From nobody Thu Jul 10 07:40:05 2025 Delivered-To: importer2@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer2=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1677679391489890.7319553162558; Wed, 1 Mar 2023 06:03:11 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pXMxD-0000zK-Nt; Wed, 01 Mar 2023 08:57:11 -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 1pXMtA-0000Kp-HF for qemu-devel@nongnu.org; Wed, 01 Mar 2023 08:53:02 -0500 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXMt0-0002rJ-Lv for qemu-devel@nongnu.org; Wed, 01 Mar 2023 08:52:59 -0500 Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pXMsb-00EuVW-2a; Wed, 01 Mar 2023 13:52:39 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1pXMsb-0049Tx-2C; Wed, 01 Mar 2023 13:52:25 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=Zi4EEA2qnGvfBIJWdSw/uhiNLbWMa2NWdi+DKFqz+io=; b=LvnQIvHeL1kLoswnIWH2rTC6x9 NWy6+oZV1JlyoVetVJGfo7+B+JJ2wgbGN9d5FAaPJooH/D/o3Rm/QfuBl7P17CL+ct0BG+38wBHMD GeinDPLJViiqJP8zOllw44azNtiGknkIfuT1OO99yonXZoS1sCja3blvJ2pc33+6pT8e+Z6UfHQ6p CEaAPZv3SOBZLAvgWPJSysZE4ay0Wl7ylaOtY2KCCstEKQ9YqU/e4CB0SdA7me8UXUHbFRfr7EnUZ fbMFIXAS8ThmB0ny+rQQb2TpaXxLOiX5RIqjmHc4EBhYPFuFv61lmgWZc4aFX7DeI5SNrC0dfgmRd RWauBEVg==; From: David Woodhouse To: Peter Maydell , qemu-devel@nongnu.org Cc: Paolo Bonzini , Paul Durrant , Joao Martins , Ankur Arora , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Thomas Huth , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Juan Quintela , "Dr . David Alan Gilbert" , Claudio Fontana , Julien Grall , "Michael S. Tsirkin" , Marcel Apfelbaum , armbru@redhat.com, Stefano Stabellini , vikram.garhwal@amd.com Subject: [PATCH v15 06/60] i386/kvm: Set Xen vCPU ID in KVM Date: Wed, 1 Mar 2023 13:51:29 +0000 Message-Id: <20230301135223.988336-7-dwmw2@infradead.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230301135223.988336-1-dwmw2@infradead.org> References: <20230301135223.988336-1-dwmw2@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer2=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: none client-ip=2001:8b0:10b:1:d65d:64ff:fe57:4e05; envelope-from=BATV+1cb70579e185fe7dd8a8+7129+infradead.org+dwmw2@desiato.srs.infradead.org; helo=desiato.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 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+importer2=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer2=patchew.org@nongnu.org X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1677679393603100001 Content-Type: text/plain; charset="utf-8" From: David Woodhouse There are (at least) three different vCPU ID number spaces. One is the internal KVM vCPU index, based purely on which vCPU was chronologically created in the kernel first. If userspace threads are all spawned and create their KVM vCPUs in essentially random order, then the KVM indices are basically random too. The second number space is the APIC ID space, which is consistent and useful for referencing vCPUs. MSIs will specify the target vCPU using the APIC ID, for example, and the KVM Xen APIs also take an APIC ID from userspace whenever a vCPU needs to be specified (as opposed to just using the appropriate vCPU fd). The third number space is not normally relevant to the kernel, and is the ACPI/MADT/Xen CPU number which corresponds to cs->cpu_index. But Xen timer hypercalls use it, and Xen timer hypercalls *really* want to be accelerated in the kernel rather than handled in userspace, so the kernel needs to be told. Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant --- target/i386/kvm/kvm.c | 5 +++++ target/i386/kvm/xen-emu.c | 28 ++++++++++++++++++++++++++++ target/i386/kvm/xen-emu.h | 1 + 3 files changed, 34 insertions(+) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index aac43174e8..edcf8a2a65 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -1884,6 +1884,11 @@ int kvm_arch_init_vcpu(CPUState *cs) } } =20 + r =3D kvm_xen_init_vcpu(cs); + if (r) { + return r; + } + kvm_base +=3D 0x100; #else /* CONFIG_XEN_EMU */ /* This should never happen as kvm_arch_init() would have died fir= st. */ diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c index 34d5bc1bc9..4883b95d9d 100644 --- a/target/i386/kvm/xen-emu.c +++ b/target/i386/kvm/xen-emu.c @@ -52,6 +52,34 @@ int kvm_xen_init(KVMState *s, uint32_t hypercall_msr) return 0; } =20 +int kvm_xen_init_vcpu(CPUState *cs) +{ + int err; + + /* + * The kernel needs to know the Xen/ACPI vCPU ID because that's + * what the guest uses in hypercalls such as timers. It doesn't + * match the APIC ID which is generally used for talking to the + * kernel about vCPUs. And if vCPU threads race with creating + * their KVM vCPUs out of order, it doesn't necessarily match + * with the kernel's internal vCPU indices either. + */ + if (kvm_xen_has_cap(EVTCHN_SEND)) { + struct kvm_xen_vcpu_attr va =3D { + .type =3D KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID, + .u.vcpu_id =3D cs->cpu_index, + }; + err =3D kvm_vcpu_ioctl(cs, KVM_XEN_VCPU_SET_ATTR, &va); + if (err) { + error_report("kvm: Failed to set Xen vCPU ID attribute: %s", + strerror(-err)); + return err; + } + } + + return 0; +} + uint32_t kvm_xen_get_caps(void) { return kvm_state->xen_caps; diff --git a/target/i386/kvm/xen-emu.h b/target/i386/kvm/xen-emu.h index 2101df0182..d62f1d8ed8 100644 --- a/target/i386/kvm/xen-emu.h +++ b/target/i386/kvm/xen-emu.h @@ -24,5 +24,6 @@ #define XEN_VERSION(maj, min) ((maj) << 16 | (min)) =20 int kvm_xen_init(KVMState *s, uint32_t hypercall_msr); +int kvm_xen_init_vcpu(CPUState *cs); =20 #endif /* QEMU_I386_KVM_XEN_EMU_H */ --=20 2.39.0