From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) (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 37513145FFF for ; Wed, 25 Sep 2024 21:09:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727298590; cv=none; b=GB6jxBWR0MyzadCpG2vk1RVc0TY3WtQgdTK9voNp7ylOmw3HKN6XIh/o0EtZ8bFNlhfGM0XAJ8pxysYJfnU1OEkq8hIYEAdEHJi9RV53a/jW+J4lna+Soe9tWcXGVaulaBily7m0EhYT5KonVijHMeMTXyT+C8vIoeoRxbtWv/k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727298590; c=relaxed/simple; bh=ltJU61g0F1kiJyay/V4sLGhXkraR2ot+HlyaNfiBreE=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=tY4HEyCSLEEHRUSRgDw0w+FFEGuc+MWiLim+baOELapi6qH1YaKH9zNs/d03clL2hkjDIwVllyL8wRcwpcP144mOlyRyiMcOHL6GtpTADoZxzH6nfGA7nJN8SquUgDNf+kJiiLi86gyQrm+E9eBMCRw2r8J8TFM8vxi6zn6E89E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=E3cBsnqf; arc=none smtp.client-ip=192.198.163.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="E3cBsnqf" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1727298588; x=1758834588; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=ltJU61g0F1kiJyay/V4sLGhXkraR2ot+HlyaNfiBreE=; b=E3cBsnqfqLA2R+IvMK/9TxHpCe6Flsam01KeL5bfV2gEmu0osPJZBGLp HYWdt+kh/5/uhdkMZ9A9Yf63baba12cn3/CPh4OfyjmU16CizN2GK1hMo BWk2rVZicpicMATKr3fE3yc5PIHSAOCfse9P/wXCoYCbBhjRXMDJZ9tfj S+ePkpOCInSz7Nokt/0meCbtq7YEOyRMP9RsoMFMM6i4qEcJDC3PJbHze wMQyKKN7vZzH0+MPlpqrPL/BP2298/DwbDS7TQR+BfmAqJb9d1w2/NkG4 Tae2fo6nnwZ+ypvyUlhNjSDHTsRxC8rIxq8IzBpgrK9WSSfCiHcxt85EE A==; X-CSE-ConnectionGUID: WrxCIWLlR1WE1kLIzWOjGA== X-CSE-MsgGUID: os9SCyMoQOqjv1vu6/fmwg== X-IronPort-AV: E=McAfee;i="6700,10204,11206"; a="26235405" X-IronPort-AV: E=Sophos;i="6.10,258,1719903600"; d="scan'208";a="26235405" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Sep 2024 14:09:11 -0700 X-CSE-ConnectionGUID: qlQst7lHQbC5667tIj4vXA== X-CSE-MsgGUID: xukS9XTvTV2/dpDf0CJANA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.10,258,1719903600"; d="scan'208";a="71998838" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.54.38.190]) by orviesa009.jf.intel.com with ESMTP; 25 Sep 2024 14:09:11 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id 2063930183B; Wed, 25 Sep 2024 14:09:11 -0700 (PDT) From: Andi Kleen To: Ard Biesheuvel Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel , x86@kernel.org, "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Uros Bizjak , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , Paolo Bonzini , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , Arnaldo Carvalho de Melo , Namhyung Kim Subject: Re: [RFC PATCH 25/28] x86: Use PIE codegen for the core kernel In-Reply-To: <20240925150059.3955569-55-ardb+git@google.com> (Ard Biesheuvel's message of "Wed, 25 Sep 2024 17:01:25 +0200") References: <20240925150059.3955569-30-ardb+git@google.com> <20240925150059.3955569-55-ardb+git@google.com> Date: Wed, 25 Sep 2024 14:09:11 -0700 Message-ID: <87ikuj30g8.fsf@linux.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Ard Biesheuvel writes: > This substantially reduces the number of relocations that need to be > processed when booting a relocatable KASLR kernel. > > Before (size in bytes of the reloc table): > > 797372 arch/x86/boot/compressed/vmlinux.relocs > > After: > > 400252 arch/x86/boot/compressed/vmlinux.relocs I don't know why anybody would care about the size of the relocation table? What matters is what it does to general performance. Traditionally even on x86-64 PIC/E has a cost and the kernel model was intended to avoid that. >From my perspective this patch kit doesn't fix a real problem, it's all risk of performance regression with no gain. -Andi