Commit 9b88ae99 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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KVM: x86: MOV CR/DR emulation should ignore mod 



MOV CR/DR instructions ignore the mod field (in the ModR/M byte). As the SDM
states: "The 2 bits in the mod field are ignored".  Accordingly, the second
operand of these instructions is always a general purpose register.

The current emulator implementation does not do so. If the mod bits do not
equal 3, it expects the second operand to be in memory.

Signed-off-by: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent fc57ac2c

arch/x86/kvm/emulate.c

+8 −5
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ 
#define Fastop      ((u64)1 << 44)  /* Use opcode::u.fastop */

#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 DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
@@ -1077,7 +1078,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, 
	ctxt->modrm_rm |= (ctxt->modrm & 0x07);

	ctxt->modrm_seg = VCPU_SREG_DS;



	if (ctxt->modrm_mod == 3) {

	if (ctxt->modrm_mod == 3 || (ctxt->d & NoMod)) {

		op->type = OP_REG;

		op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;

		op->addr.reg = decode_register(ctxt, ctxt->modrm_rm,
@@ -3877,10 +3878,12 @@ static const struct opcode twobyte_table[256] = { 
	N, N, N, N, N, N, N, N,

	D(ImplicitOps | ModRM), N, N, N, N, N, N, D(ImplicitOps | ModRM),

	/* 0x20 - 0x2F */

	DIP(ModRM | DstMem | Priv | Op3264, cr_read, check_cr_read),

	DIP(ModRM | DstMem | Priv | Op3264, dr_read, check_dr_read),

	IIP(ModRM | SrcMem | Priv | Op3264, em_cr_write, cr_write, check_cr_write),

	IIP(ModRM | SrcMem | Priv | Op3264, em_dr_write, dr_write, check_dr_write),

	DIP(ModRM | DstMem | Priv | Op3264 | NoMod, cr_read, check_cr_read),

	DIP(ModRM | DstMem | Priv | Op3264 | NoMod, dr_read, check_dr_read),

	IIP(ModRM | SrcMem | Priv | Op3264 | NoMod, em_cr_write, cr_write,

						check_cr_write),

	IIP(ModRM | SrcMem | Priv | Op3264 | NoMod, em_dr_write, dr_write,

						check_dr_write),

	N, N, N, N,

	GP(ModRM | DstReg | SrcMem | Mov | Sse, &pfx_0f_28_0f_29),

	GP(ModRM | DstMem | SrcReg | Mov | Sse, &pfx_0f_28_0f_29),

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