From nobody Sat Apr 11 07:07:33 2026 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 70C2DC6FA8E for ; Thu, 2 Mar 2023 05:53:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230049AbjCBFxA (ORCPT ); Thu, 2 Mar 2023 00:53:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230098AbjCBFwW (ORCPT ); Thu, 2 Mar 2023 00:52:22 -0500 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8F64532AE; Wed, 1 Mar 2023 21:51:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1677736285; x=1709272285; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=JCKu4lASdy4fofKGHW4gy5ePwfNi7YQxHJ13+kwlv3k=; b=ka5ay/5TeN2UCtOgI6Y2fZeGibJS4uC1tORRFgivbbhHh3rTbb9+VdQH LkceHnsNJhODN6WvYOVhAkzgUPZVnQZfF119eMr55J7dJokQS7jotg4nN 8uebwA21T/7Q7T1bxfKjmbY3Bmk/Pbd6xblY5zzYikdqVtzCwLM1YO3nJ jz7qazwr3AxK8b83OIjNQUB13HW+HuvKZX1JPZ1gsJovv5LhNP7H+tP/Z auMVvLqm5ZYC2HZslxQM9K6qUw0s+UXnnbb8+GP+13bCOluSoDmgiSL07 88neN2qZzArMxT0KmTN28w+9fPABmaL8ZFN5uBcChuWcoa4yANAuGVad6 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10636"; a="420887283" X-IronPort-AV: E=Sophos;i="5.98,226,1673942400"; d="scan'208";a="420887283" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Mar 2023 21:50:52 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10636"; a="920530956" X-IronPort-AV: E=Sophos;i="5.98,226,1673942400"; d="scan'208";a="920530956" Received: from unknown (HELO fred..) ([172.25.112.68]) by fmsmga006.fm.intel.com with ESMTP; 01 Mar 2023 21:50:50 -0800 From: Xin Li To: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, andrew.cooper3@citrix.com, seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com Subject: [PATCH v4 25/34] x86/fred: disallow the swapgs instruction when FRED is enabled Date: Wed, 1 Mar 2023 21:25:02 -0800 Message-Id: <20230302052511.1918-26-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230302052511.1918-1-xin3.li@intel.com> References: <20230302052511.1918-1-xin3.li@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: "H. Peter Anvin (Intel)" The FRED architecture establishes the full supervisor/user through: 1) FRED event delivery swaps the value of the GS base address and that of the IA32_KERNEL_GS_BASE MSR. 2) ERETU swaps the value of the GS base address and that of the IA32_KERNEL_GS_BASE MSR. Thus, the swapgs instruction is disallowed when FRED is enabled, otherwise it cauess #UD. Signed-off-by: H. Peter Anvin (Intel) Tested-by: Shan Kang Signed-off-by: Xin Li --- arch/x86/kernel/process_64.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 57de166dc61c..ff6594dbea4a 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -165,7 +165,8 @@ static noinstr unsigned long __rdgsbase_inactive(void) =20 lockdep_assert_irqs_disabled(); =20 - if (!cpu_feature_enabled(X86_FEATURE_XENPV)) { + if (!cpu_feature_enabled(X86_FEATURE_FRED) && + !cpu_feature_enabled(X86_FEATURE_XENPV)) { native_swapgs(); gsbase =3D rdgsbase(); native_swapgs(); @@ -190,7 +191,8 @@ static noinstr void __wrgsbase_inactive(unsigned long g= sbase) { lockdep_assert_irqs_disabled(); =20 - if (!cpu_feature_enabled(X86_FEATURE_XENPV)) { + if (!cpu_feature_enabled(X86_FEATURE_FRED) && + !cpu_feature_enabled(X86_FEATURE_XENPV)) { native_swapgs(); wrgsbase(gsbase); native_swapgs(); --=20 2.34.1