From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCHv4 5/5] KVM: Provide fast path for "rep ins" emulation if possible. Date: Thu, 19 Jul 2012 13:37:32 +0300 Message-ID: <5007E36C.6000807@redhat.com> References: <1342683653-32114-1-git-send-email-gleb@redhat.com> <1342683653-32114-6-git-send-email-gleb@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, mtosatti@redhat.com To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:1086 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751701Ab2GSKhf (ORCPT ); Thu, 19 Jul 2012 06:37:35 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q6JAbZFC024435 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 19 Jul 2012 06:37:35 -0400 In-Reply-To: <1342683653-32114-6-git-send-email-gleb@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/19/2012 10:40 AM, Gleb Natapov wrote: > "rep ins" emulation is going through emulator now. This is slow because > emulator knows how to write back only one datum at a time. This patch > provides fast path for the instruction in certain conditions. The > conditions are: DF flag is not set, destination memory is RAM and single > datum does not cross page boundary. If fast path code fails it falls > back to emulation. > > + > +int kvm_fast_string_pio_in(struct kvm_vcpu *vcpu, int size, > + unsigned short port, u8 ad_bytes_idx) > +{ > + unsigned long rdi = kvm_register_read(vcpu, VCPU_REGS_RDI); > + unsigned long linear_addr; > + unsigned long rcx = kvm_register_read(vcpu, VCPU_REGS_RCX), count; > + u8 ad_bytes; > + int r; > + > + if (ad_bytes_idx > 2) > + return EMULATE_FAIL; > + > + ad_bytes = (u8[]){2, 4, 8}[ad_bytes_idx]; > + 2 << logs2_ad_bytes instead of this nice functional programming style. > + rcx = kvm_address_mask(ad_bytes, rcx); > + > + if (rcx == 0) { > + kvm_x86_ops->skip_emulated_instruction(vcpu); > + return EMULATE_DONE; > + } > + > + if (kvm_get_rflags(vcpu) & X86_EFLAGS_DF) > + return EMULATE_FAIL; > + > + rdi = kvm_address_mask(ad_bytes, rdi); > + > + r = kvm_linearize_address(vcpu, get_emulation_mode(vcpu), > + rdi, VCPU_SREG_ES, rcx * size, true, false, ad_bytes, > + &linear_addr); > + > + if (r >= 0) > + return EMULATE_FAIL; > + > + count = (PAGE_SIZE - offset_in_page(linear_addr))/size; > + > + if (count == 0) /* 'in' crosses page boundry */ > + return EMULATE_FAIL; > + > + count = min(count, rcx); > + > + r = __kvm_fast_string_pio_in(vcpu, size, port, linear_addr, count); > + > + if (r != EMULATE_DO_MMIO) > + return r; > + > + vcpu->arch.fast_string_pio_ctxt.linear_addr = linear_addr; > + vcpu->arch.fast_string_pio_ctxt.ad_bytes = ad_bytes; > + vcpu->arch.complete_userspace_io = complete_fast_string_pio; > + return EMULATE_DO_MMIO; > +} > +EXPORT_SYMBOL_GPL(kvm_fast_string_pio_in); > + -- error compiling committee.c: too many arguments to function