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Date:   Tue, 21 Aug 2018 17:37:53 +0200
From:   Juergen Gross <>
Cc:,,,, Juergen Gross <>
Subject: [PATCH v2 0/2] x86/xen: avoid 32-bit writes to PTEs in PV PAE guests

While the hypervisor emulates plain writes to PTEs happily, this is
much slower than issuing a hypercall for PTE modifcations. And writing
a PTE via two 32-bit write instructions (especially when clearing the
PTE) will result in an intermediate L1TF vulnerable PTE.

Writes to PAE PTEs should always be done with 64-bit writes or via

Juergen Gross (2):
  x86/xen: don't write ptes directly in 32-bit PV guests
  x86/pae: use 64 bit atomic xchg function in native_ptep_get_and_clear

 arch/x86/include/asm/pgtable-3level.h | 7 +++----
 arch/x86/xen/mmu_pv.c                 | 7 +++----
 2 files changed, 6 insertions(+), 8 deletions(-)


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