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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id y10-20020a5d4aca000000b0033e03d37685sm12909668wrs.55.2024.03.19.10.58.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 Mar 2024 10:58:34 -0700 (PDT) Message-ID: <84e01fa8-0de6-4d2b-8696-53cd3c3f42fa@redhat.com> Date: Tue, 19 Mar 2024 18:58:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7] arm/kvm: Enable support for KVM_ARM_VCPU_PMU_V3_FILTER Content-Language: en-US To: =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Shaoqin Huang Cc: qemu-arm@nongnu.org, Sebastian Ott , Peter Maydell , Paolo Bonzini , qemu-devel@nongnu.org, kvm@vger.kernel.org References: <20240221063431.76992-1-shahuang@redhat.com> From: Eric Auger In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=eauger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.422, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi Daniel, On 3/19/24 16:22, Daniel P. Berrangé wrote: > On Wed, Feb 21, 2024 at 01:34:31AM -0500, Shaoqin Huang wrote: >> The KVM_ARM_VCPU_PMU_V3_FILTER provides the ability to let the VMM decide >> which PMU events are provided to the guest. Add a new option >> `kvm-pmu-filter` as -cpu sub-option to set the PMU Event Filtering. >> Without the filter, all PMU events are exposed from host to guest by >> default. The usage of the new sub-option can be found from the updated >> document (docs/system/arm/cpu-features.rst). >> >> Here is an example which shows how to use the PMU Event Filtering, when >> we launch a guest by use kvm, add such command line: >> >> # qemu-system-aarch64 \ >> -accel kvm \ >> -cpu host,kvm-pmu-filter="D:0x11-0x11" > > snip > >> @@ -517,6 +533,12 @@ void kvm_arm_add_vcpu_properties(ARMCPU *cpu) >> kvm_steal_time_set); >> object_property_set_description(obj, "kvm-steal-time", >> "Set off to disable KVM steal time."); >> + >> + object_property_add_str(obj, "kvm-pmu-filter", kvm_pmu_filter_get, >> + kvm_pmu_filter_set); >> + object_property_set_description(obj, "kvm-pmu-filter", >> + "PMU Event Filtering description for " >> + "guest PMU. (default: NULL, disabled)"); >> } > > Passing a string property, but....[1] > >> >> bool kvm_arm_pmu_supported(void) >> @@ -1706,6 +1728,62 @@ static bool kvm_arm_set_device_attr(ARMCPU *cpu, struct kvm_device_attr *attr, >> return true; >> } >> >> +static void kvm_arm_pmu_filter_init(ARMCPU *cpu) >> +{ >> + static bool pmu_filter_init; >> + struct kvm_pmu_event_filter filter; >> + struct kvm_device_attr attr = { >> + .group = KVM_ARM_VCPU_PMU_V3_CTRL, >> + .attr = KVM_ARM_VCPU_PMU_V3_FILTER, >> + .addr = (uint64_t)&filter, >> + }; >> + int i; >> + g_auto(GStrv) event_filters; >> + >> + if (!cpu->kvm_pmu_filter) { >> + return; >> + } >> + if (kvm_vcpu_ioctl(CPU(cpu), KVM_HAS_DEVICE_ATTR, &attr)) { >> + warn_report("The KVM doesn't support the PMU Event Filter!"); > > If the user requested a filter and it can't be supported, QEMU > must exit with an error, not ignore the user's request. > >> + return; >> + } >> + >> + /* >> + * The filter only needs to be initialized through one vcpu ioctl and it >> + * will affect all other vcpu in the vm. >> + */ >> + if (pmu_filter_init) { >> + return; >> + } else { >> + pmu_filter_init = true; >> + } >> + >> + event_filters = g_strsplit(cpu->kvm_pmu_filter, ";", -1); >> + for (i = 0; event_filters[i]; i++) { >> + unsigned short start = 0, end = 0; >> + char act; >> + >> + if (sscanf(event_filters[i], "%c:%hx-%hx", &act, &start, &end) != 3) { >> + warn_report("Skipping invalid PMU filter %s", event_filters[i]); >> + continue; > > Warning on user syntax errors is undesirable - it should be a fatal > error of the user gets this wrong. > >> + } >> + >> + if ((act != 'A' && act != 'D') || start > end) { >> + warn_report("Skipping invalid PMU filter %s", event_filters[i]); >> + continue; > > Likewise should be fatal. > >> + } >> + >> + filter.base_event = start; >> + filter.nevents = end - start + 1; >> + filter.action = (act == 'A') ? KVM_PMU_EVENT_ALLOW : >> + KVM_PMU_EVENT_DENY; >> + >> + if (!kvm_arm_set_device_attr(cpu, &attr, "PMU_V3_FILTER")) { >> + break; >> + } >> + } >> +} > > ..[1] then implementing a custom parser is rather a QEMU design anti-pattern, > especially when the proposed syntax is incapable of being mapped into the > normal QAPI syntax for a list of structs should we want to fully convert > -cpu to QAPI parsing later. I wonder if can we model this property with > QAPI now ? I guess you mean creating a new property like those in hw/core/qdev-properties-system.c for instance and populating an array of those at CPU object level? Note there is v8 but most of your comments still apply https://lore.kernel.org/all/20240312074849.71475-1-shahuang@redhat.com/ Thanks Eric > > With regards, > Daniel