From patchwork Mon Jan 27 14:17:23 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13951434 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 26660C02188 for ; Mon, 27 Jan 2025 14:20:36 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tcPxM-0000AG-3M; Mon, 27 Jan 2025 09:19:16 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcPxJ-00009E-UR; Mon, 27 Jan 2025 09:19:13 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcPxH-0002Po-TD; Mon, 27 Jan 2025 09:19:13 -0500 Received: from localhost.tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by isrv.corpit.ru (Postfix) with ESMTP id 495ACE0E35; Mon, 27 Jan 2025 17:18:40 +0300 (MSK) Received: by localhost.tls.msk.ru (Postfix, from userid 1000) id 6F54151D74; Mon, 27 Jan 2025 17:18:03 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, "Maciej S. Szmigiero" , Paolo Bonzini , Michael Tokarev Subject: [Stable-9.2.1 09/41] target/i386: Reset TSCs of parked vCPUs too on VM reset Date: Mon, 27 Jan 2025 17:17:23 +0300 Message-Id: <20250127141803.3514882-9-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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 From: "Maciej S. Szmigiero" Since commit 5286c3662294 ("target/i386: properly reset TSC on reset") QEMU writes the special value of "1" to each online vCPU TSC on VM reset to reset it. However parked vCPUs don't get that handling and due to that their TSCs get desynchronized when the VM gets reset. This in turn causes KVM to turn off PVCLOCK_TSC_STABLE_BIT in its exported PV clock. Note that KVM has no understanding of vCPU being currently parked. Without PVCLOCK_TSC_STABLE_BIT the sched clock is marked unstable in the guest's kvm_sched_clock_init(). This causes a performance regressions to show in some tests. Fix this issue by writing the special value of "1" also to TSCs of parked vCPUs on VM reset. Reproducing the issue: 1) Boot a VM with "-smp 2,maxcpus=3" or similar 2) device_add host-x86_64-cpu,id=vcpu,node-id=0,socket-id=0,core-id=2,thread-id=0 3) Wait a few seconds 4) device_del vcpu 5) Inside the VM run: # echo "t" >/proc/sysrq-trigger; dmesg | grep sched_clock_stable Observe the sched_clock_stable() value is 1. 6) Reboot the VM 7) Once the VM boots once again run inside it: # echo "t" >/proc/sysrq-trigger; dmesg | grep sched_clock_stable Observe the sched_clock_stable() value is now 0. Fixes: 5286c3662294 ("target/i386: properly reset TSC on reset") Signed-off-by: Maciej S. Szmigiero Link: https://lore.kernel.org/r/5a605a88e9a231386dc803c60f5fed9b48108139.1734014926.git.maciej.szmigiero@oracle.com Signed-off-by: Paolo Bonzini (cherry picked from commit 3f2a05b31ee9ce2ddb6c75a9bc3f5e7f7af9a76f) Signed-off-by: Michael Tokarev diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 801cff16a5..dec1d1c16a 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -437,6 +437,16 @@ int kvm_unpark_vcpu(KVMState *s, unsigned long vcpu_id) return kvm_fd; } +static void kvm_reset_parked_vcpus(void *param) +{ + KVMState *s = param; + struct KVMParkedVcpu *cpu; + + QLIST_FOREACH(cpu, &s->kvm_parked_vcpus, node) { + kvm_arch_reset_parked_vcpu(cpu->vcpu_id, cpu->kvm_fd); + } +} + int kvm_create_vcpu(CPUState *cpu) { unsigned long vcpu_id = kvm_arch_vcpu_id(cpu); @@ -2728,6 +2738,7 @@ static int kvm_init(MachineState *ms) } qemu_register_reset(kvm_unpoison_all, NULL); + qemu_register_reset(kvm_reset_parked_vcpus, s); if (s->kernel_irqchip_allowed) { kvm_irqchip_create(s); diff --git a/configs/targets/i386-softmmu.mak b/configs/targets/i386-softmmu.mak index 2ac69d5ba3..2eb0e86250 100644 --- a/configs/targets/i386-softmmu.mak +++ b/configs/targets/i386-softmmu.mak @@ -1,4 +1,5 @@ TARGET_ARCH=i386 TARGET_SUPPORTS_MTTCG=y TARGET_KVM_HAVE_GUEST_DEBUG=y +TARGET_KVM_HAVE_RESET_PARKED_VCPU=y TARGET_XML_FILES= gdb-xml/i386-32bit.xml diff --git a/configs/targets/x86_64-softmmu.mak b/configs/targets/x86_64-softmmu.mak index e12ac3dc59..920e9a4200 100644 --- a/configs/targets/x86_64-softmmu.mak +++ b/configs/targets/x86_64-softmmu.mak @@ -2,4 +2,5 @@ TARGET_ARCH=x86_64 TARGET_BASE_ARCH=i386 TARGET_SUPPORTS_MTTCG=y TARGET_KVM_HAVE_GUEST_DEBUG=y +TARGET_KVM_HAVE_RESET_PARKED_VCPU=y TARGET_XML_FILES= gdb-xml/i386-64bit.xml diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h index c3a60b2890..ab17c09a55 100644 --- a/include/sysemu/kvm.h +++ b/include/sysemu/kvm.h @@ -377,6 +377,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s); int kvm_arch_init_vcpu(CPUState *cpu); int kvm_arch_destroy_vcpu(CPUState *cpu); +#ifdef TARGET_KVM_HAVE_RESET_PARKED_VCPU +void kvm_arch_reset_parked_vcpu(unsigned long vcpu_id, int kvm_fd); +#else +static inline void kvm_arch_reset_parked_vcpu(unsigned long vcpu_id, int kvm_fd) +{ +} +#endif + bool kvm_vcpu_id_is_valid(int vcpu_id); /* Returns VCPU ID to be used on KVM_CREATE_VCPU ioctl() */ diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 8e17942c3b..2ff618fbf1 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -2415,6 +2415,21 @@ void kvm_arch_after_reset_vcpu(X86CPU *cpu) } } +void kvm_arch_reset_parked_vcpu(unsigned long vcpu_id, int kvm_fd) +{ + g_autofree struct kvm_msrs *msrs = NULL; + + msrs = g_malloc0(sizeof(*msrs) + sizeof(msrs->entries[0])); + msrs->entries[0].index = MSR_IA32_TSC; + msrs->entries[0].data = 1; /* match the value in x86_cpu_reset() */ + msrs->nmsrs++; + + if (ioctl(kvm_fd, KVM_SET_MSRS, msrs) != 1) { + warn_report("parked vCPU %lu TSC reset failed: %d", + vcpu_id, errno); + } +} + void kvm_arch_do_init_vcpu(X86CPU *cpu) { CPUX86State *env = &cpu->env;