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authorChangbin Du <changbin.du@gmail.com>2019-05-08 15:21:29 (GMT)
committerJonathan Corbet <corbet@lwn.net>2019-05-08 20:34:10 (GMT)
commitea0765e835e084707abb7e14d84b572f5ffe4242 (patch)
treeefff70d7e4b6a449476508d3233d9a9802034cb9 /Documentation/x86
parent0c7180f2e4e6fc02f268e18c4f753d9f9cdfb5ad (diff)
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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@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/x86')
-rw-r--r--Documentation/x86/index.rst1
-rw-r--r--Documentation/x86/pti.rst (renamed from Documentation/x86/pti.txt)17
2 files changed, 14 insertions, 4 deletions
diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index 85f1f44..6719def 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -21,3 +21,4 @@ x86-specific Documentation
protection-keys
intel_mpx
amd-memory-encryption
+ pti
diff --git a/Documentation/x86/pti.txt b/Documentation/x86/pti.rst
index 5cd5843..4b858a9 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