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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 F2D33CA9EC9 for ; Mon, 4 Nov 2019 21:44:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0CF920848 for ; Mon, 4 Nov 2019 21:44:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pHQfGMcF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729689AbfKDVon (ORCPT ); Mon, 4 Nov 2019 16:44:43 -0500 Received: from mail-ua1-f65.google.com ([209.85.222.65]:38627 "EHLO mail-ua1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728634AbfKDVon (ORCPT ); Mon, 4 Nov 2019 16:44:43 -0500 Received: by mail-ua1-f65.google.com with SMTP id u99so5470700uau.5 for ; Mon, 04 Nov 2019 13:44:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kaXvf9wE3k9UaecG65PnRrmHU9a0z9eeJYq+CJlozEg=; b=pHQfGMcFvDs8Sz/sj2D9FDXz3MnOQRQu+N4CdnI6FNzotw2uFLAsGlw2AfCslqt5i1 NhuT8B5Ezfwhp9svCCthVzKrqQzSaREP2/BOyA4VdDO3mOGFMeEnNqjZV9EKKb5BwgAH bM/dxgbkeGBwpw6v8NjWHN7WfR5TQqN/xXvS5kz11espcMoT6/ho31I/XOxv81JBcV1z GeqbggJuYjxj2QeyalY3/MCFCfCDWJn8/AxC+ZFPpCHvzX/Cpnxf1nw4yPeZBVh+ScLp O8nGwga8BiVRzIj9L+z7DaZgwmXUgoNZyiEQqIULFC5kXaLbkCP27rPqGbTAVSPqhK1Q tN3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=kaXvf9wE3k9UaecG65PnRrmHU9a0z9eeJYq+CJlozEg=; b=pw85w+UJJW7EwfDR36rUuhDvNoBqU5654RZC08wpQ9HN/WIG4jq87LZVM2gG6gWZ7E 4+7hTnY2T4k2MNWyNDrjiBddoRvs+kA9hVAHm3vonYZ52ejb0RGIPHbgGStGclq6dkUJ TLoezRK0uSfjw+henWgWAoUqknWUtsagGye0RqDNDwMKQ4ZXw6et2UB/oO3DPVXaK2qy h5iuhSYRakpfFAHwxp/jELtp5m2E7vyVCaGyjqRsyEppNjN+xRTM5bvnIphsFPcCEmMr HkeDbpnIF9BM/xtD2rqKJ4lGqXfRM1aSdUoFHREz99hJYYkZWTirj/nOUWzE9OGt8qSD f1ZA== X-Gm-Message-State: APjAAAXFELOFzea8TmKoRoaAgy1ttYmEvI5HSgafW8zPT7kuR31biVWU /dKrt+/GEC0pm67Lr1bHTlc6AWzppYTXfrKyi3mprQ== X-Google-Smtp-Source: APXvYqyozZ81Thh7mlXHgf1QUiqKh64ERV1FrTZSir+nNNiHAQ72oavyDPOWqxJDAI6llfn+2fNkSSVjyIyFG0syB7k= X-Received: by 2002:ab0:5981:: with SMTP id g1mr1829842uad.98.1572903881724; Mon, 04 Nov 2019 13:44:41 -0800 (PST) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191101221150.116536-1-samitolvanen@google.com> <20191101221150.116536-4-samitolvanen@google.com> <20191104115138.GB45140@lakrids.cambridge.arm.com> In-Reply-To: <20191104115138.GB45140@lakrids.cambridge.arm.com> From: Sami Tolvanen Date: Mon, 4 Nov 2019 13:44:30 -0800 Message-ID: Subject: Re: [PATCH v4 03/17] arm64: kvm: stop treating register x18 as caller save To: Mark Rutland Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux , Kernel Hardening , linux-arm-kernel , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 4, 2019 at 3:51 AM Mark Rutland wrote: > > --- a/arch/arm64/kvm/hyp/entry.S > > +++ b/arch/arm64/kvm/hyp/entry.S > > @@ -23,6 +23,7 @@ > > .pushsection .hyp.text, "ax" > > > > Could we please add a note here, e.g. > > /* > * We treat x18 as callee-saved as the host may use it as a platform > * register (e.g. for shadow call stack). > */ > > ... as that will avoid anyone trying to optimize this away in future > after reading the AAPCS. Sure, that's a good idea. > > .macro restore_callee_saved_regs ctxt > > + // We assume \ctxt is not x18-x28 > > Probably worth s/assume/require/ here. Agreed, I'll change this in v5. Sami