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[209.132.180.67]) by mx.google.com with ESMTP id j9si3497019pgh.206.2019.05.03.11.39.05; Fri, 03 May 2019 11:39:20 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@amacapital-net.20150623.gappssmtp.com header.s=20150623 header.b=cGF3AP4t; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728342AbfECQkn (ORCPT + 99 others); Fri, 3 May 2019 12:40:43 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:45072 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727780AbfECQkm (ORCPT ); Fri, 3 May 2019 12:40:42 -0400 Received: by mail-pl1-f193.google.com with SMTP id o5so2934587pls.12 for ; Fri, 03 May 2019 09:40:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amacapital-net.20150623.gappssmtp.com; s=20150623; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=wO+jnW70s0cmOTXg4iOs5E+w567bkWpBLIgvBYRMCxM=; b=cGF3AP4tRiCgQyFVUzz9dmLwmzg/EKlZu0Io9Quu+YlZukBQo4VPWnSafapLdH6wiK tCKauzUcit5AeZX5tmEU/REVUQrsqsXh8BvYW/wEwsVb8n3WDXijDdWXep5L2fcnZjuo F7JK69WTo6QgfZmAkd+sZfytfC9nkIkEWSxzSgXcKHSA1VIkWXszvQ53/xHR+kl+a4Nq SmGPeFa6/bG80pkUtxBu0awmqA0d2UiZxBAV6iy8LR3GX5i2iB3zibWajEvpGMOM1hSH aukbBHcmBS8qeJCofwboAtg32svSvvnMMCUTBgnD+y4T5It9L/u2qJq0SbuMVwe9A8mK NYFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=wO+jnW70s0cmOTXg4iOs5E+w567bkWpBLIgvBYRMCxM=; b=hDsqSt04KHXEHNdNQBcT+1qyw2JLr2TQJmtdPbjPhwmOHi7nlC+5VqcKrxrLHXXteq Gomj7OmlqSQ+2alCLtx7Zm31dVJ3mP4hcpFTXvyJoz0gl9aEqgrg05368kRazZk0UThb KfDkALfht86siirz0mY6qT9qpJV80gj+pTimEH/PDbsKNKOsTEi0k+QJbwnFDaX7W5WE YVUnyP5RX4dSOEykl/M6p8ZtX/9+7PzyFHTnyEo3Ii+A76UlwvVKdkKfm+5Iy5MVoTnr whV5WAAWgyFQfwfM2BBi0f1Ul0xb/g0b9I4AupNhAzN359O+Dn2f5LvTZd/kEGTFy1Ll hP5w== X-Gm-Message-State: APjAAAUn51qGmeEYBWMeb8t3WzrucFSpt60vOl/GhwIGBLkdMSK3YKj1 7zhdmPOQOkgnUYB6NAs+nL1oeA== X-Received: by 2002:a17:902:6ac6:: with SMTP id i6mr11650609plt.313.1556901642168; Fri, 03 May 2019 09:40:42 -0700 (PDT) Received: from [10.145.97.154] ([12.53.65.170]) by smtp.gmail.com with ESMTPSA id a6sm3539309pfn.181.2019.05.03.09.40.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 May 2019 09:40:40 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] x86/entry/64: randomize kernel stack offset upon syscall From: Andy Lutomirski X-Mailer: iPhone Mail (16E227) In-Reply-To: <20190502164325.GA115950@gmail.com> Date: Fri, 3 May 2019 09:40:40 -0700 Cc: Andy Lutomirski , David Laight , "Reshetova, Elena" , Theodore Ts'o , Eric Biggers , "ebiggers@google.com" , "herbert@gondor.apana.org.au" , Peter Zijlstra , "keescook@chromium.org" , Daniel Borkmann , "linux-kernel@vger.kernel.org" , "jpoimboe@redhat.com" , "jannh@google.com" , "Perla, Enrico" , "mingo@redhat.com" , "bp@alien8.de" , "tglx@linutronix.de" , "gregkh@linuxfoundation.org" , "Edgecombe, Rick P" , Linus Torvalds , Peter Zijlstra Content-Transfer-Encoding: quoted-printable Message-Id: <5DD37CAB-2197-42EC-9D27-5DF924EED22B@amacapital.net> References: <57357E35-3D9B-4CA7-BAB9-0BE89E0094D2@amacapital.net> <2236FBA76BA1254E88B949DDB74E612BA4C66A8A@IRSMSX102.ger.corp.intel.com> <6860856C-6A92-4569-9CD8-FF6C5C441F30@amacapital.net> <2236FBA76BA1254E88B949DDB74E612BA4C6A4D7@IRSMSX102.ger.corp.intel.com> <303fc4ee5ac04e4fac104df1188952e8@AcuMS.aculab.com> <2236FBA76BA1254E88B949DDB74E612BA4C6C2C3@IRSMSX102.ger.corp.intel.com> <2e55aeb3b39440c0bebf47f0f9522dd8@AcuMS.aculab.com> <20190502150853.GA16779@gmail.com> <20190502164325.GA115950@gmail.com> To: Ingo Molnar Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On May 2, 2019, at 9:43 AM, Ingo Molnar wrote: >=20 >=20 > * Andy Lutomirski wrote: >=20 >>> 8 gigabits/sec sounds good throughput in principle, if there's no >>> scalability pathologies with that. >>=20 >> The latency is horrible. >=20 > Latency would be amortized via batching anyway, so 8 gigabits/sec=20 > suggests something on the order of magnitude of 4 bits per cycle, right?=20= > With 64 bits extraction at a time that would be 16 cycles per 64-bit=20 > word, which isn't too bad, is it? I haven=E2=80=99t really dug in, but some Googling suggests that the 8Gbps f= igure is what you get with all cores doing RDRAND. It sounds like the actua= l RDRAND instruction doesn=E2=80=99t pipeline. > Making it "optional" is not really a technical argument in any way=20 > though, either distros enable it in which case it's a de-facto default=20 > setting, or they don't, in which case it de-facto almost doesn't exist. >=20 >=20 True.=