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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CC54C4332F for ; Mon, 21 Nov 2022 19:08:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231164AbiKUTI2 (ORCPT ); Mon, 21 Nov 2022 14:08:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229985AbiKUTIY (ORCPT ); Mon, 21 Nov 2022 14:08:24 -0500 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7CC5FD28AA for ; Mon, 21 Nov 2022 11:08:23 -0800 (PST) Received: from zn.tnic (p200300ea9733e725329c23fffea6a903.dip0.t-ipconnect.de [IPv6:2003:ea:9733:e725:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id C30691EC03EA; Mon, 21 Nov 2022 20:08:21 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1669057701; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=PW/HmTfWd3KD7F9AeG0CHyci/txJYNIbKWWtUh/bG0A=; b=KY/hVSo/pMHtM24iKKP8OWuqQqgIXSOiCgSokHrbPb09ujtI5tpWNpwdkF2vfLeYOGDu+q MIh/+eWlfr3v792+e+VBh1CWiad8a8H7XnceWO27O7Pi+LUuJqiPOGRc4WTm8DtuycmzSC IeofWwBGS3FS4JHqpbJFflIaGoppcmk= Date: Mon, 21 Nov 2022 20:08:21 +0100 From: Borislav Petkov To: Juergen Gross Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar , Dave Hansen , "H. Peter Anvin" Subject: Re: [PATCH] x86/boot: skip realmode init code when running as Xen PV guest Message-ID: References: <20221121162433.28070-1-jgross@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221121162433.28070-1-jgross@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 21, 2022 at 05:24:33PM +0100, Juergen Gross wrote: > When running as a Xen PV guest there is no need for setting up the > realmode trampoline, as realmode isn't supported in this environment. > > Trying to setup the trampoline has been proven to be problematic in > some cases, especially when trying to debug early boot problems with > Xen requiring to keep the EFI boot-services memory mapped (some > firmware variants seem to claim basically all memory below 1M for boot > services). > > Skip the trampoline setup code for Xen PV guests. > > Fixes: 084ee1c641a0 ("x86, realmode: Relocator for realmode code") > Signed-off-by: Juergen Gross > --- > arch/x86/include/asm/realmode.h | 4 ++-- > arch/x86/realmode/init.c | 3 +++ > 2 files changed, 5 insertions(+), 2 deletions(-) > diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h > index fd6f6e5b755a..5bfce58f1bab 100644 > --- a/arch/x86/include/asm/realmode.h > +++ b/arch/x86/include/asm/realmode.h > @@ -78,8 +78,8 @@ extern unsigned char secondary_startup_64_no_verify[]; > > static inline size_t real_mode_size_needed(void) > { > - if (real_mode_header) > - return 0; /* already allocated. */ > + if (real_mode_header || cpu_feature_enabled(X86_FEATURE_XENPV)) > + return 0; /* already allocated or not needed. */ > > return ALIGN(real_mode_blob_end - real_mode_blob, PAGE_SIZE); > } > diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c > index 41d7669a97ad..1826700b156e 100644 > --- a/arch/x86/realmode/init.c > +++ b/arch/x86/realmode/init.c > @@ -202,6 +202,9 @@ static void __init set_real_mode_permissions(void) > > static int __init init_real_mode(void) > { > + if (cpu_feature_enabled(X86_FEATURE_XENPV))a This reminds me of the notorious if (xen) sprinkling from years ago. Please don't do that. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette