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author | Tim Chen <tim.c.chen@linux.intel.com> | 2018-11-25 19:33:46 +0100 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-05 19:32:03 +0100 |
commit | 69985a2cae82ebca281da7e7275bba7ef2b3dca8 (patch) | |
tree | a9b4580a66662bf7754fcc04c05929793653bbe7 /arch/x86/kernel/cpu | |
parent | 711875432218e9e819bfde90cb99c61569c8fa90 (diff) | |
download | linux-stable-69985a2cae82ebca281da7e7275bba7ef2b3dca8.tar.gz linux-stable-69985a2cae82ebca281da7e7275bba7ef2b3dca8.tar.bz2 linux-stable-69985a2cae82ebca281da7e7275bba7ef2b3dca8.zip |
x86/speculation: Prepare for per task indirect branch speculation control
commit 5bfbe3ad5840d941b89bcac54b821ba14f50a0ba upstream
To avoid the overhead of STIBP always on, it's necessary to allow per task
control of STIBP.
Add a new task flag TIF_SPEC_IB and evaluate it during context switch if
SMT is active and flag evaluation is enabled by the speculation control
code. Add the conditional evaluation to x86_virt_spec_ctrl() as well so the
guest/host switch works properly.
This has no effect because TIF_SPEC_IB cannot be set yet and the static key
which controls evaluation is off. Preparatory patch for adding the control
code.
[ tglx: Simplify the context switch logic and make the TIF evaluation
depend on SMP=y and on the static key controlling the conditional
update. Rename it to TIF_SPEC_IB because it controls both STIBP and
IBPB ]
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185005.176917199@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kernel/cpu')
-rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index de53f7806355..3bbd512638ac 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -148,6 +148,10 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest) static_cpu_has(X86_FEATURE_AMD_SSBD)) hostval |= ssbd_tif_to_spec_ctrl(ti->flags); + /* Conditional STIBP enabled? */ + if (static_branch_unlikely(&switch_to_cond_stibp)) + hostval |= stibp_tif_to_spec_ctrl(ti->flags); + if (hostval != guestval) { msrval = setguest ? guestval : hostval; wrmsrl(MSR_IA32_SPEC_CTRL, msrval); |