From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 18F85C624D4 for ; Tue, 1 Sep 2026 14:58:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=56BaSgitaCOqK+plEdyRoTXW75Ul7dUQbsnofeonq2Q=; b=Tjl1HzTmN1I7N5o9kxTN06L3kp jF5ZFXz4YsQLjmj96MW/PbrLuM3l9JnWm46rxdfvFM0NKS3zeYBJ36jgi7UjIhcEc3FiT6mAHN6UV slNlczHSCWtyQgzwFvRy7b3xZ2lgkWnI7wLcYMlADvMA8TfLfFU22XiMYR194HTDp7BpfMrp2zLJq vR7wlz007/Sk5ShNlBDy+vQFV5RGugSN4Wvfz2vlt3ENYISk/V2e0P34/BstqFw2Vg2OJTchNZEeQ TN6LlaF4nlgTaK+F3n4iR6evwW3s+a+WmFRFk+SEysve9NRtwmfvY12jSwRbqW5P+hnRN9TCsVZwA tZ2SUYSA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1PwE-0000000COUM-1Op0; Tue, 01 Sep 2026 14:58:14 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1PwD-0000000COU8-2Hws for linux-um@lists.infradead.org; Tue, 01 Sep 2026 14:58:13 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id EABAA432DA; Tue, 1 Sep 2026 14:58:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 945BD1F00A3A; Tue, 1 Sep 2026 14:58:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788274692; bh=56BaSgitaCOqK+plEdyRoTXW75Ul7dUQbsnofeonq2Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cysZZLRFOedPPPO//ebfnqWoUAq3ACVHOVowkBLYsRGJLs6dfZ4GNpCIgWF8XKMl1 +j2GuQzQOQYK2TfKBNUBNFBBBDAome86zQr8Y51X0jKUXLbqT7cUPA5HtWWPlVeWYp q9mPHrT1s2gFffWPqNKVAgQzr/VaTwoUwNWRsBSMphHqgRR6Nr3HvGEVWWc4XryRgv MPKfD0cf/YATfgKkrTbxcTyyJeOhB37+rZm0meKJhRjmx/HJ7FE+qIGsBHR0i1j4Er woSJpjWbnwlL67kE3yJx7iy9nBBIo5e9Cggk0yhLyETt1PzFjhw+8uWH6XGUw+Nn7d Nd9Xn71cRSTxA== From: Eric Biggers To: x86@kernel.org Cc: linux-um@lists.infradead.org, linux-raid@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , Andrew Morton , Eric Biggers Subject: [PATCH v5 1/8] x86/fpu: Check for missing AVX and AVX-512 xstate bits Date: Tue, 1 Sep 2026 07:57:33 -0700 Message-ID: <20260901145740.42337-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260901145740.42337-1-ebiggers@kernel.org> References: <20260901145740.42337-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org If the CPU declares AVX or AVX-512 support, verify that the corresponding xstate bits are also set. If not, warn and clear them. This eliminates the perceived need for AVX and AVX-512 optimized code in the kernel to call cpu_has_xfeatures(). That has never been universally done, which strongly suggests that it has never really been needed in practice, but this should remove any remaining doubt. Acked-by: Christoph Hellwig Signed-off-by: Eric Biggers --- arch/x86/kernel/fpu/xstate.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index a7b6524a9dea..97cfd4fb6cc0 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -806,7 +806,7 @@ static u64 __init guest_default_mask(void) void __init fpu__init_system_xstate(unsigned int legacy_size) { unsigned int eax, ebx, ecx, edx; - u64 xfeatures; + u64 xfeatures, mask; int err; int i; @@ -818,6 +818,8 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) if (!boot_cpu_has(X86_FEATURE_XSAVE)) { pr_info("x86/fpu: x87 FPU will use %s\n", boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE"); + /* Disable all dependent flags too */ + setup_clear_cpu_cap(X86_FEATURE_XSAVE); return; } @@ -833,7 +835,8 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) cpuid_count(CPUID_LEAF_XSTATE, 1, &eax, &ebx, &ecx, &edx); fpu_kernel_cfg.max_features |= ecx + ((u64)edx << 32); - if ((fpu_kernel_cfg.max_features & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { + mask = XFEATURE_MASK_FPSSE; + if ((fpu_kernel_cfg.max_features & mask) != mask) { /* * This indicates that something really unexpected happened * with the enumeration. Disable XSAVE and try to continue @@ -844,6 +847,24 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) goto out_disable; } + mask |= XFEATURE_MASK_YMM; + if (boot_cpu_has(X86_FEATURE_AVX)) { + if ((fpu_kernel_cfg.max_features & mask) != mask) { + pr_err(FW_BUG + "x86/fpu: Disabling AVX support due to missing xstate features\n"); + setup_clear_cpu_cap(X86_FEATURE_AVX); + } + } + + mask |= XFEATURE_MASK_AVX512; + if (boot_cpu_has(X86_FEATURE_AVX512F)) { + if ((fpu_kernel_cfg.max_features & mask) != mask) { + pr_err(FW_BUG + "x86/fpu: Disabling AVX-512 support due to missing xstate features\n"); + setup_clear_cpu_cap(X86_FEATURE_AVX512F); + } + } + if (fpu_kernel_cfg.max_features & XFEATURE_MASK_APX && fpu_kernel_cfg.max_features & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)) { /* -- 2.55.0