Patch "KVM: x86: add asm_safe wrapper" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    KVM: x86: add asm_safe wrapper

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-x86-add-asm_safe-wrapper.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From aabba3c6abd50b05b1fc2c6ec44244aa6bcda576 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>
Date: Tue, 8 Nov 2016 20:54:18 +0100
Subject: KVM: x86: add asm_safe wrapper
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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From: Radim Krčmář <rkrcmar@redhat.com>

commit aabba3c6abd50b05b1fc2c6ec44244aa6bcda576 upstream.

Move the existing exception handling for inline assembly into a macro
and switch its return values to X86EMUL type.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/emulate.c |   34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -447,6 +447,26 @@ FOP_END;
 FOP_START(salc) "pushf; sbb %al, %al; popf \n\t" FOP_RET
 FOP_END;
 
+/*
+ * XXX: inoutclob user must know where the argument is being expanded.
+ *      Relying on CC_HAVE_ASM_GOTO would allow us to remove _fault.
+ */
+#define asm_safe(insn, inoutclob...) \
+({ \
+	int _fault = 0; \
+ \
+	asm volatile("1:" insn "\n" \
+	             "2:\n" \
+	             ".pushsection .fixup, \"ax\"\n" \
+	             "3: movl $1, %[_fault]\n" \
+	             "   jmp  2b\n" \
+	             ".popsection\n" \
+	             _ASM_EXTABLE(1b, 3b) \
+	             : [_fault] "+qm"(_fault) inoutclob ); \
+ \
+	_fault ? X86EMUL_UNHANDLEABLE : X86EMUL_CONTINUE; \
+})
+
 static int emulator_check_intercept(struct x86_emulate_ctxt *ctxt,
 				    enum x86_intercept intercept,
 				    enum x86_intercept_stage stage)
@@ -5098,21 +5118,13 @@ static bool string_insn_completed(struct
 
 static int flush_pending_x87_faults(struct x86_emulate_ctxt *ctxt)
 {
-	bool fault = false;
+	int rc;
 
 	ctxt->ops->get_fpu(ctxt);
-	asm volatile("1: fwait \n\t"
-		     "2: \n\t"
-		     ".pushsection .fixup,\"ax\" \n\t"
-		     "3: \n\t"
-		     "movb $1, %[fault] \n\t"
-		     "jmp 2b \n\t"
-		     ".popsection \n\t"
-		     _ASM_EXTABLE(1b, 3b)
-		     : [fault]"+qm"(fault));
+	rc = asm_safe("fwait");
 	ctxt->ops->put_fpu(ctxt);
 
-	if (unlikely(fault))
+	if (unlikely(rc != X86EMUL_CONTINUE))
 		return emulate_exception(ctxt, MF_VECTOR, 0, false);
 
 	return X86EMUL_CONTINUE;


Patches currently in stable-queue which might be from rkrcmar@redhat.com are

queue-4.9/kvm-x86-add-asm_safe-wrapper.patch
queue-4.9/kvm-eventfd-fix-null-deref-irqbypass-consumer.patch
queue-4.9/kvm-x86-add-align16-instruction-flag.patch
queue-4.9/kvm-x86-fix-null-deref-in-vcpu_scan_ioapic.patch
queue-4.9/kvm-x86-emulate-fxsave-and-fxrstor.patch