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x86/tsx: Add a feature bit for TSX control MSR support

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commit aaa65d17ee 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@citrix.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/de619764e1d98afbb7a5fa58424f1278ede37b45.1668539735.git.pawan.kumar.gupta@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pawan Gupta 2022-11-15 11:17:05 -08:00 • committed by Justin Hammond
parent ec2035c8e3
commit 185557265f
2 changed files with 20 additions and 21 deletions
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3
arch/x86/include/asm/cpufeatures.h
View file

@ -303,6 +303,9 @@
#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 */

38
arch/x86/kernel/cpu/tsx.c
View file

@ -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;
}