From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D1DF833B6FC; Mon, 20 Apr 2026 15:44:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776699844; cv=none; b=Q4ST6puM2FUTNsqSnDolX9eI4HgN6L0Wm9Uc0rJVMrNf1xMjim1oDih63HpzkCv9fSl/kIZpr0d20tOJdZeU9LIvwU3eVqDLMX5NXDjcvpuqpN/szYoTk6MWALB45ZBHFsXjCGM+LMx6F6abXZUnngNEFc3GdGX0jL4SBNgClMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776699844; c=relaxed/simple; bh=jLCs7Jkv1A1epTMqBUAGPEXP+2MJwIlcZGehOXBYUo0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IxU8zQ9fOYvxb9/sVRarApJYaLDyt29nnkrHVaDxkTOVo+E7irtFUt3DHxMR1t+n2Mb8nf5pCeJOkO41TAXFfqYEapvRVuKTqdpO5F7n8bY1aAqePCil0tr3El9BMRN7U3cQ9d8TvGSf/XhY98S5xybMMOC9MKItP1L6+LWLGJg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VgOHq1Y+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VgOHq1Y+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FD72C19425; Mon, 20 Apr 2026 15:44:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776699844; bh=jLCs7Jkv1A1epTMqBUAGPEXP+2MJwIlcZGehOXBYUo0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VgOHq1Y+w51y3LqgYeuZTRPttA857ESHu2VadFGUL6klFLXKZKQz1wHTTcu49fwgX 1ULgQ0iEKBD5T4N1skPOqsvZ7o75E5ffqLOepGJssma7EGqkIC+KXbVT04GqqIm1I5 8u46VbVVc3nHRHseD7CGfR3Ko5bKD+eT5nJpX3TQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Borislav Petkov (AMD)" , Linus Torvalds Subject: [PATCH 7.0 02/76] x86/CPU: Fix FPDSS on Zen1 Date: Mon, 20 Apr 2026 17:41:13 +0200 Message-ID: <20260420153910.903780184@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260420153910.810034134@linuxfoundation.org> References: <20260420153910.810034134@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Borislav Petkov (AMD) commit e55d98e7756135f32150b9b8f75d580d0d4b2dd3 upstream. Zen1's hardware divider can leave, under certain circumstances, partial results from previous operations. Those results can be leaked by another, attacker thread. Fix that with a chicken bit. Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/msr-index.h | 3 +++ arch/x86/kernel/cpu/amd.c | 3 +++ 2 files changed, 6 insertions(+) --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -674,6 +674,9 @@ #define MSR_AMD64_DC_CFG 0xc0011022 #define MSR_AMD64_TW_CFG 0xc0011023 +#define MSR_AMD64_FP_CFG 0xc0011028 +#define MSR_AMD64_FP_CFG_ZEN1_DENORM_FIX_BIT 9 + #define MSR_AMD64_DE_CFG 0xc0011029 #define MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT 1 #define MSR_AMD64_DE_CFG_LFENCE_SERIALIZE BIT_ULL(MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT) --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -943,6 +943,9 @@ static void init_amd_zen1(struct cpuinfo msr_clear_bit(MSR_K7_HWCR, MSR_K7_HWCR_IRPERF_EN_BIT); clear_cpu_cap(c, X86_FEATURE_IRPERF); } + + pr_notice_once("AMD Zen1 FPDSS bug detected, enabling mitigation.\n"); + msr_set_bit(MSR_AMD64_FP_CFG, MSR_AMD64_FP_CFG_ZEN1_DENORM_FIX_BIT); } static const struct x86_cpu_id amd_zenbleed_microcode[] = {