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Message-Id: <20190426153150.21228-16-changbin.du@gmail.com>
Date: Fri, 26 Apr 2019 23:31:38 +0800
From: Changbin Du <changbin.du@...il.com>
To: Jonathan Corbet <corbet@....net>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
mchehab+samsung@...nel.org, Changbin Du <changbin.du@...il.com>
Subject: [PATCH 15/27] Documentation: x86: convert pti.txt to reST
This converts the plain text documentation to reStructuredText format and
add it to Sphinx TOC tree. No essential content change.
Signed-off-by: Changbin Du <changbin.du@...il.com>
---
Documentation/x86/index.rst | 1 +
Documentation/x86/{pti.txt => pti.rst} | 17 +++++++++++++----
2 files changed, 14 insertions(+), 4 deletions(-)
rename Documentation/x86/{pti.txt => pti.rst} (96%)
diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index a0426ab156bd..1c675cef14d7 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -21,3 +21,4 @@ Linux x86 Support
protection-keys
intel_mpx
amd-memory-encryption
+ pti
diff --git a/Documentation/x86/pti.txt b/Documentation/x86/pti.rst
similarity index 96%
rename from Documentation/x86/pti.txt
rename to Documentation/x86/pti.rst
index 5cd58439ad2d..4b858a9bad8d 100644
--- a/Documentation/x86/pti.txt
+++ b/Documentation/x86/pti.rst
@@ -1,9 +1,15 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+Page Table Isolation (PTI)
+==========================
+
Overview
========
-Page Table Isolation (pti, previously known as KAISER[1]) is a
+Page Table Isolation (pti, previously known as KAISER [1]_) is a
countermeasure against attacks on the shared user/kernel address
-space such as the "Meltdown" approach[2].
+space such as the "Meltdown" approach [2]_.
To mitigate this class of attacks, we create an independent set of
page tables for use only when running userspace applications. When
@@ -60,6 +66,7 @@ Protection against side-channel attacks is important. But,
this protection comes at a cost:
1. Increased Memory Use
+
a. Each process now needs an order-1 PGD instead of order-0.
(Consumes an additional 4k per process).
b. The 'cpu_entry_area' structure must be 2MB in size and 2MB
@@ -68,6 +75,7 @@ this protection comes at a cost:
is decompressed, but no space in the kernel image itself.
2. Runtime Cost
+
a. CR3 manipulation to switch between the page table copies
must be done at interrupt, syscall, and exception entry
and exit (it can be skipped when the kernel is interrupted,
@@ -142,6 +150,7 @@ ideally doing all of these in parallel:
interrupted, including nested NMIs. Using "-c" boosts the rate of
NMIs, and using two -c with separate counters encourages nested NMIs
and less deterministic behavior.
+ ::
while true; do perf record -c 10000 -e instructions,cycles -a sleep 10; done
@@ -182,5 +191,5 @@ that are worth noting here.
tended to be TLB invalidation issues. Usually invalidating
the wrong PCID, or otherwise missing an invalidation.
-1. https://gruss.cc/files/kaiser.pdf
-2. https://meltdownattack.com/meltdown.pdf
+.. [1] https://gruss.cc/files/kaiser.pdf
+.. [2] https://meltdownattack.com/meltdown.pdf
--
2.20.1
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