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Subject[PATCH v4 0/4] x86/mm: Fix some issues with using trampoline_pgd
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From: Joerg Roedel <jroedel@suse.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 v3->v4:

- Rebased to latest tip/master
- Addressed Boris' review comments

Link to v3: https://lore.kernel.org/all/20211001154817.29225-1-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/include/asm/tlbflush.h | 5 +++++
arch/x86/kernel/head64.c | 2 ++
arch/x86/kernel/head_64.S | 19 ++++++++++++++++-
arch/x86/kernel/reboot.c | 12 ++---------
arch/x86/mm/init.c | 5 +++++
arch/x86/mm/tlb.c | 8 ++-----
arch/x86/realmode/init.c | 38 ++++++++++++++++++++++++++++++++-
8 files changed, 72 insertions(+), 18 deletions(-)


base-commit: b6c28e3cc445bf451a516ac075ec27b4619e4f5f
--
2.34.0

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