From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from SN4PR0501CU005.outbound.protection.outlook.com (mail-southcentralusazon11011036.outbound.protection.outlook.com [40.93.194.36]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 41E2F35F165 for ; Mon, 13 Jul 2026 06:28:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.93.194.36 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783924139; cv=fail; b=b9O4sFOa5cFTXn5rqVmFpSEUUZTWGvC6FJ+orkFbMvjtYLvNx81zq5dafpSvbKCnaOqqWnwrDqMXWs5AGRxhnHFVeyyGy1cgJBTwlQBb70Ba6jgGcbdk/UAYtExkibUYzD7Q1+5qV11Y897cMcKciIRWT+2xdYTzehgzm03iGV0= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783924139; c=relaxed/simple; bh=k2QeE2mtOsgWPNXddiOFRm4Rguj5gg7NKVuSWEUkRS8=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=X/SKHJzQwrfkBJ6ow7qJpH7HLWLWK1Uq7q+MM5ICieaj3NmfmNPKlOJ+GRUcAXtwoJg7kGgPoiL56eW/AOUHMO98i+Rul96EYQP1cLrC6JNJ5Ag5UseqsZgd9yPOQ+Jo6wMHGvDrNikuB3UZiRCrhjid29VAC6B8lIbKc34TIBU= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=W2mdjwZe; arc=fail smtp.client-ip=40.93.194.36 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="W2mdjwZe" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=kD7DAp3LLmZYtLGALo+N4TIdusCQPL/6zx/iTnV0SenUoiblkgEfdmS1btOGbBCDRbJ+MVjHnEL14ipqi6uebMC3ee4STQZ1j7chfprMvE0KCzDP+MyQRJIbb4+OQ64ChFfd5WiZgZGPJiJblEyl568CoWKAaFNGZSX0QEzMC091zzTeQUXMzTKuqy87uct4SLD+qAd2Je39IGZ4cmlpKUY1KPX+tfUrASZYLgQmqhTmJ54Ps9ELRCAnfd+DXoFMhU0R0Gl6vdhJHHpKOgDQr0VJHiuHiUxmBniMEhgF+fqzw7GN2USwB6X4j/Yt/rTgF0TAQcAUDaioEhjIJTIpdg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=R7mLbIy1MZV6uHlI8av2dc0YprLPNkZt9SCpaWftgeA=; b=HTM/XzpbrrRRacPsVzJJki7Rmmw40ErekO6oI+I4k9t0m2tzczMpCFVxIWm5jNJMKiZbwkPfpgRicCI6UitoQb1GD3hpSgKzUU5iQsMU/f81XJTzA2GteHbH6jqOVYrBJDj0XkvZt9tFqzr50/3HVdN+0xfWMubCo+1IpQKguGoNiiJh7d5tndHt002h/ExMbdjS75qO2fXj1DIPeEla6nd/ctXkLNK5W61FaTlq4z6iuM4oSMkEsDujyZQevbOVEuUOM8bW6Cwl/fA9aEsRey1hswCF5mZIRwMOVM9+EeAn8fg15tqVVldGpl3VjH2TkInJWhMeTJKe3hAwiz991Q== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 165.204.84.17) smtp.rcpttodomain=kernel.org smtp.mailfrom=amd.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=amd.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=R7mLbIy1MZV6uHlI8av2dc0YprLPNkZt9SCpaWftgeA=; b=W2mdjwZe6+SOv29YFbm2IFil0EQ5LtnFjbqjLBYye70Df7ErsPNllzAvT9hY7VYmkLMPMrptu5MpAK6XX8weRpgTYBXRjRhiEu4S0J8BTGZFaDTvcQTEQCQKm0JwNY02mVjCBoDWxwOC0rss8mK6eIZDRrG9hxMsPSYaJf34aRE= Received: from BY1P220CA0040.NAMP220.PROD.OUTLOOK.COM (2603:10b6:a03:59e::16) by SJ2PR12MB8063.namprd12.prod.outlook.com (2603:10b6:a03:4d1::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.202.18; Mon, 13 Jul 2026 06:28:51 +0000 Received: from SJ5PEPF000001CB.namprd05.prod.outlook.com (2603:10b6:a03:59e:cafe::62) by BY1P220CA0040.outlook.office365.com (2603:10b6:a03:59e::16) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.21.202.19 via Frontend Transport; Mon, 13 Jul 2026 06:28:51 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by SJ5PEPF000001CB.mail.protection.outlook.com (10.167.242.40) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.223.9 via Frontend Transport; Mon, 13 Jul 2026 06:28:51 +0000 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.41; Mon, 13 Jul 2026 01:28:51 -0500 Received: from [10.136.45.190] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.41 via Frontend Transport; Mon, 13 Jul 2026 01:28:47 -0500 Message-ID: <175172b6-94d1-4552-a477-e07c202de3bb@amd.com> Date: Mon, 13 Jul 2026 11:58:41 +0530 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/5] KVM: nSVM: Disable LBRV in nested control cache when unsupported To: Yosry Ahmed CC: , , , , , , , , , , , , Shivansh Dhiman References: <20260709082953.69434-1-shivansh.dhiman@amd.com> <20260709082953.69434-3-shivansh.dhiman@amd.com> Content-Language: