From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753453AbcHPKqQ (ORCPT ); Tue, 16 Aug 2016 06:46:16 -0400 Received: from fw-tnat.cambridge.arm.com ([217.140.96.140]:57182 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753258AbcHPKqO (ORCPT ); Tue, 16 Aug 2016 06:46:14 -0400 From: Punit Agrawal To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Cc: Punit Agrawal , Christoffer Dall , Marc Zyngier , Steven Rostedt , Ingo Molnar , Will Deacon Subject: [RFC PATCH 0/7] Add support for monitoring guest TLB operations Date: Tue, 16 Aug 2016 11:45:05 +0100 Message-Id: <1471344312-26685-1-git-send-email-punit.agrawal@arm.com> X-Mailer: git-send-email 2.8.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, ARMv8 supports trapping guest TLB maintenance operations to the hypervisor. This trapping mechanism can be used to monitor the use of guest TLB instructions. As taking a trap for every TLB operation can have significant overhead, trapping should only be enabled - * on user request * for the VM of interest This patchset adds support to listen to perf trace event state change notifications. The notifications and associated context are then used to enable trapping of guest TLB operations when requested by the user. The trap handling generates trace events (kvm_tlb_invalidate) which can already be counted using existing perf trace functionality. Trapping of guest TLB operations is disabled when not being monitored (reducing profiling overhead). I would appreciate feedback on the approach to tie the control of TLB monitoring with perf trace events (Patch 1) especially if there are any suggestions on avoiding (or reducing) the overhead of "perf trace" notifications. I looked at using regfunc/unregfunc tracepoint hooks but they don't include the event context. But the bigger problem was that the callbacks are only called on the first instance of simultaneously executing perf stat invocations. The patchset is based on v4.8-rc2 and adds support for monitoring guest TLB operations on 64bit hosts. If the approach taken in the patches is acceptable, I'll add 32bit host support as well. With this patchset, 'perf' tool when attached to a VM process can be used to monitor the TLB operations. E.g., to monitor a VM with process id 4166 - # perf stat -e "kvm:kvm_tlb_invalidate" -p 4166 Perform some operations in VM (running 'make -j 7' on the kernel sources in this instance). Breaking out of perf shows - Performance counter stats for process id '4166': 7,471,974 kvm:kvm_tlb_invalidate 374.235405282 seconds time elapsed All feedback welcome. Thanks, Punit Mark Rutland (2): arm64: tlbflush.h: add __tlbi() macro arm64/kvm: hyp: tlb: use __tlbi() helper Punit Agrawal (5): perf/trace: Add notification for perf trace events KVM: Track the pid of the VM process KVM: arm/arm64: Register perf trace event notifier arm64: KVM: Handle trappable TLB instructions arm64: KVM: Enable selective trapping of TLB instructions arch/arm/include/asm/kvm_host.h | 3 + arch/arm/kvm/arm.c | 2 + arch/arm64/include/asm/kvm_asm.h | 1 + arch/arm64/include/asm/kvm_host.h | 8 ++ arch/arm64/include/asm/tlbflush.h | 31 ++++++-- arch/arm64/kvm/Kconfig | 4 + arch/arm64/kvm/Makefile | 1 + arch/arm64/kvm/hyp/tlb.c | 158 ++++++++++++++++++++++++++++++++++++-- arch/arm64/kvm/perf_trace.c | 154 +++++++++++++++++++++++++++++++++++++ arch/arm64/kvm/sys_regs.c | 81 +++++++++++++++++++ arch/arm64/kvm/trace.h | 16 ++++ include/linux/kvm_host.h | 1 + include/linux/trace_events.h | 3 + kernel/trace/trace_event_perf.c | 24 ++++++ virt/kvm/kvm_main.c | 2 + 15 files changed, 475 insertions(+), 14 deletions(-) create mode 100644 arch/arm64/kvm/perf_trace.c -- 2.8.1