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authorMichal Hocko <mhocko@suse.com>2019-10-23 13:35:50 +0300
committerThomas Gleixner <tglx@linutronix.de>2019-10-28 11:12:18 +0300
commitdb616173d787395787ecc93eef075fa975227b10 (patch)
tree9b55a074699594c3d20d2c1959d89a111717b908 /arch/x86/Kconfig
parenta7a248c593e4fd7a67c50b5f5318fe42a0db335e (diff)
downloadlinux-db616173d787395787ecc93eef075fa975227b10.tar.xz
x86/tsx: Add config options to set tsx=on|off|auto
There is a general consensus that TSX usage is not largely spread while the history shows there is a non trivial space for side channel attacks possible. Therefore the tsx is disabled by default even on platforms that might have a safe implementation of TSX according to the current knowledge. This is a fair trade off to make. There are, however, workloads that really do benefit from using TSX and updating to a newer kernel with TSX disabled might introduce a noticeable regressions. This would be especially a problem for Linux distributions which will provide TAA mitigations. Introduce config options X86_INTEL_TSX_MODE_OFF, X86_INTEL_TSX_MODE_ON and X86_INTEL_TSX_MODE_AUTO to control the TSX feature. The config setting can be overridden by the tsx cmdline options. [ bp: Text cleanups from Josh. ] Suggested-by: Borislav Petkov <bpetkov@suse.de> Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Diffstat (limited to 'arch/x86/Kconfig')
-rw-r--r--arch/x86/Kconfig45
1 files changed, 45 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d6e1faa28c58..8ef85139553f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1940,6 +1940,51 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS
If unsure, say y.
+choice
+ prompt "TSX enable mode"
+ depends on CPU_SUP_INTEL
+ default X86_INTEL_TSX_MODE_OFF
+ help
+ Intel's TSX (Transactional Synchronization Extensions) feature
+ allows to optimize locking protocols through lock elision which
+ can lead to a noticeable performance boost.
+
+ On the other hand it has been shown that TSX can be exploited
+ to form side channel attacks (e.g. TAA) and chances are there
+ will be more of those attacks discovered in the future.
+
+ Therefore TSX is not enabled by default (aka tsx=off). An admin
+ might override this decision by tsx=on the command line parameter.
+ Even with TSX enabled, the kernel will attempt to enable the best
+ possible TAA mitigation setting depending on the microcode available
+ for the particular machine.
+
+ This option allows to set the default tsx mode between tsx=on, =off
+ and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
+ details.
+
+ Say off if not sure, auto if TSX is in use but it should be used on safe
+ platforms or on if TSX is in use and the security aspect of tsx is not
+ relevant.
+
+config X86_INTEL_TSX_MODE_OFF
+ bool "off"
+ help
+ TSX is disabled if possible - equals to tsx=off command line parameter.
+
+config X86_INTEL_TSX_MODE_ON
+ bool "on"
+ help
+ TSX is always enabled on TSX capable HW - equals the tsx=on command
+ line parameter.
+
+config X86_INTEL_TSX_MODE_AUTO
+ bool "auto"
+ help
+ TSX is enabled on TSX capable HW that is believed to be safe against
+ side channel attacks- equals the tsx=auto command line parameter.
+endchoice
+
config EFI
bool "EFI runtime service support"
depends on ACPI