This is a note to let you know that I've just added the patch titled
x86/tsx: Add a feature bit for TSX control MSR support
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-tsx-add-a-feature-bit-for-tsx-control-msr-support.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From aaa65d17eec372c6a9756833f3964ba05b05ea14 Mon Sep 17 00:00:00 2001
From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Date: Tue, 15 Nov 2022 11:17:05 -0800
Subject: x86/tsx: Add a feature bit for TSX control MSR support
From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
commit aaa65d17eec372c6a9756833f3964ba05b05ea14 upstream.
Support for the TSX control MSR is enumerated in MSR_IA32_ARCH_CAPABILITIES.
This is different from how other CPU features are enumerated i.e. via
CPUID. Currently, a call to tsx_ctrl_is_supported() is required for
enumerating the feature. In the absence of a feature bit for TSX control,
any code that relies on checking feature bits directly will not work.
In preparation for adding a feature bit check in MSR save/restore
during suspend/resume, set a new feature bit X86_FEATURE_TSX_CTRL when
MSR_IA32_TSX_CTRL is present. Also make tsx_ctrl_is_supported() use the
new feature bit to avoid any overhead of reading the MSR.
[ bp: Remove tsx_ctrl_is_supported(), add room for two more feature
bits in word 11 which are coming up in the next merge window. ]
Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Link: https://lore.kernel.org/r/de619764e1d98afbb7a5fa58424f1278ede37b45.1668539735.git.pawan.kumar.gupta@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/cpufeatures.h | 3 ++
arch/x86/kernel/cpu/tsx.c | 38 ++++++++++++++++---------------------
2 files changed, 20 insertions(+), 21 deletions(-)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -305,6 +305,9 @@
#define X86_FEATURE_USE_IBPB_FW (11*32+16) /* "" Use IBPB during runtime firmware calls */
#define X86_FEATURE_RSB_VMEXIT_LITE (11*32+17) /* "" Fill RSB on VM exit when EIBRS is enabled */
+
+#define X86_FEATURE_MSR_TSX_CTRL (11*32+20) /* "" MSR IA32_TSX_CTRL (Intel) implemented */
+
/* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
#define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */
#define X86_FEATURE_AVX512_BF16 (12*32+ 5) /* AVX512 BFLOAT16 instructions */
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -58,24 +58,6 @@ static void tsx_enable(void)
wrmsrl(MSR_IA32_TSX_CTRL, tsx);
}
-static bool tsx_ctrl_is_supported(void)
-{
- u64 ia32_cap = x86_read_arch_cap_msr();
-
- /*
- * TSX is controlled via MSR_IA32_TSX_CTRL. However, support for this
- * MSR is enumerated by ARCH_CAP_TSX_MSR bit in MSR_IA32_ARCH_CAPABILITIES.
- *
- * TSX control (aka MSR_IA32_TSX_CTRL) is only available after a
- * microcode update on CPUs that have their MSR_IA32_ARCH_CAPABILITIES
- * bit MDS_NO=1. CPUs with MDS_NO=0 are not planned to get
- * MSR_IA32_TSX_CTRL support even after a microcode update. Thus,
- * tsx= cmdline requests will do nothing on CPUs without
- * MSR_IA32_TSX_CTRL support.
- */
- return !!(ia32_cap & ARCH_CAP_TSX_CTRL_MSR);
-}
-
static enum tsx_ctrl_states x86_get_tsx_auto_mode(void)
{
if (boot_cpu_has_bug(X86_BUG_TAA))
@@ -135,7 +117,7 @@ static void tsx_clear_cpuid(void)
rdmsrl(MSR_TSX_FORCE_ABORT, msr);
msr |= MSR_TFA_TSX_CPUID_CLEAR;
wrmsrl(MSR_TSX_FORCE_ABORT, msr);
- } else if (tsx_ctrl_is_supported()) {
+ } else if (cpu_feature_enabled(X86_FEATURE_MSR_TSX_CTRL)) {
rdmsrl(MSR_IA32_TSX_CTRL, msr);
msr |= TSX_CTRL_CPUID_CLEAR;
wrmsrl(MSR_IA32_TSX_CTRL, msr);
@@ -158,7 +140,8 @@ static void tsx_dev_mode_disable(void)
u64 mcu_opt_ctrl;
/* Check if RTM_ALLOW exists */
- if (!boot_cpu_has_bug(X86_BUG_TAA) || !tsx_ctrl_is_supported() ||
+ if (!boot_cpu_has_bug(X86_BUG_TAA) ||
+ !cpu_feature_enabled(X86_FEATURE_MSR_TSX_CTRL) ||
!cpu_feature_enabled(X86_FEATURE_SRBDS_CTRL))
return;
@@ -191,7 +174,20 @@ void __init tsx_init(void)
return;
}
- if (!tsx_ctrl_is_supported()) {
+ /*
+ * TSX is controlled via MSR_IA32_TSX_CTRL. However, support for this
+ * MSR is enumerated by ARCH_CAP_TSX_MSR bit in MSR_IA32_ARCH_CAPABILITIES.
+ *
+ * TSX control (aka MSR_IA32_TSX_CTRL) is only available after a
+ * microcode update on CPUs that have their MSR_IA32_ARCH_CAPABILITIES
+ * bit MDS_NO=1. CPUs with MDS_NO=0 are not planned to get
+ * MSR_IA32_TSX_CTRL support even after a microcode update. Thus,
+ * tsx= cmdline requests will do nothing on CPUs without
+ * MSR_IA32_TSX_CTRL support.
+ */
+ if (x86_read_arch_cap_msr() & ARCH_CAP_TSX_CTRL_MSR) {
+ setup_force_cpu_cap(X86_FEATURE_MSR_TSX_CTRL);
+ } else {
tsx_ctrl_state = TSX_CTRL_NOT_SUPPORTED;
return;
}
Patches currently in stable-queue which might be from pawan.kumar.gupta@xxxxxxxxxxxxxxx are
queue-6.0/x86-pm-add-enumeration-check-before-spec-msrs-save-restore-setup.patch
queue-6.0/x86-tsx-add-a-feature-bit-for-tsx-control-msr-support.patch
