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 4.9 14/31] x86/tsx: Add config options to set tsx=on|off|auto
Date: Fri, 15 Nov 2019 14:20:43 +0800 [thread overview]
Message-ID: <20191115062015.626684228@linuxfoundation.org> (raw)
In-Reply-To: <20191115062009.813108457@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 4.9: 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
@@ -1755,6 +1755,51 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS
If unsure, say y.
+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 6:24 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-15 6:20 [PATCH 4.9 00/31] 4.9.202-stable review Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 01/31] kvm: mmu: Dont read PDPTEs when paging is not enabled Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 02/31] Bluetooth: hci_ldisc: Postpone HCI_UART_PROTO_READY bit set in hci_uart_set_proto() Greg Kroah-Hartman
2019-11-15 16:10 ` Ralph Siemsen
2019-11-16 7:56 ` Greg Kroah-Hartman
2019-11-18 20:27 ` Ralph Siemsen
2019-11-19 4:47 ` Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 03/31] MIPS: BCM63XX: fix switch core reset on BCM6368 Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 04/31] usb: gadget: core: unmap request from DMA only if previously mapped Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 05/31] KVM: x86: use Intel speculation bugs and features as derived in generic x86 code Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 06/31] x86/msr: Add the IA32_TSX_CTRL MSR Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 07/31] x86/cpu: Add a helper function x86_read_arch_cap_msr() Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 08/31] x86/cpu: Add a "tsx=" cmdline option with TSX disabled by default Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 09/31] x86/speculation/taa: Add mitigation for TSX Async Abort Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 10/31] x86/speculation/taa: Add sysfs reporting " Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 11/31] kvm/x86: Export MDS_NO=0 to guests when TSX is enabled Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 12/31] x86/tsx: Add "auto" option to the tsx= cmdline parameter Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 13/31] 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 4.9 15/31] x86/speculation/taa: Fix printing of TAA_MSG_SMT on IBRS_ALL CPUs Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 16/31] KVM: x86: simplify ept_misconfig Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 17/31] KVM: x86: extend usage of RET_MMIO_PF_* constants Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 18/31] kvm: Convert kvm_lock to a mutex Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 19/31] kvm: x86: Do not release the page inside mmu_set_spte() Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 20/31] KVM: x86: make FNAME(fetch) and __direct_map more similar Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 21/31] KVM: x86: remove now unneeded hugepage gfn adjustment Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 22/31] KVM: x86: change kvm_mmu_page_get_gfn BUG_ON to WARN_ON Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 23/31] KVM: x86: Add is_executable_pte() Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 24/31] KVM: x86: add tracepoints around __direct_map and FNAME(fetch) Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 25/31] KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is active Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 26/31] x86/bugs: Add ITLB_MULTIHIT bug infrastructure Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 27/31] cpu/speculation: Uninline and export CPU mitigations helpers Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 28/31] kvm: mmu: ITLB_MULTIHIT mitigation Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 29/31] kvm: Add helper function for creating VM worker threads Greg Kroah-Hartman
2019-11-15 6:20 ` [PATCH 4.9 30/31] kvm: x86: mmu: Recovery of shattered NX large pages Greg Kroah-Hartman
2019-11-15 6:21 ` [PATCH 4.9 31/31] Documentation: Add ITLB_MULTIHIT documentation Greg Kroah-Hartman
2019-11-15 12:00 ` [PATCH 4.9 00/31] 4.9.202-stable review kernelci.org bot
2019-11-15 13:50 ` Jon Hunter
2019-11-15 15:07 ` Greg Kroah-Hartman
2019-11-15 13:56 ` Guenter Roeck
2019-11-15 15:08 ` Greg Kroah-Hartman
2019-11-15 15:52 ` Naresh Kamboju
2019-11-16 8:02 ` Greg Kroah-Hartman
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