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=-21.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 D7A14C4708F for ; Mon, 31 May 2021 09:59:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9D99611AC for ; Mon, 31 May 2021 09:59:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231360AbhEaKBP (ORCPT ); Mon, 31 May 2021 06:01:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:58290 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231514AbhEaKAb (ORCPT ); Mon, 31 May 2021 06:00:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 32D1F610A0; Mon, 31 May 2021 09:58:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622455129; bh=6kbI97vGAbBkOyOvwkIed49Ymrsa0Ja/+U28stuH/58=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=q5hje2ScELjyPNJ9u60mQwPa2LHxOC3LyIK9JffWZkotM/9/SREj3ZWBKtvou+TJi jtR412+hth7vV/h8rY0gvBdRu22jLKPx2YVzCD/AtOUPBgs99ORhHq9ARMnF1RMpin zoHAsBY+Sqez8qRxuCXI6r16XKvK4yMomUa7ijizLn2cjp1ryfaAMN0VqBOFBOAMfa 78Pw5b3r1pSOLd/ID1mgYtntD4Wm+i3W2k4+k0sNVuVE17Hh+oS0cpwDeyz3gEfs8/ rW5i69hqE/ldzZkRlFqsKw0C8zNm+AOioSnezo6ps7a6mOmI+IG5zCwKGbofAlPADE yZGRcbHssdxYw== Date: Mon, 31 May 2021 12:58:40 +0300 From: Mike Rapoport To: Borislav Petkov Cc: Lianbo Jiang , linux-kernel@vger.kernel.org, x86@kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, kexec@lists.infradead.org, ardb@kernel.org, dvhart@infradead.org, andy@infradead.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, luto@amacapital.net, bhe@redhat.com, dyoung@redhat.com Subject: Re: [PATCH v2] x86/efi: unconditionally hold the whole low-1MB memory regions Message-ID: References: <20210531090023.16471-1-lijiang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On Mon, May 31, 2021 at 11:08:32AM +0200, Borislav Petkov wrote: > + Mike. > > On Mon, May 31, 2021 at 05:00:23PM +0800, Lianbo Jiang wrote: > > Some sub-1MB memory regions may be reserved by EFI boot services, and the > > memory regions will be released later in the efi_free_boot_services(). > > > > Currently, always reserve all sub-1MB memory regions when the crashkernel > > option is specified, but unfortunately EFI boot services may have already > > reserved some sub-1MB memory regions before the crash_reserve_low_1M() is > > called, which makes that the crash_reserve_low_1M() only own the > > remaining sub-1MB memory regions, not all sub-1MB memory regions, because, > > subsequently EFI boot services will free its own sub-1MB memory regions. > > Eventually, DMA will be able to allocate memory from the sub-1MB area and > > cause the following error: > > > > crash> kmem -s |grep invalid > > kmem: dma-kmalloc-512: slab: ffffd52c40001900 invalid freepointer: ffff9403c0067300 > > kmem: dma-kmalloc-512: slab: ffffd52c40001900 invalid freepointer: ffff9403c0067300 > > crash> vtop ffff9403c0067300 > > VIRTUAL PHYSICAL > > ffff9403c0067300 67300 --->The physical address falls into this range [0x0000000000063000-0x000000000008efff] > > > > kernel debugging log: > > ... > > [ 0.008927] memblock_reserve: [0x0000000000010000-0x0000000000013fff] efi_reserve_boot_services+0x85/0xd0 > > [ 0.008930] memblock_reserve: [0x0000000000063000-0x000000000008efff] efi_reserve_boot_services+0x85/0xd0 > > ... > > [ 0.009425] memblock_reserve: [0x0000000000000000-0x00000000000fffff] crash_reserve_low_1M+0x2c/0x49 > > ... > > [ 0.010586] Zone ranges: > > [ 0.010587] DMA [mem 0x0000000000001000-0x0000000000ffffff] > > [ 0.010589] DMA32 [mem 0x0000000001000000-0x00000000ffffffff] > > [ 0.010591] Normal [mem 0x0000000100000000-0x0000000c7fffffff] > > [ 0.010593] Device empty > > ... > > [ 8.814894] __memblock_free_late: [0x0000000000063000-0x000000000008efff] efi_free_boot_services+0x14b/0x23b > > [ 8.815793] __memblock_free_late: [0x0000000000010000-0x0000000000013fff] efi_free_boot_services+0x14b/0x23b > > > > To fix the above issues, let's hold the whole low-1M memory regions > > unconditionally in the