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08 Sep 2020 20:57:45 +0000 Received: from EX13MTAUWC002.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan2.iad.amazon.com [10.40.163.34]) by email-inbound-relay-1a-67b371d8.us-east-1.amazon.com (Postfix) with ESMTPS id E8903A1716; Tue, 8 Sep 2020 20:57:41 +0000 (UTC) Received: from EX13D20UWC001.ant.amazon.com (10.43.162.244) by EX13MTAUWC002.ant.amazon.com (10.43.162.240) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 8 Sep 2020 20:57:41 +0000 Received: from u79c5a0a55de558.ant.amazon.com (10.43.160.215) by EX13D20UWC001.ant.amazon.com (10.43.162.244) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 8 Sep 2020 20:57:38 +0000 From: Alexander Graf To: Subject: [PATCH v2] KVM: arm64: Allow to limit number of PMU counters Date: Tue, 8 Sep 2020 22:57:30 +0200 Message-ID: <20200908205730.23898-1-graf@amazon.com> X-Mailer: git-send-email 2.28.0.394.ge197136389 MIME-Version: 1.0 X-Originating-IP: [10.43.160.215] X-ClientProxiedBy: EX13D03UWA002.ant.amazon.com (10.43.160.144) To EX13D20UWC001.ant.amazon.com (10.43.162.244) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200908_165748_647419_A84BFBA8 X-CRM114-Status: GOOD ( 23.97 ) X-Spam-Score: -4.8 (----) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-4.8 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 0.2 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail domains are different -0.0 SPF_PASS SPF: sender matches SPF record 0.0 RCVD_IN_MSPIKE_H3 RBL: Good reputation (+3) [72.21.198.25 listed in wl.mailspike.net] -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [72.21.198.25 listed in list.dnswl.org] 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.0 RCVD_IN_MSPIKE_WL Mailspike good senders -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , kvm@vger.kernel.org, Suzuki K Poulose , Marc Zyngier , Eric Auger , James Morse , linux-arm-kernel@lists.infradead.org, Robin Murphy , Julien Thierry Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org We currently pass through the number of PMU counters that we have available in hardware to guests. So if my host supports 10 concurrently active PMU counters, my guest will be able to spawn 10 counters as well. This is undesireable if we also want to use the PMU on the host for monitoring. In that case, we want to split the PMU between guest and host. To help that case, let's add a PMU attr that allows us to limit the number of PMU counters that we expose. With this patch in place, user space can keep some counters free for host use. Signed-off-by: Alexander Graf --- Because this patch touches the same code paths as the vPMU filtering one and the vPMU filtering generalized a few conditions in the attr path, I've based it on top. Please let me know if you want it independent instead. v1 -> v2: - Add documentation - Add read support --- Documentation/virt/kvm/devices/vcpu.rst | 25 +++++++++++++++++++++++++ arch/arm64/include/uapi/asm/kvm.h | 7 ++++--- arch/arm64/kvm/pmu-emul.c | 32 ++++++++++++++++++++++++++++++++ arch/arm64/kvm/sys_regs.c | 5 +++++ include/kvm/arm_pmu.h | 1 + 5 files changed, 67 insertions(+), 3 deletions(-) diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst index 203b91e93151..1a1c8d8c8b1d 100644 --- a/Documentation/virt/kvm/devices/vcpu.rst +++ b/Documentation/virt/kvm/devices/vcpu.rst @@ -102,6 +102,31 @@ isn't strictly speaking an event. Filtering the cycle counter is possible using event 0x11 (CPU_CYCLES). +1.4 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_NUM_EVENTS +--------------------------------------------- + +:Parameters: in kvm_device_attr.addr the address for the limit of concurrent + events is a pointer to an int + +:Returns: + + ======= ====================================================== + -ENODEV: PMUv3 not supported + -EBUSY: PMUv3 already initialized + -EINVAL: Too large number of