From nobody Sun Apr 12 05:51:26 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=linux.microsoft.com ARC-Seal: i=1; a=rsa-sha256; t=1770826168; cv=none; d=zohomail.com; s=zohoarc; b=ha4qwHgGi3CLrzsKK1Nh2m0dc94xMdx/WoVRZ23o3HE8+cw2PHf/vqlGiwuGCcvxBP+vve5kGQLoh+k8cPzVPlGvIgxeXF98dwPHb1fM+vinZ1ug2lSlwxo5dw8WtLRNC0lYtR2+kI7exKl9kKpcza1fBHzfYo5IXT96cmMP9Mo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1770826168; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=HkpGIAxAdQuzfCrev9KQdB7pHBPey4VgXUf/LiB3/ZA=; b=lai/+f6cRqhwwzkTtsTIVd/sAb9KnGnFW1nAVPJlKtXWcujsezQVVSaRnQOpLVi7nb3RCbhwjfRdPk3AKwiuT2WZB87Qp9KmC5CeHXTY45lFAiwioMC3PNZZAyJyZGxzz5JMsmkrNBLOBexymQb6Zr9ka/FT+sHDDm6Bis56Frw= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1770826168618734.7431007589938; Wed, 11 Feb 2026 08:09:28 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vqCkf-0002pn-9g; Wed, 11 Feb 2026 11:07:41 -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 1vqCY5-0007NC-9u for qemu-devel@nongnu.org; Wed, 11 Feb 2026 10:54:41 -0500 Received: from linux.microsoft.com ([13.77.154.182]) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vqCY3-0003Sn-T9 for qemu-devel@nongnu.org; Wed, 11 Feb 2026 10:54:41 -0500 Received: from DESKTOP-TUU1E5L.localdomain (unknown [167.220.208.59]) by linux.microsoft.com (Postfix) with ESMTPSA id 2D83620B7168; Wed, 11 Feb 2026 07:54:37 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 2D83620B7168 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1770825278; bh=HkpGIAxAdQuzfCrev9KQdB7pHBPey4VgXUf/LiB3/ZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZsuVw4evXQXHAL1y1HpNXhZOxfcJ/ECPdYpbsvENzG8IpSt3a3lUTiHPmOlidsi+0 iASIc82W0XwNS48yB1bIevqp5laeUrG+S9+AcnYMNqW4xmEEnPuOw3A0SSKJBr/9wT GZTZfIWfdiG1DO0D76ocKsHgoz4/wGvWMwPBuV1E= From: Magnus Kulke To: qemu-devel@nongnu.org Cc: Magnus Kulke , Wei Liu , Wei Liu , Zhao Liu , Paolo Bonzini , Magnus Kulke Subject: [PATCH 10/10] target/i386/mshv: filter out CET bits in cpuid Date: Wed, 11 Feb 2026 16:54:10 +0100 Message-Id: <20260211155410.203883-11-magnuskulke@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260211155410.203883-1-magnuskulke@linux.microsoft.com> References: <20260211155410.203883-1-magnuskulke@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=13.77.154.182; envelope-from=magnuskulke@linux.microsoft.com; helo=linux.microsoft.com X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Wed, 11 Feb 2026 11:07:32 -0500 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linux.microsoft.com) X-ZM-MESSAGEID: 1770826169948158500 Content-Type: text/plain; charset="utf-8" e46dcef1d0 introduced CET_U/CET_S xstate bits in the ExtSaveArea. The response in EBX of a 0x4,1 cpuid query will contain a size contingent on what the guest enabled in the IA32_XSS MSR (compacted xsave size). Since the MSHV accelerator currently responds with static answers to 0x4d cpuid queries, we'll have to disable those bits, even if the host supports them. Signed-off-by: Magnus Kulke --- target/i386/mshv/mshv-cpu.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/target/i386/mshv/mshv-cpu.c b/target/i386/mshv/mshv-cpu.c index 3a7d9237cd..4d64c54bc6 100644 --- a/target/i386/mshv/mshv-cpu.c +++ b/target/i386/mshv/mshv-cpu.c @@ -1781,6 +1781,25 @@ uint32_t mshv_get_supported_cpuid(uint32_t func, uin= t32_t idx, int reg) if (func =3D=3D 0x01 && reg =3D=3D R_ECX) { ret &=3D ~CPUID_EXT_VMX; } + + /* + * MSHV currently uses static CPUID intercept results for leaf 0xD. + * However there are feature-responses that are dynamic based on what a + * guest enables in XCR0 and XSS, such as CET shadow stack. + * + * A guest which doesn't know about those features yet would encounter= an + * unexpcted CPUID[0xD,1].EBX (compactes XSAVE size) and either fail + * or gracefully degrade by not using XSAVE at all. + * + * To avoid this, we filter out supervisor xstate features. + */ + if (func =3D=3D 0x07 && idx =3D=3D 0 && reg =3D=3D R_ECX) { + ret &=3D ~CPUID_7_0_ECX_CET_SHSTK; + } + if (func =3D=3D 0x07 && idx =3D=3D 0 && reg =3D=3D R_EDX) { + ret &=3D ~CPUID_7_0_EDX_CET_IBT; + } + return ret; } =20 --=20 2.34.1