linux-kernel - [PATCH v3 0/2] x86: SME: Kexec/kdump memory loading fix

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Message-ID: <cover.1560969363.git.thomas.lendacky@amd.com>
Date:   Wed, 19 Jun 2019 18:40:55 +0000
From:   "Lendacky, Thomas" <Thomas.Lendacky@....com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Lianbo Jiang <lijiang@...hat.com>, Baoquan He <bhe@...hat.com>
Subject: [PATCH v3 0/2] x86: SME: Kexec/kdump memory loading fix

This series addresses an issue related to kexec/kdump when SME is active.
The SME support uses a workarea located after the end of the kernel to
perform "in-place" encryption of the kernel. When kexec/kdump is used, it
is possible that some other data used by kexec/kdump could be in this area
of memory which would cause the kexec/kdump of the kernel to fail.

Create a workarea section for use by SME in vmlinux.lds.S that is
positioned after "_end", so that the memory it occupies will be reclaimed
after its use during boot. Since it is part of the kernel image, there is
no worry now that kexec/kdump will place data in the SME workarea when
installing the kexec/kdump kernel. As part of this fix, clarify what
occupied kernel memory is reserved and what parts of the kernel memory are
discarded.

The following patches are included:
- Identify and document what parts of the kernel image are reserved
  (saved) and what is discarded.
- Create a new section that lives outside of the kernel proper, so that it
  will be reclaimed as available memory during boot, thus allowing it to
  be used as a workarea by SME for kernel in-place encryption during early
  boot..

This patch series is based on tip/master.

---

Changes from v2:
- Grammar fixes
- A more generic naming of the scratch/workarea section to indicate it
  is not restricted to SME usage

Changes from v1:
- Clarify how and where the kernel sections/memory is reserved.
- Add an explicit symbol, __end_of_kernel_reserve, for reserving the
  kernel memory rather than using __bss_stop.

Tom Lendacky (2):
  x86/mm: Identify the end of the kernel area to be reserved
  x86/mm: Create a workarea in the kernel for SME early encryption

 arch/x86/include/asm/sections.h    |  2 ++
 arch/x86/kernel/setup.c            |  8 ++++++-
 arch/x86/kernel/vmlinux.lds.S      | 34 +++++++++++++++++++++++++++++-
 arch/x86/mm/mem_encrypt_identity.c | 22 +++++++++++++++++--
 4 files changed, 62 insertions(+), 4 deletions(-)

-- 
2.17.1