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Date: Wed, 7 Apr 2021 07:50:23 -0500
From: Ramakrishna Saripalli <rsaripal@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
Jonathan Corbet <corbet@....net>
CC: <rsaripal@....com>
Subject: [PATCH 5/5] x86/speculation: Add PSF mitigation kernel parameters
From: Ramakrishna Saripalli <rk.saripalli@....com>
PSF mitigation introduces new kernel parameters.
The kernel parameters for PSF mitigation are modeled
after spec_store_bypass_disable.
Signed-off-by: Ramakrishna Saripalli<rk.saripalli@....com>
---
.../admin-guide/kernel-parameters.txt | 45 +++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04545725f187..68dfde77a87d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2876,6 +2876,7 @@
nospectre_v2 [X86,PPC,S390,ARM64]
spectre_v2_user=off [X86]
spec_store_bypass_disable=off [X86,PPC]
+ psfd=off [X86]
ssbd=force-off [ARM64]
l1tf=off [X86]
mds=off [X86]
@@ -3243,6 +3244,8 @@
nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
+ nopsfd [HW,X86] Disable mitigation for Predictive Store Forwarding.
+
nosmt [KNL,S390] Disable symmetric multithreading (SMT).
Equivalent to smt=1.
@@ -4002,6 +4005,48 @@
that).
Format: <bool>
+ psfd= [HW,X86]
+ Predictive Store Forwarding Disable control
+
+ Certain AMD processors feature a new technology called Predictive
+ Store Forwarding. This feature is designed to improve the
+ performance of code execution by predicting dependencies
+ between loads and stores.
+
+ Modern processors implement techniques to optimize the
+ execution of a load instruction to an address that was
+ recently written by a store instruction.
+
+ PSF expands on the above by speculating on the relationship
+ between loads and stores without waiting for address
+ calculation to complete. With PSF, CPU learns over time the
+ relationship between loads and stores.
+
+ Incorrect PSF predictions can occur for various reasons.
+ Please see the AMD PSF whitepaper for more information.
+
+ All AMD processors that implement PSF also provide ability
+ to control mitigation of PSF.
+
+ Following options are provided to control PSF mitigation.
+
+ The options are:
+ on - Unconditionally disable Speculative Store Bypass
+ off - Unconditionally enable Speculative Store Bypass
+ auto - Kernel detects whether the CPU is vulnerable.
+ If the CPU is not vulnerable, off is selected.
+ If the CPU is vulnerable, default mitigation is
+ KConfig dependent.
+ prctl - Control Predictive Store Forwarding per thread
+ via prctl. Predictive Store Forwarding is enabled
+ per process by default. The state of the control
+ is inherited on fork.
+ seccomp - Same as prctl above but all seccomp threads will
+ disable PSF unless they opt out.
+
+ Default mitigations:
+ [X86] If CONFIG_SECCOMP=y "seccomp" else "prctl"
+
psi= [KNL] Enable or disable pressure stall information
tracking.
Format: <bool>
--
2.25.1
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