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<h2 class="title"><a name="retpoline" id=
"retpoline"></a>Chapter 26. NVIDIA Spectre V2
Mitigation</h2>
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<p>The NVIDIA Linux driver supports the retpoline Spectre V2
mitigation technique as identified by: <a href=
"https://software.intel.com/security-software-guidance/api-app/sites/default/files/Retpoline-A-Branch-Target-Injection-Mitigation.pdf"
target=
"_top">https://software.intel.com/security-software-guidance/api-app/sites/default/files/Retpoline-A-Branch-Target-Injection-Mitigation.pdf</a></p>
<p>For Linux systems that define CONFIG_RETPOLINE or
CONFIG_MITIGATION_RETPOLINE, the NVIDIA driver yields to the
kernel's implementation of Spectre V2 mitigation. When
CONFIG_RETPOLINE or CONFIG_MITIGATION_RETPOLINE is not defined, the
NVIDIA Linux driver implements the retpoline thunk without the
Spectre V2 mitigation.</p>
<p>Linux kernels that implement retpoline based Spectre V2
mitigation provide a kernel boot flag to enable or disable the
feature. When enabled, users may notice a performance degradation.
In order to recover performance, the user can disable the feature
using the <span><strong class="command">spectre_v2</strong></span>
boot flag (unsafe).</p>
<pre class="screen">
spectre_v2=off
</pre>
<p>Please note that CONFIG_RETPOLINE has been renamed to
CONFIG_MITIGATION_RETPOLINE by commit <code class=
"computeroutput">aefb2f2e619b</code> ("x86/bugs: Rename
CONFIG_RETPOLINE => CONFIG_MITIGATION_RETPOLINE") in Linux
kernel v6.9.</p>
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