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Commit d40a6898 authored by Paolo Bonzini's avatar Paolo Bonzini
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KVM: emulate: protect checks on ctxt->d by a common "if (unlikely())" 



There are several checks for "peculiar" aspects of instructions in both
x86_decode_insn and x86_emulate_insn.  Group them together, and guard
them with a single "if" that lets the processor quickly skip them all.
Make this more effective by adding two more flag bits that say whether the
.intercept and .check_perm fields are valid.  We will reuse these
flags later to avoid initializing fields of the emulate_ctxt struct.

This skims about 30 cycles for each emulated instructions, which is
approximately a 3% improvement.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e24186e0

arch/x86/kvm/emulate.c

+94 −81
Original line number Diff line number Diff line
@@ -162,6 +162,8 @@ 
#define NoWrite     ((u64)1 << 45)  /* No writeback */

#define SrcWrite    ((u64)1 << 46)  /* Write back src operand */

#define NoMod	    ((u64)1 << 47)  /* Mod field is ignored */

#define Intercept   ((u64)1 << 48)  /* Has valid intercept field */

#define CheckPerm   ((u64)1 << 49)  /* Has valid check_perm field */



#define DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
@@ -3546,9 +3548,9 @@ static int check_perm_out(struct x86_emulate_ctxt *ctxt) 
}



#define D(_y) { .flags = (_y) }

#define DI(_y, _i) { .flags = (_y), .intercept = x86_intercept_##_i }

#define DIP(_y, _i, _p) { .flags = (_y), .intercept = x86_intercept_##_i, \

		      .check_perm = (_p) }

#define DI(_y, _i) { .flags = (_y)|Intercept, .intercept = x86_intercept_##_i }

#define DIP(_y, _i, _p) { .flags = (_y)|Intercept|CheckPerm, \

		      .intercept = x86_intercept_##_i, .check_perm = (_p) }

#define N    D(NotImpl)

#define EXT(_f, _e) { .flags = ((_f) | RMExt), .u.group = (_e) }

#define G(_f, _g) { .flags = ((_f) | Group | ModRM), .u.group = (_g) }
@@ -3557,10 +3559,10 @@ static int check_perm_out(struct x86_emulate_ctxt *ctxt) 
#define I(_f, _e) { .flags = (_f), .u.execute = (_e) }

#define F(_f, _e) { .flags = (_f) | Fastop, .u.fastop = (_e) }

#define II(_f, _e, _i) \

	{ .flags = (_f), .u.execute = (_e), .intercept = x86_intercept_##_i }

	{ .flags = (_f)|Intercept, .u.execute = (_e), .intercept = x86_intercept_##_i }

#define IIP(_f, _e, _i, _p) \

	{ .flags = (_f), .u.execute = (_e), .intercept = x86_intercept_##_i, \

	  .check_perm = (_p) }

	{ .flags = (_f)|Intercept|CheckPerm, .u.execute = (_e), \

	  .intercept = x86_intercept_##_i, .check_perm = (_p) }

#define GP(_f, _g) { .flags = ((_f) | Prefix), .u.gprefix = (_g) }



#define D2bv(_f)      D((_f) | ByteOp), D(_f)
@@ -4393,6 +4395,13 @@ done_prefixes: 
		return EMULATION_FAILED;



	ctxt->execute = opcode.u.execute;



	if (unlikely(ctxt->d &

		     (NotImpl|EmulateOnUD|Stack|Op3264|Sse|Mmx|Intercept|CheckPerm))) {

		/*

		 * These are copied unconditionally here, and checked unconditionally

		 * in x86_emulate_insn.

		 */

		ctxt->check_perm = opcode.check_perm;

		ctxt->intercept = opcode.intercept;
@@ -4416,6 +4425,7 @@ done_prefixes: 
			ctxt->op_bytes = 16;

		else if (ctxt->d & Mmx)

			ctxt->op_bytes = 8;

	}



	/* ModRM and SIB bytes. */

	if (ctxt->d & ModRM) {
@@ -4549,6 +4559,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) 
		goto done;

	}



	if (unlikely(ctxt->d &

		     (No64|Undefined|Sse|Mmx|Intercept|CheckPerm|Priv|Prot|String))) {

		if ((ctxt->mode == X86EMUL_MODE_PROT64 && (ctxt->d & No64)) ||

				(ctxt->d & Undefined)) {

			rc = emulate_ud(ctxt);
@@ -4620,6 +4632,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) 
				goto done;

			}

		}

	}



	if ((ctxt->src.type == OP_MEM) && !(ctxt->d & NoAccess)) {

		rc = segmented_read(ctxt, ctxt->src.addr.mem,