linux-kernel - [PATCH 0/2] x86/xen: avoid 32-bit writes to PTEs in PV PAE guests

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Message-Id: <20180820051456.20779-1-jgross@suse.com>
Date:   Mon, 20 Aug 2018 07:14:54 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org
Cc:     boris.ostrovsky@...cle.com, hpa@...or.com, tglx@...utronix.de,
        mingo@...hat.com, Juergen Gross <jgross@...e.com>
Subject: [PATCH 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
hypercalls.

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 | 14 ++++++++------
 arch/x86/xen/mmu_pv.c                 |  7 +++----
 2 files changed, 11 insertions(+), 10 deletions(-)

-- 
2.13.7