From nobody Fri Dec 19 03:47:05 2025 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 BF158C77B6E for ; Thu, 13 Apr 2023 17:59:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229927AbjDMR7N (ORCPT ); Thu, 13 Apr 2023 13:59:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40048 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229728AbjDMR7L (ORCPT ); Thu, 13 Apr 2023 13:59:11 -0400 Received: from smtp-fw-9103.amazon.com (smtp-fw-9103.amazon.com [207.171.188.200]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0ACF8A5F; Thu, 13 Apr 2023 10:59:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1681408750; x=1712944750; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=7NPGHZe7ksBAVtMO40tlkfmxNY/cTdX4an+XZxwARlU=; b=DzFFJusJYtIeSq9/CDD+Z7MfSrVKqdm5q7N753NLLe/0RwWAC/EUfwIA a6MkgQWCk9y+sOmUA7m2VCus53vuhomP2BE06kPtXZ78jRy6oxr9bKk6C kgRZrvGueFtwX2XbBzjFmhJLuIT6D/WHoy90Abq3tKE/gdtVCNmA5fXbb U=; X-IronPort-AV: E=Sophos;i="5.99,194,1677542400"; d="scan'208";a="1122409867" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO email-inbound-relay-pdx-2b-m6i4x-cadc3fbd.us-west-2.amazon.com) ([10.25.36.214]) by smtp-border-fw-9103.sea19.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Apr 2023 17:59:01 +0000 Received: from EX19MTAUWC001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan2.pdx.amazon.com [10.236.137.194]) by email-inbound-relay-pdx-2b-m6i4x-cadc3fbd.us-west-2.amazon.com (Postfix) with ESMTPS id 77999A0F1C; Thu, 13 Apr 2023 17:59:01 +0000 (UTC) Received: from EX19D002ANA003.ant.amazon.com (10.37.240.141) by EX19MTAUWC001.ant.amazon.com (10.250.64.174) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.25; Thu, 13 Apr 2023 17:59:01 +0000 Received: from b0f1d8753182.ant.amazon.com (10.95.156.18) by EX19D002ANA003.ant.amazon.com (10.37.240.141) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Thu, 13 Apr 2023 17:58:57 +0000 From: Takahiro Itazuri To: CC: Sean Christopherson , Paolo Bonzini , , Takahiro Itazuri , Takahiro Itazuri Subject: [PATCH v2] KVM: x86: Update KVM_GET_CPUID2 to return valid entry count Date: Thu, 13 Apr 2023 18:58:44 +0100 Message-ID: <20230413175844.21760-1-itazur@amazon.com> X-Mailer: git-send-email 2.38.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.95.156.18] X-ClientProxiedBy: EX19D041UWB003.ant.amazon.com (10.13.139.176) To EX19D002ANA003.ant.amazon.com (10.37.240.141) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Modify the KVM_GET_CPUID2 API to return the number of valid entries in nent field of kvm_cpuid2 even on success. Previously, the KVM_GET_CPUID2 API only updated the nent field when an error was returned. If the API was called with an entry count larger than necessary (e.g., KVM_MAX_CPUID_ENTRIES), it would succeed, but the nent field would continue to show a value larger than the actual number of entries filled by the KVM_GET_CPUID2 API. With this change, users can rely on the updated nent field and there is no need to traverse unnecessary entries and check whether an entry is valid or not. Suggested-by: Sean Christopherson Signed-off-by: Takahiro Itazuri --- Changes v1 -> v2 * Capitalize "kvm" in the commit title. * Remove a scratch "nent" variable. * Link to v1: https://lore.kernel.org/all/20230410141820.57328-1-itazur@ama= zon.com/ arch/x86/kvm/cpuid.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 599aebec2d52..20d28ebdc672 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -523,18 +523,18 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, struct kvm_cpuid_entry2 __user *entries) { - int r; + int r =3D 0; =20 - r =3D -E2BIG; if (cpuid->nent < vcpu->arch.cpuid_nent) - goto out; - r =3D -EFAULT; - if (copy_to_user(entries, vcpu->arch.cpuid_entries, + r =3D -E2BIG; + else if (copy_to_user(entries, vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2))) - goto out; - return 0; + r =3D -EFAULT; =20 -out: + /* + * Update "nent" even on failure, e.g. so that userspace can fix an + * -E2BIG issue by allocating a larger array. + */ cpuid->nent =3D vcpu->arch.cpuid_nent; return r; } --=20 2.39.2