diff options
| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2024-03-11 16:57:09 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-04-08 19:27:06 +0200 |
| commit | 95a6ccbdc7199a14b71ad8901cb788ba7fb5167b (patch) | |
| tree | 2756d1354b90ff94be54ba551fbe6570365d2bf7 /Documentation/admin-guide | |
| parent | x86/bhi: Add BHI mitigation knob (diff) | |
| download | linux-95a6ccbdc7199a14b71ad8901cb788ba7fb5167b.tar.xz linux-95a6ccbdc7199a14b71ad8901cb788ba7fb5167b.zip | |
x86/bhi: Mitigate KVM by default
BHI mitigation mode spectre_bhi=auto does not deploy the software
mitigation by default. In a cloud environment, it is a likely scenario
where userspace is trusted but the guests are not trusted. Deploying
system wide mitigation in such cases is not desirable.
Update the auto mode to unconditionally mitigate against malicious
guests. Deploy the software sequence at VMexit in auto mode also, when
hardware mitigation is not available. Unlike the force =on mode,
software sequence is not deployed at syscalls in auto mode.
Suggested-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/spectre.rst | 7 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 5 |
2 files changed, 8 insertions, 4 deletions
diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst index 7cb99b09827c..b70b1d8bd8e6 100644 --- a/Documentation/admin-guide/hw-vuln/spectre.rst +++ b/Documentation/admin-guide/hw-vuln/spectre.rst @@ -439,10 +439,12 @@ 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 + * - 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 + - 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 vendor. When the necessary microcode is not available, the kernel will @@ -669,7 +671,8 @@ kernel command line. unconditionally disable. auto enable if hardware mitigation - control(BHI_DIS_S) is available. + control(BHI_DIS_S) is available, otherwise + enable alternate mitigation in KVM. 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 2dbe60c1db22..4fa46302f436 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6071,8 +6071,9 @@ on - unconditionally enable. off - unconditionally disable. - auto - (default) enable only if hardware mitigation - control(BHI_DIS_S) is available. + auto - (default) enable hardware mitigation + (BHI_DIS_S) if available, otherwise enable + alternate mitigation in KVM. spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2 (indirect branch speculation) vulnerability. |