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authorJosh Poimboeuf <jpoimboe@kernel.org>2024-04-10 22:40:45 -0700
committerIngo Molnar <mingo@kernel.org>2024-04-11 10:30:25 +0200
commitdfe648903f42296866d79f10d03f8c85c9dfba30 (patch)
treeb5bf6330b376cdc73dee8daf5198de3c1be9d50e /Documentation
parentf337a6a21e2fd67eadea471e93d05dd37baaa9be (diff)
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x86/bugs: Fix BHI documentation
Fix up some inaccuracies in the BHI documentation. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/8c84f7451bfe0dd08543c6082a383f390d4aa7e2.1712813475.git.jpoimboe@kernel.org
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/hw-vuln/spectre.rst15
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt12
2 files changed, 15 insertions, 12 deletions
diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index b70b1d8bd8e6..3cf18e4a1d9a 100644
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -439,11 +439,11 @@ The possible values in this file are:
- System is protected by retpoline
* - BHI: BHI_DIS_S
- System is protected by BHI_DIS_S
- * - BHI: SW loop; KVM SW loop
+ * - BHI: SW loop, KVM SW loop
- System is protected by software clearing sequence
* - BHI: Syscall hardening
- Syscalls are hardened against BHI
- * - BHI: Syscall hardening; KVM: SW loop
+ * - BHI: Syscall hardening, KVM: SW loop
- System is protected from userspace attacks by syscall hardening; KVM is protected by software clearing sequence
Full mitigation might require a microcode update from the CPU
@@ -666,13 +666,14 @@ kernel command line.
of the HW BHI control and the SW BHB clearing sequence.
on
- unconditionally enable.
+ (default) Enable the HW or SW mitigation as
+ needed.
off
- unconditionally disable.
+ Disable the mitigation.
auto
- enable if hardware mitigation
- control(BHI_DIS_S) is available, otherwise
- enable alternate mitigation in KVM.
+ Enable the HW mitigation if needed, but
+ *don't* enable the SW mitigation except for KVM.
+ The system may be vulnerable.
For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 70046a019d42..a029ad6c4963 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3444,6 +3444,7 @@
retbleed=off [X86]
spec_rstack_overflow=off [X86]
spec_store_bypass_disable=off [X86,PPC]
+ spectre_bhi=off [X86]
spectre_v2_user=off [X86]
srbds=off [X86,INTEL]
ssbd=force-off [ARM64]
@@ -6069,11 +6070,12 @@
deployment of the HW BHI control and the SW BHB
clearing sequence.
- on - unconditionally enable.
- off - unconditionally disable.
- auto - (default) enable hardware mitigation
- (BHI_DIS_S) if available, otherwise enable
- alternate mitigation in KVM.
+ on - (default) Enable the HW or SW mitigation
+ as needed.
+ off - Disable the mitigation.
+ auto - Enable the HW mitigation if needed, but
+ *don't* enable the SW mitigation except
+ for KVM. The system may be vulnerable.
spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2
(indirect branch speculation) vulnerability.