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Tue, 28 Oct 2025 08:33:24 -0700 (PDT) Message-ID: Date: Tue, 28 Oct 2025 16:33:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: [PATCH v2 for-4.21 1/2] x86/AMD: disable RDSEED on Fam17 model 47 stepping 0 From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Oleksii Kurochko References: <272093dc-c97c-434a-9977-ad1c26e7e229@suse.com> Content-Language: en-US Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <272093dc-c97c-434a-9977-ad1c26e7e229@suse.com> Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1761665624444154100 Content-Type: text/plain; charset="utf-8" This particular variant has an error that causes RDSEED to always return 0xffffffff, while RDRAND works correctly. Inspired by Linux commit 5b937a1ed64ebeba8876e398110a5790ad77407c ("x86/rdrand: Disable RDSEED on AMD Cyan Skillfish"). Like for RDRAND, permit a command line override to be used to keep RDSEED enabled. Signed-off-by: Jan Beulich --- Considering how it is described, I didn't think probing RDSEED (like we do for RDRAND) would be necessary. Am I going too far in also updating cpuidmask_defaults here, or is us not doing so for the RDRAND disabling actually an oversight? Using warning_add() may not be quite appropriate, as we don't really mean the admin to possibly override this with "cpuid=3Drdseed" (that's only a last resort, in case the issue is yet more limited in scope). But mere printk() would feel like hiding the information in the middle of lots of other output. --- v2: Correctly check model, not (again) family. --- a/xen/arch/x86/cpu/amd.c +++ b/xen/arch/x86/cpu/amd.c @@ -1219,6 +1219,24 @@ static void cf_check init_amd(struct cpu } break; =20 + case 0x17: + /* + * Fam17 model 47 stepping 0 has an error that causes RDSEED to + * always return 0xffffffff (while RDRAND works correctly). + */ + if (c =3D=3D &boot_cpu_data && + c->model =3D=3D 0x47 && c->stepping =3D=3D 0 && + cpu_has(c, X86_FEATURE_RDSEED) && + !is_forced_cpu_cap(X86_FEATURE_RDSEED)) { + static const char __initconst text[] =3D + "RDSEED is unreliable on this hardware; disabling its exposure\n"; + + setup_clear_cpu_cap(X86_FEATURE_RDSEED); + cpuidmask_defaults._7ab0 &=3D ~cpufeat_mask(X86_FEATURE_RDSEED); + warning_add(text); + } + break; + case 0x19: /* * Zen3 (Fam19h model < 0x10) parts are not susceptible to --- a/xen/arch/x86/cpu-policy.c +++ b/xen/arch/x86/cpu-policy.c @@ -123,6 +123,10 @@ static void __init cf_check _parse_xen_c else if ( feat =3D=3D X86_FEATURE_RDRAND && (cpuid_ecx(1) & cpufeat_mask(X86_FEATURE_RDRAND)) ) setup_force_cpu_cap(X86_FEATURE_RDRAND); + else if ( feat =3D=3D X86_FEATURE_RDSEED && + cpuid_eax(0) >=3D 7 && + (cpuid_count_ebx(7, 0) & cpufeat_mask(X86_FEATURE_RDSEED)) ) + setup_force_cpu_cap(X86_FEATURE_RDSEED); } =20 static int __init cf_check parse_xen_cpuid(const char *s) From nobody Thu Oct 30 15:22:14 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=quarantine dis=none) header.from=suse.com ARC-Seal: i=1; a=rsa-sha256; t=1761665659; cv=none; d=zohomail.com; s=zohoarc; b=C8SLf9FM/uuRNLhHOsRZIIk9XIr0gzhKrNPcLqp7pyPg/lhGmaUd9ygghPlIV2K9e8c42GMZJb2pUUOBoGYNCsmuDSq5J9NSWMBIeOj/sxzVAd5UmhrsFAFDGar74Hr5L/Fh/XK/kIPBKUHDbh/4PsWjlp8/HadDLJsagCjcYds= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1761665659; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=OIqrBm27xeex8ooYRBuiIqavGVudqwN/SmgOkYYu3Ts=; b=IiJGmk6uaN4vx/ZPeyYngRWeKdT7LgH/Khuy7BXClLZWIXEA1TCzmQ1KAXMS2UEX+48RJlJkAOq/N9k19qZUnIkDPGpsEUs5VLRu09HTzZFLdBctQxWja2ty67I/o7cZR92daRIgXt/IQGhktSnYUoc+XPsqmhxdpQpVi1ipmPA= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1761665659381484.0441285149493; Tue, 