From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9BA87C46467 for ; Mon, 16 Jan 2023 16:15:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232883AbjAPQPF (ORCPT ); Mon, 16 Jan 2023 11:15:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232891AbjAPQOk (ORCPT ); Mon, 16 Jan 2023 11:14:40 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5639A1CAC1 for ; Mon, 16 Jan 2023 08:08:42 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 106C6B8107A for ; Mon, 16 Jan 2023 16:08:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67160C433D2; Mon, 16 Jan 2023 16:08:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673885319; bh=+0CqO0b06TengcFvuL6jea2IgCjILIpQ8IDa2MHHT2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i5wMGIxeXYnCZjNzsebVa8fGoCKqUzHGuc3LP1/dYZ0gWj7x6I/yclg2gpPshPIS2 9z7tg2b3PnErtUaprirdluusckaWKLYa3VNP1+xc05I1nZ7W/8058uZt/uCwUwVDgy tcNtiW3HFYtMNM3TZP5Fzw5tmjRZ5hcUCJ4RcMq4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Paolo Bonzini , Sasha Levin Subject: [PATCH 5.10 54/64] KVM: x86: Do not return host topology information from KVM_GET_SUPPORTED_CPUID Date: Mon, 16 Jan 2023 16:52:01 +0100 Message-Id: <20230116154745.431127682@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154743.577276578@linuxfoundation.org> References: <20230116154743.577276578@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Paolo Bonzini [ Upstream commit 45e966fcca03ecdcccac7cb236e16eea38cc18af ] Passing the host topology to the guest is almost certainly wrong and will confuse the scheduler. In addition, several fields of these CPUID leaves vary on each processor; it is simply impossible to return the right values from KVM_GET_SUPPORTED_CPUID in such a way that they can be passed to KVM_SET_CPUID2. The values that will most likely prevent confusion are all zeroes. Userspace will have to override it anyway if it wishes to present a specific topology to the guest. Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- Documentation/virt/kvm/api.rst | 14 ++++++++++++++ arch/x86/kvm/cpuid.c | 32 ++++++++++++++++---------------- 2 files changed, 30 insertions(+), 16 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index d807994360d4..2b4b64797191 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6433,6 +6433,20 @@ CPU[EAX=1]:ECX[24] (TSC_DEADLINE) is not reported by ``KVM_GET_SUPPORTED_CPUID`` It can be enabled if ``KVM_CAP_TSC_DEADLINE_TIMER`` is present and the kernel has enabled in-kernel emulation of the local APIC. +CPU topology +~~~~~~~~~~~~ + +Several CPUID values include topology information for the host CPU: +0x0b and 0x1f for Intel systems, 0x8000001e for AMD systems. Different +versions of KVM return different values for this information and userspace +should not rely on it. Currently they return all zeroes. + +If userspace wishes to set up a guest topology, it should be careful that +the values of these three leaves differ for each CPU. In particular, +the APIC ID is found in EDX for all subleaves of 0x0b and 0x1f, and in EAX +for 0x8000001e; the latter also encodes the core id and node id in bits +7:0 of EBX and ECX respectively. + Obsolete ioctls and capabilities ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 06a776fdb90c..de4b171cb76b 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -511,16 +511,22 @@ struct kvm_cpuid_array { int nent; }; +static struct kvm_cpuid_entry2 *get_next_cpuid(struct kvm_cpuid_array *array) +{ + if (array->nent >= array->maxnent) + return NULL; + + return &array->entries[array->nent++]; +} + static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array, u32 function, u32 index) { - struct kvm_cpuid_entry2 *entry; + struct kvm_cpuid_entry2 *entry = get_next_cpuid(array); - if (array->nent >= array->maxnent) + if (!entry) return NULL; - entry = &array->entries[array->nent++]; - entry->function = function; entry->index = index; entry->flags = 0; @@ -698,22 +704,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) entry->edx = edx.full; break; } - /* - * Per Intel's SDM, the 0x1f is a superset of 0xb, - * thus they can be handled by common code. - */ case 0x1f: case 0xb: /* - * Populate entries until the level type (ECX[15:8]) of the - * previous entry is zero. Note, CPUID EAX.{0x1f,0xb}.0 is - * the starting entry, filled by the primary do_host_cpuid(). + * No topology; a valid topology is indicated by the presence + * of subleaf 1. */ - for (i = 1; entry->ecx & 0xff00; ++i) { - entry = do_host_cpuid(array, function, i); - if (!entry) - goto out; - } + entry->eax = entry->ebx = entry->ecx = 0; break; case 0xd: entry->eax &= supported_xcr0; @@ -866,6 +863,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) entry->ebx = entry->ecx = entry->edx = 0; break; case 0x8000001e: + /* Do not return host topology information. */ + entry->eax = entry->ebx = entry->ecx = 0; + entry->edx = 0; /* reserved */ break; /* Support memory encryption cpuid if host supports it */ case 0x8000001F: -- 2.35.1