From d40a6898e50c2589ca3d345ef5ca6671e2b35b1a Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 27 Mar 2014 11:58:02 +0100 Subject: [PATCH] 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: Paolo Bonzini --- arch/x86/kvm/emulate.c | 175 ++++++++++++++++++++++------------------- 1 file changed, 94 insertions(+), 81 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index d79677c6056d..ea56dae3e67c 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -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) @@ -4393,29 +4395,37 @@ done_prefixes: return EMULATION_FAILED; ctxt->execute = opcode.u.execute; - ctxt->check_perm = opcode.check_perm; - ctxt->intercept = opcode.intercept; - if (ctxt->d & NotImpl) - return EMULATION_FAILED; + 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; - if (!(ctxt->d & EmulateOnUD) && ctxt->ud) - return EMULATION_FAILED; + if (ctxt->d & NotImpl) + return EMULATION_FAILED; - if (mode == X86EMUL_MODE_PROT64 && (ctxt->d & Stack)) - ctxt->op_bytes = 8; + if (!(ctxt->d & EmulateOnUD) && ctxt->ud) + return EMULATION_FAILED; - if (ctxt->d & Op3264) { - if (mode == X86EMUL_MODE_PROT64) + if (mode == X86EMUL_MODE_PROT64 && (ctxt->d & Stack)) ctxt->op_bytes = 8; - else - ctxt->op_bytes = 4; - } - if (ctxt->d & Sse) - ctxt->op_bytes = 16; - else if (ctxt->d & Mmx) - ctxt->op_bytes = 8; + if (ctxt->d & Op3264) { + if (mode == X86EMUL_MODE_PROT64) + ctxt->op_bytes = 8; + else + ctxt->op_bytes = 4; + } + + if (ctxt->d & Sse) + ctxt->op_bytes = 16; + else if (ctxt->d & Mmx) + ctxt->op_bytes = 8; + } /* ModRM and SIB bytes. */ if (ctxt->d & ModRM) { @@ -4549,75 +4559,78 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) goto done; } - if ((ctxt->mode == X86EMUL_MODE_PROT64 && (ctxt->d & No64)) || - (ctxt->d & Undefined)) { - rc = emulate_ud(ctxt); - goto done; - } - - if (((ctxt->d & (Sse|Mmx)) && ((ops->get_cr(ctxt, 0) & X86_CR0_EM))) - || ((ctxt->d & Sse) && !(ops->get_cr(ctxt, 4) & X86_CR4_OSFXSR))) { - rc = emulate_ud(ctxt); - goto done; - } - - if ((ctxt->d & (Sse|Mmx)) && (ops->get_cr(ctxt, 0) & X86_CR0_TS)) { - rc = emulate_nm(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); + goto done; + } - if (ctxt->d & Mmx) { - rc = flush_pending_x87_faults(ctxt); - if (rc != X86EMUL_CONTINUE) + if (((ctxt->d & (Sse|Mmx)) && ((ops->get_cr(ctxt, 0) & X86_CR0_EM))) + || ((ctxt->d & Sse) && !(ops->get_cr(ctxt, 4) & X86_CR4_OSFXSR))) { + rc = emulate_ud(ctxt); goto done; - /* - * Now that we know the fpu is exception safe, we can fetch - * operands from it. - */ - fetch_possible_mmx_operand(ctxt, &ctxt->src); - fetch_possible_mmx_operand(ctxt, &ctxt->src2); - if (!(ctxt->d & Mov)) - fetch_possible_mmx_operand(ctxt, &ctxt->dst); - } + } - if (unlikely(ctxt->guest_mode) && ctxt->intercept) { - rc = emulator_check_intercept(ctxt, ctxt->intercept, - X86_ICPT_PRE_EXCEPT); - if (rc != X86EMUL_CONTINUE) + if ((ctxt->d & (Sse|Mmx)) && (ops->get_cr(ctxt, 0) & X86_CR0_TS)) { + rc = emulate_nm(ctxt); goto done; - } + } - /* Privileged instruction can be executed only in CPL=0 */ - if ((ctxt->d & Priv) && ops->cpl(ctxt)) { - rc = emulate_gp(ctxt, 0); - goto done; - } + if (ctxt->d & Mmx) { + rc = flush_pending_x87_faults(ctxt); + if (rc != X86EMUL_CONTINUE) + goto done; + /* + * Now that we know the fpu is exception safe, we can fetch + * operands from it. + */ + fetch_possible_mmx_operand(ctxt, &ctxt->src); + fetch_possible_mmx_operand(ctxt, &ctxt->src2); + if (!(ctxt->d & Mov)) + fetch_possible_mmx_operand(ctxt, &ctxt->dst); + } - /* Instruction can only be executed in protected mode */ - if ((ctxt->d & Prot) && ctxt->mode < X86EMUL_MODE_PROT16) { - rc = emulate_ud(ctxt); - goto done; - } + if (unlikely(ctxt->guest_mode) && ctxt->intercept) { + rc = emulator_check_intercept(ctxt, ctxt->intercept, + X86_ICPT_PRE_EXCEPT); + if (rc != X86EMUL_CONTINUE) + goto done; + } - /* Do instruction specific permission checks */ - if (ctxt->check_perm) { - rc = ctxt->check_perm(ctxt); - if (rc != X86EMUL_CONTINUE) + /* Privileged instruction can be executed only in CPL=0 */ + if ((ctxt->d & Priv) && ops->cpl(ctxt)) { + rc = emulate_gp(ctxt, 0); goto done; - } + } - if (unlikely(ctxt->guest_mode) && ctxt->intercept) { - rc = emulator_check_intercept(ctxt, ctxt->intercept, - X86_ICPT_POST_EXCEPT); - if (rc != X86EMUL_CONTINUE) + /* Instruction can only be executed in protected mode */ + if ((ctxt->d & Prot) && ctxt->mode < X86EMUL_MODE_PROT16) { + rc = emulate_ud(ctxt); goto done; - } + } - if (ctxt->rep_prefix && (ctxt->d & String)) { - /* All REP prefixes have the same first termination condition */ - if (address_mask(ctxt, reg_read(ctxt, VCPU_REGS_RCX)) == 0) { - ctxt->eip = ctxt->_eip; - goto done; + /* Do instruction specific permission checks */ + if (ctxt->check_perm) { + rc = ctxt->check_perm(ctxt); + if (rc != X86EMUL_CONTINUE) + goto done; + } + + if (unlikely(ctxt->guest_mode) && ctxt->intercept) { + rc = emulator_check_intercept(ctxt, ctxt->intercept, + X86_ICPT_POST_EXCEPT); + if (rc != X86EMUL_CONTINUE) + goto done; + } + + if (ctxt->rep_prefix && (ctxt->d & String)) { + /* All REP prefixes have the same first termination condition */ + if (address_mask(ctxt, reg_read(ctxt, VCPU_REGS_RCX)) == 0) { + ctxt->eip = ctxt->_eip; + goto done; + } } } -- 2.39.5