28 Oct 2025 08:34:19 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.1152238.1482752 (Exim 4.92) (envelope-from ) id 1vDli0-0000eJ-DA; Tue, 28 Oct 2025 15:34:04 +0000 Received: by outflank-mailman (output) from mailman id 1152238.1482752; Tue, 28 Oct 2025 15:34:04 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1vDli0-0000eC-9e; Tue, 28 Oct 2025 15:34:04 +0000 Received: by outflank-mailman (input) for mailman id 1152238; Tue, 28 Oct 2025 15:34:03 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1vDlhz-0008I1-1A for xen-devel@lists.xenproject.org; Tue, 28 Oct 2025 15:34:03 +0000 Received: from mail-wr1-x430.google.com (mail-wr1-x430.google.com [2a00:1450:4864:20::430]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 87c019ca-b413-11f0-9d16-b5c5bf9af7f9; Tue, 28 Oct 2025 16:34:02 +0100 (CET) Received: by mail-wr1-x430.google.com with SMTP id ffacd0b85a97d-4298b49f103so2146268f8f.2 for ; Tue, 28 Oct 2025 08:34:02 -0700 (PDT) Received: from [10.156.60.236] (ip-037-024-206-209.um08.pools.vodafone-ip.de. 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Tue, 28 Oct 2025 08:34:01 -0700 (PDT) Message-ID: <954766c0-04e3-4087-a578-cd88ea7e1c40@suse.com> Date: Tue, 28 Oct 2025 16:34:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: [PATCH v2 for-4.21 2/2] x86/AMD: disable RDSEED on most of Zen5 From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Oleksii Kurochko References: <272093dc-c97c-434a-9977-ad1c26e7e229@suse.com> Content-Language: en-US Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <272093dc-c97c-434a-9977-ad1c26e7e229@suse.com> Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1761665662426154101 Content-Type: text/plain; charset="utf-8" This particular variant has an error that causes 16- and 32-bit forms of RDSEED to frequently return 0 while still signaling success (CF=3D1). Refer to AMD-SB-7055 / CVE-2025-62626. Relevant data taken from Linux commit ("x86/CPU/AMD: Add RDSEED fix for Zen5"). As for the other RDSEED issue, the same command line override can be used to keep RDSEED enabled. [1] https://lore.kernel.org/lkml/176165291198.2601451.3074910014537130674.t= ip-bot2@tip-bot2/T/#u Signed-off-by: Jan Beulich --- See "x86/AMD: disable RDSEED on Fam17 model 47 stepping 0" for pending opens. --- v2: New. --- a/xen/arch/x86/cpu/amd.c +++ b/xen/arch/x86/cpu/amd.c @@ -1246,6 +1246,43 @@ static void cf_check init_amd(struct cpu if (!cpu_has_hypervisor && !cpu_has(c, X86_FEATURE_BTC_NO)) __set_bit(X86_FEATURE_BTC_NO, c->x86_capability); break; + + case 0x1a: + /* + * Zen5 have an error that causes the 16- and 32-bit forms of + * RDSEED to frequently return 0 while signaling success (CF=3D1). + * Sadly at the time of writing the fixed microcode revision is + * known for only two of the models. + */ + if (c =3D=3D &boot_cpu_data && + cpu_has(c, X86_FEATURE_RDSEED) && + !is_forced_cpu_cap(X86_FEATURE_RDSEED)) { + static const char __initconst text[] =3D + "RDSEED32 is unreliable on this hardware; disabling its exposure\n"; + bool good =3D false; + + switch (c->model) { + case 0x02: + if (c->stepping =3D=3D 1 && + this_cpu(cpu_sig).rev >=3D 0x0b00215a) + good =3D true; + break; + + case 0x11: + if (c->stepping =3D=3D 0 && + this_cpu(cpu_sig).rev >=3D 0x0b101054) + good =3D true; + break; + } + + if (good) + break; + + setup_clear_cpu_cap(X86_FEATURE_RDSEED); + cpuidmask_defaults._7ab0 &=3D ~cpufeat_mask(X86_FEATURE_RDSEED); + warning_add(text); + } + break; } =20 display_cacheinfo(c);