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authorSean Christopherson <seanjc@google.com>2024-04-20 03:05:55 +0300
committerBorislav Petkov (AMD) <bp@alien8.de>2024-04-25 16:47:39 +0300
commitce0abef6a1d540acef85068e0e82bdf1fbeeb0e9 (patch)
tree351692e7d9b06fe49aa7f6d1419cde3a7200d13d /Documentation/admin-guide
parentfe42754b94a42d08cf9501790afc25c4f6a5f631 (diff)
downloadlinux-ce0abef6a1d540acef85068e0e82bdf1fbeeb0e9.tar.xz
cpu: Ignore "mitigations" kernel parameter if CPU_MITIGATIONS=n
Explicitly disallow enabling mitigations at runtime for kernels that were built with CONFIG_CPU_MITIGATIONS=n, as some architectures may omit code entirely if mitigations are disabled at compile time. E.g. on x86, a large pile of Kconfigs are buried behind CPU_MITIGATIONS, and trying to provide sane behavior for retroactively enabling mitigations is extremely difficult, bordering on impossible. E.g. page table isolation and call depth tracking require build-time support, BHI mitigations will still be off without additional kernel parameters, etc. [ bp: Touchups. ] Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20240420000556.2645001-3-seanjc@google.com
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 902ecd92a29f..213d0719e2b7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3423,6 +3423,9 @@
arch-independent options, each of which is an
aggregation of existing arch-specific options.
+ Note, "mitigations" is supported if and only if the
+ kernel was built with CPU_MITIGATIONS=y.
+
off
Disable all optional CPU mitigations. This
improves system performance, but it may also