x86/bugs: Add a separate config for TAA

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 TAA CPU mitigation under
CONFIG_SPECULATION_MITIGATIONS. This allow users to enable or disable
it at compilation time.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20240729164105.554296-3-leitao@debian.org

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 36e871ab1ef94d1d7d271046aeb9d9aa8d38617f..712a4f8cb7dd05ba7df41a190e163e4ca05a318b 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2659,6 +2659,17 @@ config MITIGATION_MDS
          a hardware vulnerability which allows unprivileged speculative access
          to data which is available in various CPU internal buffers.
          See also <file:Documentation/admin-guide/hw-vuln/mds.rst>
+
+config MITIGATION_TAA
+       bool "Mitigate TSX Asynchronous Abort (TAA) hardware bug"
+       depends on CPU_SUP_INTEL
+       default y
+       help
+         Enable mitigation for TSX Asynchronous Abort (TAA). TAA is a hardware
+         vulnerability that allows unprivileged speculative access to data
+         which is available in various CPU internal buffers by using
+         asynchronous aborts within an Intel TSX transactional region.
+         See also <file:Documentation/admin-guide/hw-vuln/tsx_async_abort.rst>
 endif
 
 config ARCH_HAS_ADD_PAGES

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index dbfc7d5c5f48d475b58b63a651a66bdeccaabaaa..ab306986762dd500cbd03082055702f52a934967 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -294,7 +294,8 @@ enum taa_mitigations {
 };
 
 /* Default mitigation for TAA-affected CPUs */
-static enum taa_mitigations taa_mitigation __ro_after_init = TAA_MITIGATION_VERW;
+static enum taa_mitigations taa_mitigation __ro_after_init =
+       IS_ENABLED(CONFIG_MITIGATION_TAA) ? TAA_MITIGATION_VERW : TAA_MITIGATION_OFF;
 static bool taa_nosmt __ro_after_init;
 
 static const char * const taa_strings[] = {