From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (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 76D853009DA; Fri, 7 Nov 2025 19:55:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762545344; cv=none; b=DcxTeULJAa/lybIHQ+Vw6nB7vXB6davqaPmh7cCkQs8KT0V4E0aqDJ+U8oiTR5Vnsi4Rk77TG2+Od9LtMHbDrQKpj31bMywtc4W0lYhDh+6vvDBN3xRpKs1Djev7HLRiVHwYjYVPyk8nfq70sAiLgBYKWI7zQgRXwW5B7hzyd4s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762545344; c=relaxed/simple; bh=M90qio2q2Tipd7ZAbCDj4FfpWg8WnNV9xphFskIDfMs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=SLEP2uDZgO/UPyXEb10AUiXd0+nbpfTnuY5PROkoifrNkKeCpVSUbKWUpXlu9NqJBcvzDGldWKorN7PjI72TP+HK/xTg3P8tmg1Cbl0MsaDkkUGUNZOJEiqUV4g5gLxQ14BZco8Rl9VnXEXgsC8tQcSHz05YSLXZA1lz5Y7RvxA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=aijEOupB; arc=none smtp.client-ip=192.198.163.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="aijEOupB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1762545343; x=1794081343; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=M90qio2q2Tipd7ZAbCDj4FfpWg8WnNV9xphFskIDfMs=; b=aijEOupB67CuPJldSrctNpUmfrMCn4mrDfk6ZddxdkmiOACYeM5E6m62 DhxhQokmQS+jQYt1xITqC89OQBhK+jPxr2WgJQl2qp07C5lmBG2wsE22q tX2aa7kJNMXvprWFBBKODDLHuHwgxnCnU+m3/9w7RD0ajJcZsRO+sxBxO e5Exu5C8y1+8n6owTlanLxFhPHE1WqYPAz+5klpeESyl8+ifOSHB/sOwC DAzys0HeIjL4GYYQATM8bv+Id5BeEInz8UkwvV+aWRCZMA9h8gxUT0aY/ tptsMErZLCTaIOAM0EMa/nog3Ro+zenBomaM7epVyeLgJ44M8zCYdIkOl g==; X-CSE-ConnectionGUID: DkF8t37qSW6CC5uampQY6A== X-CSE-MsgGUID: ReJcGrNeRIa1sPGjn6Vwtg== X-IronPort-AV: E=McAfee;i="6800,10657,11606"; a="75391013" X-IronPort-AV: E=Sophos;i="6.19,287,1754982000"; d="p7s'346?scan'346,208,346";a="75391013" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Nov 2025 11:55:42 -0800 X-CSE-ConnectionGUID: lCRAJXZfQL2Pb1l3lbn3Aw== X-CSE-MsgGUID: tJd97CxMQrilUqTvy2THQw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,287,1754982000"; d="p7s'346?scan'346,208,346";a="187370495" Received: from tjmaciei-mobl5.jf.intel.com (HELO tjmaciei-mobl5.localnet) ([10.24.81.83]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Nov 2025 11:55:42 -0800 From: Thiago Macieira To: "Jason A. Donenfeld" Cc: Borislav Petkov , Christopher Snowhill , Gregory Price , x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, mario.limonciello@amd.com, riel@surriel.com, yazen.ghannam@amd.com, me@mixaill.net, kai.huang@intel.com, sandipan.das@amd.com, darwi@linutronix.de, stable@vger.kernel.org Subject: Re: [PATCH v2] x86/amd: Disable RDSEED on AMD Zen5 because of an error. Date: Fri, 07 Nov 2025 11:55:35 -0800 Message-ID: <2790505.9o76ZdvQCi@tjmaciei-mobl5> Organization: Intel Corporation In-Reply-To: References: <1903914.sHLxoZxqIA@tjmaciei-mobl5> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart3363618.vuYhMxLoTh"; micalg="sha256"; protocol="application/pkcs7-signature" --nextPart3363618.vuYhMxLoTh Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" On Friday, 7 November 2025 11:13:28 Pacific Standard Time Jason A. Donenfeld wrote: > > But consider people who haven't upgraded Linux (yes, we get people asking > > to keep everything intact in their system, but upgrade Qt only, then > > complain when our dependency minimums change). How much of an impact > > would they have? > I suppose you could benchmark it and see if it matters. The syscall is > obviously slower than the megafast vDSO code, so it will probably also > be a bit slower than the MT code. But I suspect for most use cases maybe > it doesn't matter that much? It's worth a try and seeing if anybody > complains. I'm not asking about the performance of generating new random numbers in this process. I am asking about the system-wide impact that draining the entropy source would have. Is that a bad thing? I suspect the answer is "no" because it's the same as /dev/urandom anyway. -- Thiago Macieira - thiago.macieira (AT) intel.com Principal Engineer - Intel DCG - Platform & Sys. 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