From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755667AbcIFLeJ (ORCPT ); Tue, 6 Sep 2016 07:34:09 -0400 Received: from fw-tnat.cambridge.arm.com ([217.140.96.140]:52024 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752958AbcIFLeH (ORCPT ); Tue, 6 Sep 2016 07:34:07 -0400 From: Punit Agrawal To: Christoffer Dall Cc: kvm@vger.kernel.org, Marc Zyngier , Will Deacon , linux-kernel@vger.kernel.org, Steven Rostedt , Ingo Molnar , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC v2 PATCH 7/7] arm64: KVM: Enable selective trapping of TLB instructions References: <1473093097-30932-1-git-send-email-punit.agrawal@arm.com> <1473093097-30932-8-git-send-email-punit.agrawal@arm.com> <20160906102404.GF30513@cbox> Date: Tue, 06 Sep 2016 12:33:29 +0100 In-Reply-To: <20160906102404.GF30513@cbox> (Christoffer Dall's message of "Tue, 6 Sep 2016 12:24:04 +0200") Message-ID: <871t0xjm9i.fsf@e105922-lin.cambridge.arm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christoffer Dall writes: > On Mon, Sep 05, 2016 at 05:31:37PM +0100, Punit Agrawal wrote: >> The TTLB bit of Hypervisor Control Register (HCR_EL2) controls the >> trapping of guest TLB maintenance instructions. Taking the trap requires >> a switch to the hypervisor and is an expensive operation. >> >> Enable selective trapping of guest TLB instructions when the associated >> perf trace event is enabled for a specific virtual machine. >> >> Signed-off-by: Punit Agrawal >> Cc: Christoffer Dall >> Cc: Marc Zyngier >> --- >> arch/arm64/kvm/perf_trace.c | 32 ++++++++++++++++++++++++++++++++ >> 1 file changed, 32 insertions(+) >> >> diff --git a/arch/arm64/kvm/perf_trace.c b/arch/arm64/kvm/perf_trace.c >> index 8bacd18..f26da1d 100644 >> --- a/arch/arm64/kvm/perf_trace.c >> +++ b/arch/arm64/kvm/perf_trace.c >> @@ -17,6 +17,8 @@ >> #include >> #include >> >> +#include >> + >> typedef int (*perf_trace_callback_fn)(struct kvm *kvm, bool enable); >> >> struct kvm_trace_hook { >> @@ -24,7 +26,37 @@ struct kvm_trace_hook { >> perf_trace_callback_fn setup_fn; >> }; >> >> +static int tlb_invalidate_trap(struct kvm *kvm, bool enable) >> +{ >> + int i; >> + struct kvm_vcpu *vcpu; >> + >> + /* >> + * Halt the VM to ensure atomic update across all vcpus (this >> + * avoids racy behaviour against other modifications of >> + * HCR_EL2 such as kvm_toggle_cache/kvm_set_way_flush). >> + */ >> + kvm_arm_halt_guest(kvm); >> + kvm_for_each_vcpu(i, vcpu, kvm) { >> + unsigned long hcr = vcpu_get_hcr(vcpu); >> + >> + if (enable) >> + hcr |= HCR_TTLB; >> + else >> + hcr &= ~HCR_TTLB; >> + >> + vcpu_set_hcr(vcpu, hcr); >> + } >> + kvm_arm_resume_guest(kvm); >> + >> + return 0; >> +} >> + >> static struct kvm_trace_hook trace_hook[] = { >> + { >> + .key = "kvm_tlb_invalidate", > > is this key defined elsewhere? If not, I think the name is ambiguous, > because it's unclear if this means 'kvm the subsystem' or 'a kvm guest', > by looking purely at the string. The key is the name of the tracepoint that the callback is executed against. Here it is the tracepoint defined in Patch 6/7. I've now added a comment to the definition of "struct kvm_trace_hook" to explain what the key is. > >> + .setup_fn = tlb_invalidate_trap, >> + }, >> { }, >> }; >> >> -- >> 2.8.1 >> > > Otherwise looks ok to me. > > -Christoffer > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm