From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Borislav Petkov <bpetkov@suse.de>,
Michal Hocko <mhocko@suse.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Borislav Petkov <bp@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Ben Hutchings <ben@decadent.org.uk>
Subject: [PATCH 4.4 18/20] x86/tsx: Add config options to set tsx=on|off|auto
Date: Fri, 15 Nov 2019 14:20:47 +0800 [thread overview]
Message-ID: <20191115062015.179463426@linuxfoundation.org> (raw)
In-Reply-To: <20191115062006.854443935@linuxfoundation.org>
From: Michal Hocko <mhocko@suse.com>
commit db616173d787395787ecc93eef075fa975227b10 upstream.
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>
[bwh: Backported to 4.4: adjust doc filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/Kconfig | 45 +++++++++++++++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/tsx.c | 22 ++++++++++++++++------
2 files changed, 61 insertions(+), 6 deletions(-)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1695,6 +1695,51 @@ config X86_INTEL_MPX
If unsure, say N.
+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/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
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -73,6 +73,14 @@ static bool __init tsx_ctrl_is_supported
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))
+ return TSX_CTRL_DISABLE;
+
+ return TSX_CTRL_ENABLE;
+}
+
void __init tsx_init(void)
{
char arg[5] = {};
@@ -88,17 +96,19 @@ void __init tsx_init(void)
} else if (!strcmp(arg, "off")) {
tsx_ctrl_state = TSX_CTRL_DISABLE;
} else if (!strcmp(arg, "auto")) {
- if (boot_cpu_has_bug(X86_BUG_TAA))
- tsx_ctrl_state = TSX_CTRL_DISABLE;
- else
- tsx_ctrl_state = TSX_CTRL_ENABLE;
+ tsx_ctrl_state = x86_get_tsx_auto_mode();
} else {
tsx_ctrl_state = TSX_CTRL_DISABLE;
pr_err("tsx: invalid option, defaulting to off\n");
}
} else {
- /* tsx= not provided, defaulting to off */
- tsx_ctrl_state = TSX_CTRL_DISABLE;
+ /* tsx= not provided */
+ if (IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_AUTO))
+ tsx_ctrl_state = x86_get_tsx_auto_mode();
+ else if (IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_OFF))
+ tsx_ctrl_state = TSX_CTRL_DISABLE;
+ else
+ tsx_ctrl_state = TSX_CTRL_ENABLE;
}
if (tsx_ctrl_state == TSX_CTRL_DISABLE) {
next prev parent reply other threads:[~2019-11-15 6:21 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-15 6:20 [PATCH 4.4 00/20] 4.4.202-stable review Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 01/20] kvm: mmu: Dont read PDPTEs when paging is not enabled Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 02/20] MIPS: BCM63XX: fix switch core reset on BCM6368 Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 03/20] powerpc/Makefile: Use cflags-y/aflags-y for setting endian options Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 04/20] powerpc: Fix compiling a BE kernel with a powerpc64le toolchain Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 05/20] powerpc/boot: Request no dynamic linker for boot wrapper Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 06/20] KVM: Introduce kvm_get_arch_capabilities() Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 07/20] KVM: x86: Emulate MSR_IA32_ARCH_CAPABILITIES on AMD hosts Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 08/20] kvm: x86: IA32_ARCH_CAPABILITIES is always supported Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 09/20] KVM: x86: use Intel speculation bugs and features as derived in generic x86 code Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 10/20] x86/msr: Add the IA32_TSX_CTRL MSR Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 11/20] x86/cpu: Add a helper function x86_read_arch_cap_msr() Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 12/20] x86/cpu: Add a "tsx=" cmdline option with TSX disabled by default Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 13/20] x86/speculation/taa: Add mitigation for TSX Async Abort Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 14/20] x86/speculation/taa: Add sysfs reporting " Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 15/20] kvm/x86: Export MDS_NO=0 to guests when TSX is enabled Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 16/20] x86/tsx: Add "auto" option to the tsx= cmdline parameter Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 17/20] x86/speculation/taa: Add documentation for TSX Async Abort Greg Kroah-Hartman
2019-11-15 6:20 ` Greg Kroah-Hartman [this message]
2019-11-15 6:20 ` [PATCH 4.4 19/20] x86/speculation/taa: Fix printing of TAA_MSG_SMT on IBRS_ALL CPUs Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.4 20/20] x86/bugs: Add ITLB_MULTIHIT bug infrastructure Greg Kroah-Hartman
2019-11-15 12:20 ` [PATCH 4.4 00/20] 4.4.202-stable review kernelci.org bot
2019-11-15 13:50 ` Jon Hunter
2019-11-15 13:55 ` Guenter Roeck
2019-11-15 15:53 ` Naresh Kamboju
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