linux-kernel - [PATCH v2 1/4] KVM: x86: add Align16 instruction flag

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Date:   Wed,  2 Nov 2016 19:45:34 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Bandan Das <bsd@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>
Subject: [PATCH v2 1/4] KVM: x86: add Align16 instruction flag

Needed for FXSAVE and FXRSTOR.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 v2: split into a separate patch
---
 arch/x86/kvm/emulate.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 4e95d3eb2955..557dbb9e5bec 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -171,6 +171,7 @@
 #define NearBranch  ((u64)1 << 52)  /* Near branches */
 #define No16	    ((u64)1 << 53)  /* No 16 bit operand */
 #define IncSP       ((u64)1 << 54)  /* SP is incremented before ModRM calc */
+#define Aligned16   ((u64)1 << 55)  /* Aligned to 16 byte boundary (e.g. FXSAVE) */
 
 #define DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
 
@@ -632,21 +633,24 @@ static void set_segment_selector(struct x86_emulate_ctxt *ctxt, u16 selector,
  * depending on whether they're AVX encoded or not.
  *
  * Also included is CMPXCHG16B which is not a vector instruction, yet it is
- * subject to the same check.
+ * subject to the same check.  FXSAVE and FXRSTOR are checked here too as their
+ * 512 bytes of data must be aligned to a 16 byte boundary.
  */
-static bool insn_aligned(struct x86_emulate_ctxt *ctxt, unsigned size)
+static unsigned insn_alignment(struct x86_emulate_ctxt *ctxt, unsigned size)
 {
 	if (likely(size < 16))
-		return false;
+		return 1;
 
 	if (ctxt->d & Aligned)
-		return true;
+		return size;
 	else if (ctxt->d & Unaligned)
-		return false;
+		return 1;
 	else if (ctxt->d & Avx)
-		return false;
+		return 1;
+	else if (ctxt->d & Aligned16)
+		return 16;
 	else
-		return true;
+		return size;
 }
 
 static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
@@ -704,7 +708,7 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
 		}
 		break;
 	}
-	if (insn_aligned(ctxt, size) && ((la & (size - 1)) != 0))
+	if (la & (insn_alignment(ctxt, size) - 1))
 		return emulate_gp(ctxt, 0);
 	return X86EMUL_CONTINUE;
 bad:
-- 
2.10.1