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 7DFAEC77B7C for ; Fri, 26 May 2023 04:24:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236042AbjEZEYN (ORCPT ); Fri, 26 May 2023 00:24:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233300AbjEZEYM (ORCPT ); Fri, 26 May 2023 00:24:12 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DACA010CE for ; Thu, 25 May 2023 21:23:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685074978; 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: in-reply-to:in-reply-to:references:references; bh=U2epE74rgQGpSbchmdCJa1fM29pXtiET/OfLMRsBcJc=; b=gMe65Uf/HTh0/L6C+V+P+y2zp7zgt9Qj3PwyuOdz1btL+y2jGmbeVIwWvGj0/KgjmxhU9f GQtmuY+yeltTKqa65cyyZix6xTyVdVBX7i3jK5KEiIuB4wTeXypEyCjKwk7fUecEdgSLpe jTNo8clDIrkn56qCKKwasAJk1IVhsyI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-674-S2A3ZgtOOM-QvBWPx5kFIw-1; Fri, 26 May 2023 00:22:56 -0400 X-MC-Unique: S2A3ZgtOOM-QvBWPx5kFIw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BAB5185A5A8; Fri, 26 May 2023 04:22:55 +0000 (UTC) Received: from localhost (ovpn-12-35.pek2.redhat.com [10.72.12.35]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 080F52166B2B; Fri, 26 May 2023 04:22:54 +0000 (UTC) Date: Fri, 26 May 2023 12:22:51 +0800 From: Baoquan He To: Tao Liu Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, Ard Biesheuvel , dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, dyoung@redhat.com, kexec@lists.infradead.org, linux-efi@vger.kernel.org Subject: Re: [PATCH] x86/kexec: Add EFI config table identity mapping for kexec kernel Message-ID: References: <20230525094914.23420-1-ltao@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230525094914.23420-1-ltao@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org Add Ard to CC. On 05/25/23 at 05:49pm, Tao Liu wrote: > A kexec kernel bootup hang is observed on Intel Atom cpu due to unmapped > EFI config table. > > Currently EFI system table is identity-mapped for the kexec kernel, but EFI > config table is not mapped explicitly: > > commit 6bbeb276b71f ("x86/kexec: Add the EFI system tables and ACPI > tables to the ident map") > > Later in the following 2 commits, EFI config table will be accessed when > enabling sev at kernel startup. This may result in a page fault due to EFI > config table's unmapped address. Since the page fault occurs at an early > stage, it is unrecoverable and kernel hangs. > > commit ec1c66af3a30 ("x86/compressed/64: Detect/setup SEV/SME features > earlier during boot") > commit c01fce9cef84 ("x86/compressed: Add SEV-SNP feature > detection/setup") > > In addition, the issue doesn't appear on all systems, because the kexec > kernel uses Page Size Extension (PSE) for identity mapping. In most cases, > EFI config table can end up to be mapped into due to 1 GB page size. > However if nogbpages is set, or cpu doesn't support pdpe1gb feature > (e.g Intel Atom x6425RE cpu), EFI config table may not be mapped into > due to 2 MB page size, thus a page fault hang is more likely to happen. > > In this patch, we will make sure the EFI config table is always mapped. > > Signed-off-by: Tao Liu > --- > arch/x86/kernel/machine_kexec_64.c | 35 ++++++++++++++++++++++++++---- > 1 file changed, 31 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c > index 1a3e2c05a8a5..755aa12f583f 100644 > --- a/arch/x86/kernel/machine_kexec_64.c > +++ b/arch/x86/kernel/machine_kexec_64.c > @@ -28,6 +28,7 @@ > #include > #include > #include > +#include > > #ifdef CONFIG_ACPI > /* > @@ -86,10 +87,12 @@ const struct kexec_file_ops * const kexec_file_loaders[] = { > #endif > > static int > -map_efi_systab(struct x86_mapping_info *info, pgd_t *level4p) > +map_efi_sys_cfg_tab(struct x86_mapping_info *info, pgd_t *level4p) > { > #ifdef CONFIG_EFI > unsigned long mstart, mend; > + void *kaddr; > + int ret; > > if (!efi_enabled(EFI_BOOT)) > return 0; > @@ -105,6 +108,30 @@ map_efi_systab(struct x86_mapping_info *info, pgd_t *level4p) > if (!mstart) > return 0; > > + ret = kernel_ident_mapping_init(info, level4p, mstart, mend); > + if (ret) > + return ret; > + > + kaddr = memremap(mstart, mend - mstart, MEMREMAP_WB); > + if (!kaddr) { > + pr_err("Could not map UEFI system table\n"); > + return -ENOMEM; > + } > + > + mstart = efi_config_table; > + > + if (efi_enabled(EFI_64BIT)) { > + efi_system_table_64_t *stbl = (efi_system_table_64_t *)kaddr; > + > + mend = mstart + sizeof(efi_config_table_64_t) * stbl->nr_tables; > + } else { > + efi_system_table_32_t *stbl = (efi_system_table_32_t *)kaddr; > + > + mend = mstart + sizeof(efi_config_table_32_t) * stbl->nr_tables; > + } > + > + memunmap(kaddr); > + > return kernel_ident_mapping_init(info, level4p, mstart, mend); > #endif > return 0; > @@ -244,10 +271,10 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable) > } > > /* > - * Prepare EFI systab and ACPI tables for kexec kernel since they are > - * not covered by pfn_mapped. > + * Prepare EFI systab, config table and ACPI tables for kexec kernel > + * since they are not covered by pfn_mapped. > */ > - result = map_efi_systab(&info, level4p); > + result = map_efi_sys_cfg_tab(&info, level4p); > if (result) > return result; > > -- > 2.33.1 >