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x86/speculation: Prepare arch_smt_update() for PRCTL mode 

The upcoming fine grained per task STIBP control needs to be updated on CPU
hotplug as well.

Split out the code which controls the strict mode so the prctl control code
can be added later. Mark the SMP function call argument __unused while at it.

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: Tim Chen <tim.c.chen@linux.intel.com>
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/20181125185005.759457117@linutronix.de
This commit is contained in:
Thomas Gleixner 2018-11-25 19:33:52 +01:00
parent 6d991ba509
commit 6893a959d7
1 changed files with 27 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
arch/x86/kernel/cpu/bugs.c
View File

@ -530,40 +530,44 @@ static void __init spectre_v2_select_mitigation(void)
arch_smt_update(); arch_smt_update();
} }
static bool stibp_needed(void) static void update_stibp_msr(void * __unused)
{
/* Enhanced IBRS makes using STIBP unnecessary. */
if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
return false;
/* Check for strict user mitigation mode */
return spectre_v2_user == SPECTRE_V2_USER_STRICT;
}
static void update_stibp_msr(void *info)
{ {
wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
} }
/* Update x86_spec_ctrl_base in case SMT state changed. */
static void update_stibp_strict(void)
{
u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP;
if (sched_smt_active())
mask |= SPEC_CTRL_STIBP;
if (mask == x86_spec_ctrl_base)
return;
pr_info("Update user space SMT mitigation: STIBP %s\n",
mask & SPEC_CTRL_STIBP ? "always-on" : "off");
x86_spec_ctrl_base = mask;
on_each_cpu(update_stibp_msr, NULL, 1);
}
void arch_smt_update(void) void arch_smt_update(void)
{ {
u64 mask; /* Enhanced IBRS implies STIBP. No update required. */
if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
if (!stibp_needed())
return; return;
mutex_lock(&spec_ctrl_mutex); mutex_lock(&spec_ctrl_mutex);
mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP; switch (spectre_v2_user) {
if (sched_smt_active()) case SPECTRE_V2_USER_NONE:
mask |= SPEC_CTRL_STIBP; break;
case SPECTRE_V2_USER_STRICT:
if (mask != x86_spec_ctrl_base) { update_stibp_strict();
pr_info("Spectre v2 cross-process SMT mitigation: %s STIBP\n", break;
mask & SPEC_CTRL_STIBP ? "Enabling" : "Disabling");
x86_spec_ctrl_base = mask;
on_each_cpu(update_stibp_msr, NULL, 1);
} }
mutex_unlock(&spec_ctrl_mutex); mutex_unlock(&spec_ctrl_mutex);
} }