Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753317AbbH3JMy (ORCPT ); Sun, 30 Aug 2015 05:12:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49227 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751701AbbH3JMr (ORCPT ); Sun, 30 Aug 2015 05:12:47 -0400 Date: Sun, 30 Aug 2015 12:12:44 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, Paolo Bonzini Subject: [PATCH RFC 1/3] vmx: allow ioeventfd for EPT violations Message-ID: <1440925898-23440-2-git-send-email-mst@redhat.com> References: <1440925898-23440-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1440925898-23440-1-git-send-email-mst@redhat.com> X-Mutt-Fcc: =sent Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1380 Lines: 42 Even when we skip data decoding, MMIO is slightly slower than port IO because it uses the page-tables, so the CPU must do a pagewalk on each access. This overhead is normally masked by using the TLB cache: but not so for KVM MMIO, where PTEs are marked as reserved and so are never cached. As ioeventfd memory is never read, make it possible to use RO pages on the host for ioeventfds, instead. The result is that TLBs are cached, which finally makes MMIO as fast as port IO. Signed-off-by: Michael S. Tsirkin --- arch/x86/kvm/vmx.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 9d1bfd3..ed44026 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -5745,6 +5745,11 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu) vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO, GUEST_INTR_STATE_NMI); gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS); + if (!kvm_io_bus_write(vcpu, KVM_FAST_MMIO_BUS, gpa, 0, NULL)) { + skip_emulated_instruction(vcpu); + return 1; + } + trace_kvm_page_fault(gpa, exit_qualification); /* It is a write fault? */ -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/