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| 1 | +x86/bugs: Fix BHI documentation |
| 2 | + |
| 3 | +jira LE-2015 |
| 4 | +cve CVE-2024-2201 |
| 5 | +Rebuild_History Non-Buildable kernel-5.14.0-427.42.1.el9_4 |
| 6 | +commit-author Josh Poimboeuf <jpoimboe@kernel.org> |
| 7 | +commit dfe648903f42296866d79f10d03f8c85c9dfba30 |
| 8 | +Empty-Commit: Cherry-Pick Conflicts during history rebuild. |
| 9 | +Will be included in final tarball splat. Ref for failed cherry-pick at: |
| 10 | +ciq/ciq_backports/kernel-5.14.0-427.42.1.el9_4/dfe64890.failed |
| 11 | + |
| 12 | +Fix up some inaccuracies in the BHI documentation. |
| 13 | + |
| 14 | +Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") |
| 15 | + Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> |
| 16 | + Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| 17 | + Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> |
| 18 | + Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| 19 | + Cc: Sean Christopherson <seanjc@google.com> |
| 20 | +Link: https://lore.kernel.org/r/8c84f7451bfe0dd08543c6082a383f390d4aa7e2.1712813475.git.jpoimboe@kernel.org |
| 21 | +(cherry picked from commit dfe648903f42296866d79f10d03f8c85c9dfba30) |
| 22 | + Signed-off-by: Jonathan Maple <jmaple@ciq.com> |
| 23 | + |
| 24 | +# Conflicts: |
| 25 | +# Documentation/admin-guide/hw-vuln/spectre.rst |
| 26 | +# Documentation/admin-guide/kernel-parameters.txt |
| 27 | +diff --cc Documentation/admin-guide/hw-vuln/spectre.rst |
| 28 | +index 166facdabe9f,3cf18e4a1d9a..000000000000 |
| 29 | +--- a/Documentation/admin-guide/hw-vuln/spectre.rst |
| 30 | ++++ b/Documentation/admin-guide/hw-vuln/spectre.rst |
| 31 | +@@@ -430,6 -429,23 +430,26 @@@ The possible values in this file are |
| 32 | + 'PBRSB-eIBRS: Not affected' CPU is not affected by PBRSB |
| 33 | + =========================== ======================================================= |
| 34 | + |
| 35 | +++<<<<<<< HEAD |
| 36 | +++======= |
| 37 | ++ - Branch History Injection (BHI) protection status: |
| 38 | ++ |
| 39 | ++ .. list-table:: |
| 40 | ++ |
| 41 | ++ * - BHI: Not affected |
| 42 | ++ - System is not affected |
| 43 | ++ * - BHI: Retpoline |
| 44 | ++ - System is protected by retpoline |
| 45 | ++ * - BHI: BHI_DIS_S |
| 46 | ++ - System is protected by BHI_DIS_S |
| 47 | ++ * - BHI: SW loop, KVM SW loop |
| 48 | ++ - System is protected by software clearing sequence |
| 49 | ++ * - BHI: Syscall hardening |
| 50 | ++ - Syscalls are hardened against BHI |
| 51 | ++ * - BHI: Syscall hardening, KVM: SW loop |
| 52 | ++ - System is protected from userspace attacks by syscall hardening; KVM is protected by software clearing sequence |
| 53 | ++ |
| 54 | +++>>>>>>> dfe648903f42 (x86/bugs: Fix BHI documentation) |
| 55 | + Full mitigation might require a microcode update from the CPU |
| 56 | + vendor. When the necessary microcode is not available, the kernel will |
| 57 | + report vulnerability. |
| 58 | +@@@ -638,6 -658,23 +658,26 @@@ kernel command line |
| 59 | + spectre_v2=off. Spectre variant 1 mitigations |
| 60 | + cannot be disabled. |
| 61 | + |
| 62 | +++<<<<<<< HEAD |
| 63 | +++======= |
| 64 | ++ spectre_bhi= |
| 65 | ++ |
| 66 | ++ [X86] Control mitigation of Branch History Injection |
| 67 | ++ (BHI) vulnerability. Syscalls are hardened against BHI |
| 68 | ++ regardless of this setting. This setting affects the deployment |
| 69 | ++ of the HW BHI control and the SW BHB clearing sequence. |
| 70 | ++ |
| 71 | ++ on |
| 72 | ++ (default) Enable the HW or SW mitigation as |
| 73 | ++ needed. |
| 74 | ++ off |
| 75 | ++ Disable the mitigation. |
| 76 | ++ auto |
| 77 | ++ Enable the HW mitigation if needed, but |
| 78 | ++ *don't* enable the SW mitigation except for KVM. |
| 79 | ++ The system may be vulnerable. |
| 80 | ++ |
| 81 | +++>>>>>>> dfe648903f42 (x86/bugs: Fix BHI documentation) |
| 82 | + For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt |
| 83 | + |
| 84 | + Mitigation selection guide |
| 85 | +diff --cc Documentation/admin-guide/kernel-parameters.txt |
| 86 | +index f74f25f00a14,a029ad6c4963..000000000000 |
| 87 | +--- a/Documentation/admin-guide/kernel-parameters.txt |
| 88 | ++++ b/Documentation/admin-guide/kernel-parameters.txt |
| 89 | +@@@ -5722,7 -6064,20 +5723,24 @@@ |
| 90 | + sonypi.*= [HW] Sony Programmable I/O Control Device driver |
| 91 | + See Documentation/admin-guide/laptops/sonypi.rst |
| 92 | + |
| 93 | +++<<<<<<< HEAD |
| 94 | + + spectre_v2= [X86] Control mitigation of Spectre variant 2 |
| 95 | +++======= |
| 96 | ++ spectre_bhi= [X86] Control mitigation of Branch History Injection |
| 97 | ++ (BHI) vulnerability. Syscalls are hardened against BHI |
| 98 | ++ reglardless of this setting. This setting affects the |
| 99 | ++ deployment of the HW BHI control and the SW BHB |
| 100 | ++ clearing sequence. |
| 101 | ++ |
| 102 | ++ on - (default) Enable the HW or SW mitigation |
| 103 | ++ as needed. |
| 104 | ++ off - Disable the mitigation. |
| 105 | ++ auto - Enable the HW mitigation if needed, but |
| 106 | ++ *don't* enable the SW mitigation except |
| 107 | ++ for KVM. The system may be vulnerable. |
| 108 | ++ |
| 109 | ++ spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2 |
| 110 | +++>>>>>>> dfe648903f42 (x86/bugs: Fix BHI documentation) |
| 111 | + (indirect branch speculation) vulnerability. |
| 112 | + The default operation protects the kernel from |
| 113 | + user space attacks. |
| 114 | +* Unmerged path Documentation/admin-guide/hw-vuln/spectre.rst |
| 115 | +* Unmerged path Documentation/admin-guide/kernel-parameters.txt |
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