Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753366AbbH3JM4 (ORCPT ); Sun, 30 Aug 2015 05:12:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33101 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218AbbH3JMu (ORCPT ); Sun, 30 Aug 2015 05:12:50 -0400 Date: Sun, 30 Aug 2015 12:12:47 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, Paolo Bonzini Subject: [PATCH RFC 2/3] svm: allow ioeventfd for NPT page faults Message-ID: <1440925898-23440-3-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: 1406 Lines: 43 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. Warning: untested. Signed-off-by: Michael S. Tsirkin --- arch/x86/kvm/svm.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 8e0c084..6422fac 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1812,6 +1812,11 @@ static int pf_interception(struct vcpu_svm *svm) switch (svm->apf_reason) { default: error_code = svm->vmcb->control.exit_info_1; + if (!kvm_io_bus_write(&svm->vcpu, KVM_FAST_MMIO_BUS, + fault_address, 0, NULL)) { + skip_emulated_instruction(&svm->vcpu); + return 1; + } trace_kvm_page_fault(fault_address, error_code); if (!npt_enabled && kvm_event_needs_reinjection(&svm->vcpu)) -- 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/