linux-kernel - [PATCH v3 0/4] x86/mm: Fix some issues with using trampoline

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Date:   Fri,  1 Oct 2021 17:48:13 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        hpa@...or.com, Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Joerg Roedel <jroedel@...e.de>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brijesh Singh <brijesh.singh@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/4] x86/mm: Fix some issues with using trampoline_pgd

From: Joerg Roedel <jroedel@...e.de>

Hi,

here are a couple of fixes and documentation improvements for the use
of the trampoline_pgd in the kernel. Most importantly it fixes the
issue that switching to the trampoline_pgd will unmap the kernel stack
and real_mode_header, making crashes likely before the code can
actually jump to real mode.

The first patch adds a comment to document that the trampoline_pgd
aliases kernel page-tables in the user address range, establishing
global TLB entries for these addresses. The next two patches add
global TLB flushes when switching to and from the trampoline_pgd.

The last patch extends the trampoline_pgd to cover the whole kernel
address range. This is needed to make sure the stack and the
real_mode_header are still mapped after the switch and that the code
flow can safely reach real-mode.

Please review.

Thanks,

	Joerg

Changes v2->v3:

	- Addressed review comments from Dave Hansen

Link to v2: https://lore.kernel.org/lkml/20210929145501.4612-1-joro@8bytes.org/

Joerg Roedel (4):
  x86/realmode: Add comment for Global bit usage in trampline_pgd
  x86/mm/64: Flush global TLB on boot and AP bringup
  x86/mm: Flush global TLB when switching to trampoline page-table
  x86/64/mm: Map all kernel memory into trampoline_pgd

 arch/x86/include/asm/realmode.h |  1 +
 arch/x86/kernel/head64.c        | 15 ++++++++++++++
 arch/x86/kernel/head_64.S       | 19 +++++++++++++++++-
 arch/x86/kernel/reboot.c        | 12 ++---------
 arch/x86/mm/init.c              |  5 +++++
 arch/x86/realmode/init.c        | 35 ++++++++++++++++++++++++++++++++-
 6 files changed, 75 insertions(+), 12 deletions(-)

base-commit: 5816b3e6577eaa676ceb00a848f0fd65fe2adc29
-- 
2.33.0