[tip: x86/bugs] x86/bugs: Add a separate config for L1TF

[tip-bot2 for Breno Leitao]

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     3a4ee4ff819b2bd09f1eca4a90846f2be449bd51
Gitweb:        https://git.kernel.org/tip/3a4ee4ff819b2bd09f1eca4a90846f2be449bd51
Author:        Breno Leitao <leitao@xxxxxxxxxx>
AuthorDate:    Mon, 29 Jul 2024 09:40:52 -07:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 30 Jul 2024 11:23:17 +02:00

x86/bugs: Add a separate config for L1TF

Currently, the CONFIG_SPECULATION_MITIGATIONS is halfway populated,
where some mitigations have entries in Kconfig, and they could be
modified, while others mitigations do not have Kconfig entries, and
could not be controlled at build time.

Create an entry for the L1TF CPU mitigation under
CONFIG_SPECULATION_MITIGATIONS. This allow users to enable or disable
it at compilation time.

Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240729164105.554296-5-leitao@xxxxxxxxxx
---
 arch/x86/Kconfig           | 10 ++++++++++
 arch/x86/kernel/cpu/bugs.c |  3 ++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b169677..290f086 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2682,6 +2682,16 @@ config MITIGATION_MMIO_STALE_DATA
 	  attacker to have access to MMIO.
 	  See also
 	  <file:Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst>
+
+config MITIGATION_L1TF
+	bool "Mitigate L1 Terminal Fault (L1TF) hardware bug"
+	depends on CPU_SUP_INTEL
+	default y
+	help
+	  Mitigate L1 Terminal Fault (L1TF) hardware bug. L1 Terminal Fault is a
+	  hardware vulnerability which allows unprivileged speculative access to data
+	  available in the Level 1 Data Cache.
+	  See <file:Documentation/admin-guide/hw-vuln/l1tf.rst
 endif
 
 config ARCH_HAS_ADD_PAGES
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9b0d058..4fde9bd 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2374,7 +2374,8 @@ EXPORT_SYMBOL_GPL(itlb_multihit_kvm_mitigation);
 #define pr_fmt(fmt)	"L1TF: " fmt
 
 /* Default mitigation for L1TF-affected CPUs */
-enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH;
+enum l1tf_mitigations l1tf_mitigation __ro_after_init =
+	IS_ENABLED(CONFIG_MITIGATION_L1TF) ? L1TF_MITIGATION_FLUSH : L1TF_MITIGATION_OFF;
 #if IS_ENABLED(CONFIG_KVM_INTEL)
 EXPORT_SYMBOL_GPL(l1tf_mitigation);
 #endif