en-US From: Shivansh Dhiman In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ5PEPF000001CB:EE_|SJ2PR12MB8063:EE_ X-MS-Office365-Filtering-Correlation-Id: 153e87bc-b248-4cff-815c-08dee0a80154 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|23010399003|376014|36860700016|22082099003|18002099003|4143699003|56012099006|11063799006; X-Microsoft-Antispam-Message-Info: GuiBQjaKIfH5DpT/J+kxecqSIhtz5gZo/VHtWrKOKf0hFdKGk5u/4Vi0rhjuJoLdOovJD8p/oa3pfW8HhJ0V6DhrSjYO6i5b4/HlAl2edToQq3bZi4V+axCMDj02ZLQ+eaBM8s2H/RwY2IVJO1GwWPVWcVM+UPU9sPBdm7HeW0SfguneWGv9flNjo6KF49OKwBsTGbcwPPyA3COD3z4iTqEGZO7tP1wOZDDF6a9pn522eEeLOpfMmThQZXFDyux7qCJdthv2p1FGxk02ydNU59R3P3/xGHOC/Q2IzqEljZHb4RyZGLw6EoCqWYR4B/D/MPqoV+9TzINEru3n5NEMZdMJ2jXRHm9SHw/Rnf/ZK93BQaF5DW4fvaDBytz/GbFSdg3UXhoeHzGhqn3jgdcT3P6jAGe1EGUHJdUR+K3Z6hIpqQefSJ3rtXT7Tw26WRrU670lJTSTVFf7zouoaaf6r8MYudlvz8UrOkgLnh4UOIGmF7Xp+KdjDFm5hND3nxfcOWmvNOQWh1OG5pxStqoLMOJs9RYkLT573ie0wTDzWBCE3A00I8fqf7XspDK50Ls5FgIiX9kv+5sMZXgrnizCgxkHTD9v6rHNBtNJJqGhlGE3BjRv/jlyNWVHrnPlX+JH7AMNhNbR59OSmsQgIZqoM0/SaC0GiZTljmjLulpJW0Fynbmmm3oJuz3hgGEWTvZ7xntdyX6QesPXC21lrVqkzw== X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb08.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(23010399003)(376014)(36860700016)(22082099003)(18002099003)(4143699003)(56012099006)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: NjcV8v1Zf5NIL7wcULN4C7FaSTc6zcnUgajtoBIx3tdm0NbUPstSkDyD0zNX0HJViTetjs7xrB8kc42nz5RwFkACRtqC0nVeGE1cj6gmC5IzkM9R+nr8jnf8vWFSrDMdWlzWp7UZ9mfuDf+FwQgbrASGSjvlE8jONbfSfNIUqBLChPy7hNe4d0lw3AGItz2eGe2zIXjWIO6GabKDYPfLndmPPtWdi8qH2/x8c6BonI612qI0leEyc5muRxcqU2YIYQtKKF5JoLE5zo/E2TVGn38fLL42gnjLXLVP9+V8j8OmNDS7ZWld9hTDxcBK2su9y056lV6JC+eQGStOvlZfy/+xu/dp0Xj71Gjw+cYDkuCacj2rgzfGslLizmsTRTH/JZzl/IVT/NWct8w6vKEg6prQHPumU5dEYe7qh7gzvUbqLEJpOeksqqgkd7+DxIRS X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jul 2026 06:28:51.3988 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 153e87bc-b248-4cff-815c-08dee0a80154 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ5PEPF000001CB.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8063 On 10-07-26 01:18, Yosry Ahmed wrote: > On Thu, Jul 9, 2026 at 1:32 AM Shivansh Dhiman wrote: >> >> Clear SVM_MISC2_ENABLE_V_LBR in __nested_copy_vmcb_control_to_cache() when >> the vCPU does not support LBR Virtualization. This lets the cached value be >> consumed directly instead of re-checking X86_FEATURE_LBRV on every access. >> >> Suggested-by: Yosry Ahmed >> Signed-off-by: Shivansh Dhiman >> --- >> Changelog: >> v3: >> * New patch. >> * Sanitize V_LBR in the cache and drop the redundant X86_FEATURE_LBRV >> checks (Yosry Ahmed). >> >> --- >> arch/x86/kvm/svm/nested.c | 9 ++++++--- >> 1 file changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c >> index d3df6b22bfef..84248e6665cf 100644 >> --- a/arch/x86/kvm/svm/nested.c >> +++ b/arch/x86/kvm/svm/nested.c >> @@ -534,6 +534,11 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu, >> if (!gmet_enabled || !guest_cpu_cap_has(vcpu, X86_FEATURE_GMET)) >> to->misc_ctl &= ~SVM_MISC_ENABLE_GMET; >> >> + /* Always clear misc_ctl2 bits that the guest cannot use */ > > I think the comment here is unnecessary, the comment above for > misc_ctl should already make this clear. [...] > >> + to->misc_ctl2 = from->misc_ctl2; >> + if (!lbrv || !guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV)) > > Do we need to check lbrv here? KVM should not set X86_FEATURE_LBRV if > lbrv=0 anyway, right? Makes sense on both comments. I'll remove the comment and the !lbrv check in next version. > >> + to->misc_ctl2 &= ~SVM_MISC2_ENABLE_V_LBR; >> + >> to->iopm_base_pa = from->iopm_base_pa & PAGE_MASK; >> to->msrpm_base_pa = from->msrpm_base_pa & PAGE_MASK; >> to->tsc_offset = from->tsc_offset;