From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: ioeventfd usage in KVM Date: Fri, 12 Mar 2010 18:43:38 +0200 Message-ID: <4B9A6F3A.8080507@redhat.com> References: <8286e4ee1003112108j4a3a477dq4abb1b8624319125@mail.gmail.com> <4B99F0B1.6050606@redhat.com> <8286e4ee1003120750g5aad52a2se6a9bd0796984c7c@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: KVM General To: Cam Macdonell Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50435 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758626Ab0CLQnm (ORCPT ); Fri, 12 Mar 2010 11:43:42 -0500 In-Reply-To: <8286e4ee1003120750g5aad52a2se6a9bd0796984c7c@mail.gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/12/2010 05:50 PM, Cam Macdonell wrote: > >> Yes - they must match. Not PIO is faster on x86 but nonexistant elsewhere. >> > s/Not/Note/. > Does it matter that PIO is slower since with ioeventfd Qemu is being > bypassed all together? mmio is slower in kvm, not qemu; mmio must go through the emulator, fetch the instruction, decode and execute it, while pio decoding is done by the processor microcode. > Can I use the memory space with ioeventfds? > Yes. > There doesn't seem to be a flag (KVM_IOEVENTFD_FLAG_MMIO) for it. > If you don't specify _PIO, _MMIO is the default, as Documentation/kvm/api.txt doesn't say. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.