From 0d7cdee83ad1582eecbf3b4a220e82dcb5ad561c Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Tue, 29 Mar 2011 11:34:38 +0200 Subject: [PATCH] KVM: x86 emulator: Specialize decoding for insns with 66/f2/f3 prefixes Most SIMD instructions use the 66/f2/f3 prefixes to distinguish between different variants of the same instruction. Usually the encoding is quite regular, but in some cases (including non-SIMD instructions) the prefixes generate very different instructions. Examples include XCHG/PAUSE, MOVQ/MOVDQA/MOVDQU, and MOVBE/CRC32. Allow the emulator to handle these special cases by splitting such opcodes into groups, with different decode flags and execution functions for different prefixes. Signed-off-by: Avi Kivity --- arch/x86/kvm/emulate.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 075bb6fc73a..fcce7aeacc8 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -75,6 +75,7 @@ #define Stack (1<<13) /* Stack instruction (push/pop) */ #define Group (1<<14) /* Bits 3:5 of modrm byte extend opcode */ #define GroupDual (1<<15) /* Alternate decoding of mod == 3 */ +#define Prefix (1<<16) /* Instruction varies with 66/f2/f3 prefix */ /* Misc flags */ #define VendorSpecific (1<<22) /* Vendor specific instruction */ #define NoAccess (1<<23) /* Don't access memory (lea/invlpg/verr etc) */ @@ -106,6 +107,7 @@ struct opcode { int (*execute)(struct x86_emulate_ctxt *ctxt); struct opcode *group; struct group_dual *gdual; + struct gprefix *gprefix; } u; }; @@ -114,6 +116,13 @@ struct group_dual { struct opcode mod3[8]; }; +struct gprefix { + struct opcode pfx_no; + struct opcode pfx_66; + struct opcode pfx_f2; + struct opcode pfx_f3; +}; + /* EFLAGS bit definitions. */ #define EFLG_ID (1<<21) #define EFLG_VIP (1<<20) @@ -2625,7 +2634,8 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) struct decode_cache *c = &ctxt->decode; int rc = X86EMUL_CONTINUE; int mode = ctxt->mode; - int def_op_bytes, def_ad_bytes, dual, goffset; + int def_op_bytes, def_ad_bytes, dual, goffset, simd_prefix; + bool op_prefix = false; struct opcode opcode, *g_mod012, *g_mod3; struct operand memop = { .type = OP_NONE }; @@ -2662,6 +2672,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) for (;;) { switch (c->b = insn_fetch(u8, 1, c->eip)) { case 0x66: /* operand-size override */ + op_prefix = true; /* switch between 2/4 bytes */ c->op_bytes = def_op_bytes ^ 6; break; @@ -2742,6 +2753,19 @@ done_prefixes: c->d |= opcode.flags; } + if (c->d & Prefix) { + if (c->rep_prefix && op_prefix) + return X86EMUL_UNHANDLEABLE; + simd_prefix = op_prefix ? 0x66 : c->rep_prefix; + switch (simd_prefix) { + case 0x00: opcode = opcode.u.gprefix->pfx_no; break; + case 0x66: opcode = opcode.u.gprefix->pfx_66; break; + case 0xf2: opcode = opcode.u.gprefix->pfx_f2; break; + case 0xf3: opcode = opcode.u.gprefix->pfx_f3; break; + } + c->d |= opcode.flags; + } + c->execute = opcode.u.execute; /* Unrecognised? */ -- 2.41.0