efi_free_boot_services(). > > > > Signed-off-by: Lianbo Jiang > > --- > > Background(copy from bhe's comment in the patch v1): > > > > Kdump kernel also need go through real mode code path during bootup. It > > is not different than normal kernel except that it skips the firmware > > resetting. So kdump kernel needs low 1M as system RAM just as normal > > kernel does. Here we reserve the whole low 1M with memblock_reserve() > > to avoid any later kernel or driver data reside in this area. Otherwise, > > we need dump the content of this area to vmcore. As we know, when crash > > happened, the old memory of 1st kernel should be untouched until vmcore > > dumping read out its content. Meanwhile, kdump kernel need reuse low 1M. > > In the past, we used a back up region to copy out the low 1M area, and > > map the back up region into the low 1M area in vmcore elf file. In > > 6f599d84231fd27 ("x86/kdump: Always reserve the low 1M when the crashkernel > > option is specified"), we changed to lock the whole low 1M to avoid > > writting any kernel data into, like this we can skip this area when > > dumping vmcore. > > > > Above is why we try to memblock reserve the whole low 1M. We don't want > > to use it, just don't want anyone to use it in 1st kernel. > > > > > > arch/x86/platform/efi/quirks.c | 32 +++++++++++++++----------------- > > 1 file changed, 15 insertions(+), 17 deletions(-) > > > > diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c > > index 7850111008a8..840b7e3b3d48 100644 > > --- a/arch/x86/platform/efi/quirks.c > > +++ b/arch/x86/platform/efi/quirks.c > > @@ -11,6 +11,7 @@ > > #include > > #include > > #include > > +#include > > > > #include > > #include > > @@ -409,7 +410,7 @@ void __init efi_free_boot_services(void) > > for_each_efi_memory_desc(md) { > > unsigned long long start = md->phys_addr; > > unsigned long long size = md->num_pages << EFI_PAGE_SHIFT; > > - size_t rm_size; > > + unsigned long long end = start + size; > > > > if (md->type != EFI_BOOT_SERVICES_CODE && > > md->type != EFI_BOOT_SERVICES_DATA) { > > @@ -431,23 +432,20 @@ void __init efi_free_boot_services(void) > > efi_unmap_pages(md); > > > > /* > > - * Nasty quirk: if all sub-1MB memory is used for boot > > - * services, we can get here without having allocated the > > - * real mode trampoline. It's too late to hand boot services > > - * memory back to the memblock allocator, so instead > > - * try to manually allocate the trampoline if needed. > > - * > > - * I've seen this on a Dell XPS 13 9350 with firmware > > - * 1.4.4 with SGX enabled booting Linux via Fedora 24's > > - * grub2-efi on a hard disk. (And no, I don't know why > > - * this happened, but Linux should still try to boot rather > > - * panicking early.) > > + * The sub-1MB memory may be within the range[0, SZ_1M] > > + * or across the low-1M memory boundary. Let's handle > > + * these two cases and hold the whole low-1M memory > > + * unconditionally. > > */ > > - rm_size = real_mode_size_needed(); > > - if (rm_size && (start + rm_size) < (1<<20) && size >= rm_size) { > > - set_real_mode_mem(start); This will restore the issue with Dell XPS described above (presuming it's still relevant with recent kernels). > > - start += rm_size; > > - size -= rm_size; > > + if (start < SZ_1M) { > > + /* Within the range[0, SZ_1M] */ > > + if (end <= SZ_1M) > > + continue; > > + else { > > + /* Across the low-1M memory boundary */ > > + size -= (SZ_1M - start); > > + start = SZ_1M; > > + } > > } > > > > memblock_free_late(start, size); > > -- > > I don't think this will be needed when this here happens: > > https://lkml.kernel.org/r/YK%2Bgv0vDfLVD7Sqp@kernel.org Right, but TBH, I didn't update efi_free_boot_services() in my initial version. I've added similar change there now and I'm waiting now to see if kbuild is happy with this: https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=x86/reservelow -- Sincerely yours, Mike.