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Commit 13e457e0 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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KVM: x86: Emulator does not decode clflush well 



Currently, all group15 instructions are decoded as clflush (e.g., mfence,
xsave).  In addition, the clflush instruction requires no prefix (66/f2/f3)
would exist. If prefix exists it may encode a different instruction (e.g.,
clflushopt).

Creating a group for clflush, and different group for each prefix.

This has been the case forever, but the next patch needs the cflush group
in order to fix a bug introduced in 3.17.

Fixes: 41061cdb
Cc: stable@vger.kernel.org
Signed-off-by: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a430c916

arch/x86/kvm/emulate.c

+17 −3
Original line number Diff line number Diff line
@@ -3462,6 +3462,12 @@ static int em_bswap(struct x86_emulate_ctxt *ctxt) 
	return X86EMUL_CONTINUE;

}



static int em_clflush(struct x86_emulate_ctxt *ctxt)

{

	/* emulating clflush regardless of cpuid */

	return X86EMUL_CONTINUE;

}



static bool valid_cr(int nr)

{

	switch (nr) {
@@ -3800,6 +3806,16 @@ static const struct opcode group11[] = { 
	X7(D(Undefined)),

};



static const struct gprefix pfx_0f_ae_7 = {

	I(0, em_clflush), N, N, N,

};



static const struct group_dual group15 = { {

	N, N, N, N, N, N, N, GP(0, &pfx_0f_ae_7),

}, {

	N, N, N, N, N, N, N, N,

} };



static const struct gprefix pfx_0f_6f_0f_7f = {

	I(Mmx, em_mov), I(Sse | Aligned, em_mov), N, I(Sse | Unaligned, em_mov),

};
@@ -4063,7 +4079,7 @@ static const struct opcode twobyte_table[256] = { 
	F(DstMem | SrcReg | ModRM | BitOp | Lock | PageTable, em_bts),

	F(DstMem | SrcReg | Src2ImmByte | ModRM, em_shrd),

	F(DstMem | SrcReg | Src2CL | ModRM, em_shrd),

	D(ModRM), F(DstReg | SrcMem | ModRM, em_imul),

	GD(0, &group15), F(DstReg | SrcMem | ModRM, em_imul),

	/* 0xB0 - 0xB7 */

	I2bv(DstMem | SrcReg | ModRM | Lock | PageTable, em_cmpxchg),

	I(DstReg | SrcMemFAddr | ModRM | Src2SS, em_lseg),
@@ -4993,8 +5009,6 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) 
	case 0x90 ... 0x9f:     /* setcc r/m8 */

		ctxt->dst.val = test_cc(ctxt->b, ctxt->eflags);

		break;

	case 0xae:              /* clflush */

		break;

	case 0xb6 ... 0xb7:	/* movzx */

		ctxt->dst.bytes = ctxt->op_bytes;

		ctxt->dst.val = (ctxt->src.bytes == 1) ? (u8) ctxt->src.val