events + ======= ====================================================== + +Reconfigure the limit of concurrent PMU events that the guest can monitor. +This number is directly exposed as part of the PMCR_EL0 register. + +On vcpu creation, this attribute is set to the hardware limit of the current +platform. If you need to determine the hardware limit, you can read this +attribute before setting it. + +Restrictions: The default value for this property is the number of hardware +supported events. Only values that are smaller than the hardware limit can +be set. + 2. GROUP: KVM_ARM_VCPU_TIMER_CTRL ================================= diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h index 7b1511d6ce44..db025c0b5a40 100644 --- a/arch/arm64/include/uapi/asm/kvm.h +++ b/arch/arm64/include/uapi/asm/kvm.h @@ -342,9 +342,10 @@ struct kvm_vcpu_events { /* Device Control API on vcpu fd */ #define KVM_ARM_VCPU_PMU_V3_CTRL 0 -#define KVM_ARM_VCPU_PMU_V3_IRQ 0 -#define KVM_ARM_VCPU_PMU_V3_INIT 1 -#define KVM_ARM_VCPU_PMU_V3_FILTER 2 +#define KVM_ARM_VCPU_PMU_V3_IRQ 0 +#define KVM_ARM_VCPU_PMU_V3_INIT 1 +#define KVM_ARM_VCPU_PMU_V3_FILTER 2 +#define KVM_ARM_VCPU_PMU_V3_NUM_EVENTS 3 #define KVM_ARM_VCPU_TIMER_CTRL 1 #define KVM_ARM_VCPU_TIMER_IRQ_VTIMER 0 #define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1 diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index 0458860bade2..c7915b95fec0 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@ -253,6 +253,8 @@ void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) pmu->pmc[i].idx = i; + + pmu->num_events = perf_num_counters() - 1; } /** @@ -978,6 +980,25 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) return 0; } + case KVM_ARM_VCPU_PMU_V3_NUM_EVENTS: { + u64 mask = ARMV8_PMU_PMCR_N_MASK << ARMV8_PMU_PMCR_N_SHIFT; + int __user *uaddr = (int __user *)(long)attr->addr; + u32 num_events; + + if (get_user(num_events, uaddr)) + return -EFAULT; + + if (num_events >= perf_num_counters()) + return -EINVAL; + + vcpu->arch.pmu.num_events = num_events; + + num_events <<= ARMV8_PMU_PMCR_N_SHIFT; + __vcpu_sys_reg(vcpu, SYS_PMCR_EL0) &= ~mask; + __vcpu_sys_reg(vcpu, SYS_PMCR_EL0) |= num_events; + + return 0; + } case KVM_ARM_VCPU_PMU_V3_INIT: return kvm_arm_pmu_v3_init(vcpu); } @@ -1004,6 +1025,16 @@ int kvm_arm_pmu_v3_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) irq = vcpu->arch.pmu.irq_num; return put_user(irq, uaddr); } + case KVM_ARM_VCPU_PMU_V3_NUM_EVENTS: { + int __user *uaddr = (int __user *)(long)attr->addr; + u32 num_events; + + if (!test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features)) + return -ENODEV; + + num_events = vcpu->arch.pmu.num_events; + return put_user(num_events, uaddr); + } } return -ENXIO; @@ -1015,6 +1046,7 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) case KVM_ARM_VCPU_PMU_V3_IRQ: case KVM_ARM_VCPU_PMU_V3_INIT: case KVM_ARM_VCPU_PMU_V3_FILTER: + case KVM_ARM_VCPU_PMU_V3_NUM_EVENTS: if (kvm_arm_support_pmu_v3() && test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features)) return 0; diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 20ab2a7d37ca..d51e39600bbd 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -672,6 +672,11 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) | (ARMV8_PMU_PMCR_MASK & 0xdecafbad)) & (~ARMV8_PMU_PMCR_E); if (!system_supports_32bit_el0()) val |= ARMV8_PMU_PMCR_LC; + + /* Override number of event selectors */ + val &= ~(ARMV8_PMU_PMCR_N_MASK << ARMV8_PMU_PMCR_N_SHIFT); + val |= (u32)vcpu->arch.pmu.num_events << ARMV8_PMU_PMCR_N_SHIFT; + __vcpu_sys_reg(vcpu, r->reg) = val; } diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h index 98cbfe885a53..ea3fc96a37d9 100644 --- a/include/kvm/arm_pmu.h +++ b/include/kvm/arm_pmu.h @@ -27,6 +27,7 @@ struct kvm_pmu { bool ready; bool created; bool irq_level; + u8 num_events; }; #define kvm_arm_pmu_v3_ready(v) ((v)->arch.pmu.ready)