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 C55843009CB; Fri, 7 Nov 2025 23:07:23 +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=1762556843; cv=none; b=LpgxN2aDY5/H3iJ1Ubm2GTSJa9vcR8sRPEvCo6MW391ykdLxXkhxC88h+H6FnY1i3II4qhu63qFgXqBJPZOhPduCNB57yN28Ck414KUBQPu5p7bBFP05+vqQYTYdWF0JW7xv1XXBHSuC6F5vVhcckAfCSs+LOm05cxIDxcFUCMw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762556843; c=relaxed/simple; bh=IFrW/8wkEFTdJsCV1ajusTiEZ/ACUDMTmryjdfd0HUY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=B5VktHxGlXsXl3XaPV4sj9vkjtt0NMZpKAQhLLnnWylDTWH/eb96XQeEGnNcYVnv4gTrzBf/2zJ7FZT/ESW4AULYrpZbkLZ7rzV2WDeNcJopPN9UOQJD2V4Aoea8u+yzIPIwB3lHalr1jRhBgtGwo8C+j7XClM1QABSHArmstYY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=bXuC5v+Z; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="bXuC5v+Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85D4CC4CEF7; Fri, 7 Nov 2025 23:07:21 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="bXuC5v+Z" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1762556839; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=dpCcvvXDvS225r6ycN7BEql+i73c6ph5/3/xeWgcF0A=; b=bXuC5v+ZHX2GjEVgHpDubrR5y7TOoo0dDdozLMuhmSnjwQVNpwAxtibWrLOKj0XN1OTuyv cvaTz5sFJafYzCUryCP+xJHfummxM7+YXyaPdVEZgsoh01zYzSt8ys2UnBW/jjLn9ayhmh tGzQwYU+tI1vKvFPrCmWIHFtKLma534= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 559a4b8e (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Fri, 7 Nov 2025 23:07:19 +0000 (UTC) Date: Sat, 8 Nov 2025 00:07:13 +0100 From: "Jason A. Donenfeld" To: Thiago Macieira 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. Message-ID: References: <1903914.sHLxoZxqIA@tjmaciei-mobl5> <2790505.9o76ZdvQCi@tjmaciei-mobl5> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2790505.9o76ZdvQCi@tjmaciei-mobl5> Hi Thiago, On Fri, Nov 07, 2025 at 11:55:35AM -0800, Thiago Macieira wrote: > 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. Oh. "Entropy source draining" is not a real thing. There used to be bizarre behavior related to /dev/random (not urandom), but this has been gone for ages. And even the non-getrandom Linux fallback code uses /dev/urandom before /dev/random. So not even on old kernels is this an issue. You can keep generating random numbers forever without worrying about running out of juice or irritating other processes. Jason