From 9de41573675cbace09b02ef386f3e9c8739d495c Mon Sep 17 00:00:00 2001 From: Gleb Natapov Date: Wed, 28 Apr 2010 19:15:22 +0300 Subject: [PATCH] KVM: x86 emulator: introduce read cache Introduce read cache which is needed for instruction that require more then one exit to userspace. After returning from userspace the instruction will be re-executed with cached read value. Signed-off-by: Gleb Natapov Signed-off-by: Avi Kivity --- arch/x86/include/asm/kvm_emulate.h | 1 + arch/x86/kvm/emulate.c | 56 ++++++++++++++++++++++-------- 2 files changed, 43 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h index 0b2729bf2070..288cbedcab1c 100644 --- a/arch/x86/include/asm/kvm_emulate.h +++ b/arch/x86/include/asm/kvm_emulate.h @@ -186,6 +186,7 @@ struct decode_cache { unsigned long modrm_val; struct fetch_cache fetch; struct read_cache io_read; + struct read_cache mem_read; }; struct x86_emulate_ctxt { diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 5ac0bb465ed6..776874b8e50e 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1263,6 +1263,33 @@ done: return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0; } +static int read_emulated(struct x86_emulate_ctxt *ctxt, + struct x86_emulate_ops *ops, + unsigned long addr, void *dest, unsigned size) +{ + int rc; + struct read_cache *mc = &ctxt->decode.mem_read; + + while (size) { + int n = min(size, 8u); + size -= n; + if (mc->pos < mc->end) + goto read_cached; + + rc = ops->read_emulated(addr, mc->data + mc->end, n, ctxt->vcpu); + if (rc != X86EMUL_CONTINUE) + return rc; + mc->end += n; + + read_cached: + memcpy(dest, mc->data + mc->pos, n); + mc->pos += n; + dest += n; + addr += n; + } + return X86EMUL_CONTINUE; +} + static int pio_in_emulated(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops, unsigned int size, unsigned short port, @@ -1504,9 +1531,9 @@ static int emulate_pop(struct x86_emulate_ctxt *ctxt, struct decode_cache *c = &ctxt->decode; int rc; - rc = ops->read_emulated(register_address(c, ss_base(ctxt), - c->regs[VCPU_REGS_RSP]), - dest, len, ctxt->vcpu); + rc = read_emulated(ctxt, ops, register_address(c, ss_base(ctxt), + c->regs[VCPU_REGS_RSP]), + dest, len); if (rc != X86EMUL_CONTINUE) return rc; @@ -2475,6 +2502,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) int saved_dst_type = c->dst.type; ctxt->interruptibility = 0; + ctxt->decode.mem_read.pos = 0; /* Shadow copy of register state. Committed on successful emulation. * NOTE: we can copy them from vcpu as x86_decode_insn() doesn't @@ -2529,20 +2557,16 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) } if (c->src.type == OP_MEM) { - rc = ops->read_emulated((unsigned long)c->src.ptr, - &c->src.val, - c->src.bytes, - ctxt->vcpu); + rc = read_emulated(ctxt, ops, (unsigned long)c->src.ptr, + &c->src.val, c->src.bytes); if (rc != X86EMUL_CONTINUE) goto done; c->src.orig_val = c->src.val; } if (c->src2.type == OP_MEM) { - rc = ops->read_emulated((unsigned long)c->src2.ptr, - &c->src2.val, - c->src2.bytes, - ctxt->vcpu); + rc = read_emulated(ctxt, ops, (unsigned long)c->src2.ptr, + &c->src2.val, c->src2.bytes); if (rc != X86EMUL_CONTINUE) goto done; } @@ -2553,8 +2577,8 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) if ((c->dst.type == OP_MEM) && !(c->d & Mov)) { /* optimisation - avoid slow emulated read if Mov */ - rc = ops->read_emulated((unsigned long)c->dst.ptr, &c->dst.val, - c->dst.bytes, ctxt->vcpu); + rc = read_emulated(ctxt, ops, (unsigned long)c->dst.ptr, + &c->dst.val, c->dst.bytes); if (rc != X86EMUL_CONTINUE) goto done; } @@ -2981,7 +3005,11 @@ writeback: (rc->end != 0 && rc->end == rc->pos)) ctxt->restart = false; } - + /* + * reset read cache here in case string instruction is restared + * without decoding + */ + ctxt->decode.mem_read.end = 0; /* Commit shadow register state. */ memcpy(ctxt->vcpu->arch.regs, c->regs, sizeof c->regs); kvm_rip_write(ctxt->vcpu, c->eip); -- 2.20.1