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[2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id w13-20020ac843cd000000b0042c3cf56d1csi5733236qtn.65.2024.02.14.11.58.54 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Feb 2024 11:58:54 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-65905-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@zx2c4.com header.s=20210105 header.b=bAb38AmS; arc=pass (i=1 dkim=pass dkdomain=zx2c4.com); spf=pass (google.com: domain of linux-kernel+bounces-65905-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-65905-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=zx2c4.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 7B4E71C262E2 for ; Wed, 14 Feb 2024 19:58:54 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1331E13F005; Wed, 14 Feb 2024 19:58:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="bAb38AmS" 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 806BA13DB93; Wed, 14 Feb 2024 19:58:04 +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=1707940684; cv=none; b=cvb55fey+6/3xCocpxfLbQ2sjy+uk22lAfwFtsvhn3MkPWR8tjscSNCX47dW5cMk58opnfDPuM6a1pDtJJsKakVpVHli4DqV5hK4Xsa2uLjuKcY7w1lqavoSSlZyNMjHizyvq769FGjZbeegAhxzG9Ov7xogbYm5D2NzE82DF1U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707940684; c=relaxed/simple; bh=rTKv1TDsFzL+RzB4KD1Ng3M4meMkWcKDfmVZOO+HcO0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ZyjDcdlvQB4tSNCtV17EnaDtx4QIuwzzSmpAeOLJv4HQf4/4At+kMded0D3li/foIivQwH56fHUj1KtnyVi0bMCUlijJ3me1esUTrMg0M87POOnsNTq1CfRGJUDr+3K+pMm3LGNruwgprZsg5QR82m5B5E3ZSojeS1xk10RO0K4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=bAb38AmS; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEBC6C433C7; Wed, 14 Feb 2024 19:58:02 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="bAb38AmS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1707940681; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=usBdTDKhZdYOqvFmhLJXleA6TJU1AAI9ITba9p7Xy2A=; b=bAb38AmSl+1HLYBs2tbYWtbKGdv9rc3fEuKOzyVp0l7GFm/kfZx+r+PPndQPtqIXwI7cNI j61OF/Fd8BmYNgjSAkZSMMp4nf8hfN2aaib+LKY/lpjm0SOTTInPqsfck2j68ybarrZ0ft S8lroiEzKdWeQxtpE95tgCewvP2Y2Co= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id a632d9c0 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Wed, 14 Feb 2024 19:58:01 +0000 (UTC) From: "Jason A. Donenfeld" To: x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , Borislav Petkov , =?utf-8?q?Daniel_P_=2E_Berrang=C3=A9?= , Dave Hansen , Elena Reshetova , "H . Peter Anvin" , Ingo Molnar , "Kirill A . Shutemov" , Theodore Ts'o , Thomas Gleixner Subject: [PATCH v2 1/2] x86/archrandom: WARN if RDRAND fails and don't retry Date: Wed, 14 Feb 2024 20:56:47 +0100 Message-ID: <20240214195744.8332-2-Jason@zx2c4.com> In-Reply-To: <20240214195744.8332-1-Jason@zx2c4.com> References: <20240214195744.8332-1-Jason@zx2c4.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790905664069293898 X-GMAIL-MSGID: 1790905664069293898 According to both Intel [1] and AMD [2], RDRAND will never fail unless the hardware is defective. The old advice to try 10 times is not considered correct. RDSEED is a different story. But with RDRAND never failing, WARN()ing when it does seems like a reasonable thing to do, as it's probably indicative of some deeper problem. [1] https://lore.kernel.org/all/DM8PR11MB57503A2BB6F74618D64CC44AE74E2@DM8PR11MB5750.namprd11.prod.outlook.com/ [2] https://lore.kernel.org/all/20240209214530.GHZcac-vOym8k3IuJm@fat_crate.local/ Cc: Borislav Petkov Cc: Daniel P. Berrangé Cc: Dave Hansen Cc: Elena Reshetova Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Kirill A. Shutemov Cc: Theodore Ts'o Cc: Thomas Gleixner Signed-off-by: Jason A. Donenfeld --- arch/x86/include/asm/archrandom.h | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h index 02bae8e0758b..1cc01ecd5e75 100644 --- a/arch/x86/include/asm/archrandom.h +++ b/arch/x86/include/asm/archrandom.h @@ -13,22 +13,18 @@ #include #include -#define RDRAND_RETRY_LOOPS 10 - /* Unconditional execution of RDRAND and RDSEED */ static inline bool __must_check rdrand_long(unsigned long *v) { bool ok; - unsigned int retry = RDRAND_RETRY_LOOPS; - do { - asm volatile("rdrand %[out]" - CC_SET(c) - : CC_OUT(c) (ok), [out] "=r" (*v)); - if (ok) - return true; - } while (--retry); - return false; + asm volatile("rdrand %[out]" + CC_SET(c) + : CC_OUT(c) (ok), [out] "=r" (*v)); +#ifndef KASLR_COMPRESSED_BOOT + WARN_ON(!ok); +#endif + return ok; } static inline bool __must_check rdseed_long(unsigned long *v)