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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26E71C433DB for ; Mon, 8 Feb 2021 15:02:32 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 7D42164EB7 for ; Mon, 8 Feb 2021 15:02:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D42164EB7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id CCD8B4B5A0; Mon, 8 Feb 2021 10:02:30 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vq+HO1CqLxVc; Mon, 8 Feb 2021 10:02:28 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id AA1354B590; Mon, 8 Feb 2021 10:02:28 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 471894B590 for ; Mon, 8 Feb 2021 10:02:27 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 60OOVUYhsb+P for ; Mon, 8 Feb 2021 10:02:26 -0500 (EST) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 4C73C4B14E for ; Mon, 8 Feb 2021 10:02:26 -0500 (EST) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 166F264E29; Mon, 8 Feb 2021 15:02:25 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1l983S-00CoV5-QY; Mon, 08 Feb 2021 15:02:23 +0000 MIME-Version: 1.0 Date: Mon, 08 Feb 2021 15:02:22 +0000 From: Marc Zyngier To: Will Deacon Subject: Re: [PATCH v7 00/23] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth In-Reply-To: <20210208143248.GA25934@willie-the-truck> References: <20210208095732.3267263-1-maz@kernel.org> <20210208143248.GA25934@willie-the-truck> User-Agent: Roundcube Webmail/1.4.10 Message-ID: <240a0245f75d8368a4d90a5e6740dc7d@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: will@kernel.org, psodagud@codeaurora.org, sramana@codeaurora.org, catalin.marinas@arm.com, marcan@marcan.st, linux-kernel@vger.kernel.org, ardb@kernel.org, pajay@qti.qualcomm.com, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: Srinivas Ramana , Catalin Marinas , Hector Martin , linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, Ajay Patil , Prasad Sodagudi , kernel-team@android.com, Ard Biesheuvel , linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Will, On 2021-02-08 14:32, Will Deacon wrote: > Hi Marc, > > On Mon, Feb 08, 2021 at 09:57:09AM +0000, Marc Zyngier wrote: >> It recently came to light that there is a need to be able to override >> some CPU features very early on, before the kernel is fully up and >> running. The reasons for this range from specific feature support >> (such as using Protected KVM on VHE HW, which is the main motivation >> for this work) to errata workaround (a feature is broken on a CPU and >> needs to be turned off, or rather not enabled). >> >> This series tries to offer a limited framework for this kind of >> problems, by allowing a set of options to be passed on the >> command-line and altering the feature set that the cpufeature >> subsystem exposes to the rest of the kernel. Note that this doesn't >> change anything for code that directly uses the CPU ID registers. > > I applied this locally, but I'm seeing consistent boot failure under > QEMU when > KASAN is enabled. I tried sprinkling some __no_sanitize_address > annotations > around (see below) but it didn't help. The culprit appears to be > early_fdt_map(), but looking a bit more closely, I'm really nervous > about the > way we call into C functions from __primary_switched. Remember -- this > code > runs _twice_ when KASLR is active: before and after the randomization. > This > also means that any memory writes the first time around can be lost due > to > the D-cache invalidation when (re-)creating the kernel page-tables. Well, we already call into C functions with KASLR, and nothing explodes with that, so I must be doing something else wrong. I do have cache maintenance for the writes to the shadow registers, so that part should be fine. But I think I'm missing some cache maintenance around the FDT base itself, and I wonder what happens when we go around the loop. I'll chase this down now. Thanks for the heads up. M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm