memory_prepare lets us replace segmented_read/segmented_write with direct calls to __copy_from_user/__copy_to_user. For RMW instructions, we also avoid double walking of the page tables.
This saves about 50 cycles (5%) on arithmetic with a memory source operand, and up to 300 cycles (20%) on arithmetic with a memory destination operand. Reviewed-by: Marcelo Tosatti <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> --- arch/x86/include/asm/kvm_emulate.h | 2 ++ arch/x86/kvm/emulate.c | 72 +++++++++++++++++++++++++++++++++++--- 2 files changed, 69 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h index 1aa2adf0bb1a..f596976a3ab2 100644 --- a/arch/x86/include/asm/kvm_emulate.h +++ b/arch/x86/include/asm/kvm_emulate.h @@ -263,6 +263,8 @@ struct operand { u64 mm_val; void *data; }; + unsigned long hva; + void *opaque; }; struct fetch_cache { diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 7e9dc2d6fd44..594cb560947c 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1260,6 +1260,29 @@ read_cached: return X86EMUL_CONTINUE; } +static int read_from_user(struct x86_emulate_ctxt *ctxt, + unsigned long hva, void *dest, unsigned size) +{ + int rc; + struct read_cache *mc = &ctxt->mem_read; + + if (mc->pos < mc->end) + goto read_cached; + + WARN_ON((mc->end + size) >= sizeof(mc->data)); + + rc = __copy_from_user(mc->data + mc->end, (void __user *)hva, size); + if (rc < 0) + return X86EMUL_UNHANDLEABLE; + + mc->end += size; + +read_cached: + memcpy(dest, mc->data + mc->pos, size); + mc->pos += size; + return X86EMUL_CONTINUE; +} + static int segmented_read(struct x86_emulate_ctxt *ctxt, struct segmented_address addr, void *data, @@ -1565,9 +1588,36 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt, } static int prepare_memory_operand(struct x86_emulate_ctxt *ctxt, - struct operand *op) + struct operand *op, + bool write) { - return segmented_read(ctxt, op->addr.mem, &op->val, op->bytes); + int rc; + unsigned long gva; + unsigned int size = op->bytes; + + rc = linearize(ctxt, op->addr.mem, size, write, &gva); + if (rc != X86EMUL_CONTINUE) + return rc; + + rc = ctxt->ops->memory_prepare(ctxt, gva, size, + &ctxt->exception, true, + &op->opaque, &op->hva); + if (rc != X86EMUL_CONTINUE) + return rc; + + if (likely(!kvm_is_error_hva(op->hva))) { + rc = read_from_user(ctxt, op->hva, &op->val, size); + if (!write) + ctxt->ops->memory_finish(ctxt, op->opaque, op->hva); + + if (likely(rc == X86EMUL_CONTINUE)) + return X86EMUL_CONTINUE; + + /* Should not happen. */ + op->hva = KVM_HVA_ERR_BAD; + } + + return read_emulated(ctxt, gva, &op->val, size); } static int cmpxchg_memory_operand(struct x86_emulate_ctxt *ctxt, @@ -1582,6 +1632,17 @@ static int cmpxchg_memory_operand(struct x86_emulate_ctxt *ctxt, static int write_memory_operand(struct x86_emulate_ctxt *ctxt, struct operand *op) { + int rc; + + if (likely(!kvm_is_error_hva(op->hva))) { + rc = __copy_to_user((void __user *)op->hva, &op->val, + op->bytes); + ctxt->ops->memory_finish(ctxt, op->opaque, op->hva); + + if (likely(!rc)) + return X86EMUL_CONTINUE; + } + return segmented_write(ctxt, op->addr.mem, &op->val, op->bytes); @@ -4638,14 +4699,14 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) } if ((ctxt->src.type == OP_MEM) && !(ctxt->d & NoAccess)) { - rc = prepare_memory_operand(ctxt, &ctxt->src); + rc = prepare_memory_operand(ctxt, &ctxt->src, false); if (rc != X86EMUL_CONTINUE) goto done; ctxt->src.orig_val64 = ctxt->src.val64; } if (ctxt->src2.type == OP_MEM) { - rc = prepare_memory_operand(ctxt, &ctxt->src2); + rc = prepare_memory_operand(ctxt, &ctxt->src2, false); if (rc != X86EMUL_CONTINUE) goto done; } @@ -4656,7 +4717,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) if ((ctxt->dst.type == OP_MEM) && !(ctxt->d & Mov)) { /* optimisation - avoid slow emulated read if Mov */ - rc = prepare_memory_operand(ctxt, &ctxt->dst); + rc = prepare_memory_operand(ctxt, &ctxt->dst, + !(ctxt->d & NoWrite)); if (rc != X86EMUL_CONTINUE) goto done; } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
