From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 72973C636BC for ; Sun, 22 Feb 2026 21:34:35 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4fJy1P6lzzz2xMt; Mon, 23 Feb 2026 08:34:33 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip="2600:3c04:e001:324:0:1991:8:25" ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1771796073; cv=none; b=TDkyBeK4eztZB+zPr0w15KPETadMGUybDRaJaNsqog0tCZF2wIUjxi8X2GHGbgwyRvE/jv2VGc+O5x+SLNRJiMs0Txsddfc7Bvv6/mHd4QBuiXCwluAnuishwzMqLoebXr/eH+N0P3ACYa5/Yp8o/ZDQ9BSzKIf/jEGmaGy+6kizeBCB/T3BIJHPBpZaqBXPBOfN5O0MWT1NQ3O/F4vyLf4AsNvhxH2POZFXWkJEFk4IC8SjnJdcOz3mdkHLj0Jz5fv+LrEC5ubvjoXGq4Gh2ly8+XalrSkk5duWkLmF9G9PCVuiLH4sS0hfQPRbfSizY1ZmS2vRtokCkZzC+ri/ZQ== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1771796073; c=relaxed/relaxed; bh=EmvFoagq4laq5CsfLkxqtnL3auTtxR8uqVSGiltKyEI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=blKSQNRNvA/3FRf/PV6Z39ucjN5uZs8Ap1ZwBfUfoupRvvW07FkQY0RWOUEubp9FfCUXVymoIaJltje1lAO/8MWchqWsA5QbDYjIZ0ZgNQpRiwzgJ2yAWMs0+j0fxWFNKHafCEXF6O6xpgJeB8m+oo5cp7sIKKLWxNZtmXNFHhB8NH1hB0MQmjj5wPoTIw0K15UQAQtYQy1LHQlRmtKCDYgBDppAJrFLS8NMU1jaLpdzMlG9YMxLe2bMpBkIbYhrCqXWxsr/HF+DZ2oiN1pji5sBUY+JDuc1aROAvRJcRygRXRGeF4ZPyaORfeLwp1cWOvhiN426HkXI4Snj5Fqk8A== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=F3kE5G5Y; dkim-atps=neutral; spf=pass (client-ip=2600:3c04:e001:324:0:1991:8:25; helo=tor.source.kernel.org; envelope-from=tglx@kernel.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=F3kE5G5Y; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=2600:3c04:e001:324:0:1991:8:25; helo=tor.source.kernel.org; envelope-from=tglx@kernel.org; receiver=lists.ozlabs.org) Received: from tor.source.kernel.org (tor.source.kernel.org [IPv6:2600:3c04:e001:324:0:1991:8:25]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4fJy1P24Hxz2xGF for ; Mon, 23 Feb 2026 08:34:33 +1100 (AEDT) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 899A460121; Sun, 22 Feb 2026 21:34:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3118FC116D0; Sun, 22 Feb 2026 21:34:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771796070; bh=MoM4gAfGlJ1ngKCroMgt6s8hQQRUOv2GP6lsvWBTYTk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=F3kE5G5YSHiCVZ5mOwWBQ1EmkdZUUxri8FWvUUe1+bPk6Car0R0kut2uvNuYHVkAa g8IvAYcI7E8/6hHCb/jrPziQTKClMwrJ6H0Y/aYHLJyimbtr/frfU8CLViovCDA9UV HIObLbqEucr9FrLIbWX5/hRoPhPnR0+zxQyrVmCTdNaMIGloFGLnnqKAP5W6Ewm6w7 I/owa0GiWqAQBaI4TmPdDfE67f10RHZ+BDAgtt/1JTGJALkdfXpJeUzGxFHrjR/KHe NiTE6uiB4kCm6q8SZrGgK2AZmAXo4GAErDwos4utQpdh9gKlK0o0vXjumdP0UVYmSi KhiPc2AZqyPxQ== From: Thomas Gleixner To: Ryan Roberts , Catalin Marinas , Will Deacon , Huacai Chen , Madhavan Srinivasan , Michael Ellerman , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Ingo Molnar , Borislav Petkov , Dave Hansen , Kees Cook , "Gustavo A. R. Silva" , Arnd Bergmann , Mark Rutland , "Jason A. Donenfeld" , Ard Biesheuvel , Jeremy Linton , David Laight Cc: Ryan Roberts , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v4 3/3] randomize_kstack: Unify random source across arches In-Reply-To: <20260119130122.1283821-4-ryan.roberts@arm.com> References: <20260119130122.1283821-1-ryan.roberts@arm.com> <20260119130122.1283821-4-ryan.roberts@arm.com> Date: Sun, 22 Feb 2026 22:34:26 +0100 Message-ID: <87ecmcwjh9.ffs@tglx> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain On Mon, Jan 19 2026 at 13:01, Ryan Roberts wrote: > I tested an earlier version of this change on x86 bare metal and it > showed a smaller but still significant improvement. The bare metal > system wasn't available this time around so testing was done in a VM > instance. I'm guessing the cost of rdtsc is higher for VMs. No it's not, unless the hypervisor traps RDTSC, which would be insane as that would cause massive regressions all over the place. So guessing is not really helpful if you want to argue performance. Thanks, tglx