From nobody Thu Apr 9 12:08:46 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=1773228981; cv=none; d=zohomail.com; s=zohoarc; b=lZN27pze3qS2p7cN3QF8wFWQUr9dhUvxVuvse3Ncb7hbkDfqjTNfG4jGpOw8YQrt9zzePW9socnSu03/P4wzjO6BZycB7BcbwwenvWJjoFBPwHa5Fc6aWP4yoTMA/8WnPyHaOHdVnvddf8ju7yNK4PUKFQAZAAh7DAoOgTQAWHo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1773228981; 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=N5ZBicZO4ATJraH5IwOK76osUl0f+i5tz5Iv6Uq39+o=; b=Z1oLngYuYJYdO4hwCsC7t6fwG7ZwnBgrSfvoRW1cbDO5YlIAZdXopQErXLU0GVgblELHfA+mSZAqJm44unvsYypA5L81dEKVehm6jhs1N7wNw2dEPCV2VAqZf8v5OnukD1sWA/1Dk4kj+V4NyJK2TuKUGsKHdOm1qAF8q6t3Dc0= 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 1773228981723528.1254772082093; Wed, 11 Mar 2026 04:36:21 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w0Hqj-0006jx-UX; Wed, 11 Mar 2026 07:35:37 -0400 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 1w0Hqi-0006jI-7E for qemu-devel@nongnu.org; Wed, 11 Mar 2026 07:35:36 -0400 Received: from linux.microsoft.com ([13.77.154.182]) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w0Hqg-0006GZ-6x for qemu-devel@nongnu.org; Wed, 11 Mar 2026 07:35:35 -0400 Received: from DESKTOP-TUU1E5L.localdomain (unknown [167.220.208.53]) by linux.microsoft.com (Postfix) with ESMTPSA id A43E620B710C; Wed, 11 Mar 2026 04:35:31 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com A43E620B710C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1773228933; bh=N5ZBicZO4ATJraH5IwOK76osUl0f+i5tz5Iv6Uq39+o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mUG4yOt20G+NMFVA8ClLf+wfzNZNX95LIMOEtdesqei3hzzKqE2jrVGTrkMAaj4Uq 1ACDKsLHRiPK06Ggvi2iEaKV/tmb2vYH1Q2nnKg64CVGVSDeV6SAJl1D8+scQZSMC+ gk7QcPCihtKQQTIwfmLxrXulHvsIxeDEMjeaKjJc= From: Magnus Kulke To: qemu-devel@nongnu.org Cc: Zhao Liu , Magnus Kulke , Paolo Bonzini , Wei Liu , Magnus Kulke , Wei Liu Subject: [PATCH v2 8/9] target/i386/mshv: filter out CET bits in cpuid Date: Wed, 11 Mar 2026 12:35:04 +0100 Message-Id: <20260311113505.1177878-9-magnuskulke@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260311113505.1177878-1-magnuskulke@linux.microsoft.com> References: <20260311113505.1177878-1-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: -9 X-Spam_score: -1.0 X-Spam_bar: - X-Spam_report: (-1.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action 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: 1773228983653158500 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 ee25eb5f6f..2c66a52709 100644 --- a/target/i386/mshv/mshv-cpu.c +++ b/target/i386/mshv/mshv-cpu.c @@ -1663,6 +1663,25 @@ 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