|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.7] x86/idle: Clear SPEC_CTRL while idle
commit 68420b47d9b813ca48891b604fab379d40aa594e
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Feb 14 11:45:01 2018 +0100
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Feb 14 11:45:01 2018 +0100
x86/idle: Clear SPEC_CTRL while idle
On contemporary hardware, setting IBRS/STIBP has a performance impact on
adjacent hyperthreads. It is therefore recommended to clear the setting
before becoming idle, to avoid an idle core preventing adjacent userspace
execution from running at full performance.
Care must be taken to ensure there are no ret or indirect branch
instructions
between spec_ctrl_{enter,exit}_idle() invocations, which are forced always
inline. Care must also be taken to avoid using spec_ctrl_enter_idle()
between
flushing caches and becoming idle, in cases where that matters.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
master commit: 4c7e478d597b0346eef3a256cfd6794ac778b608
master date: 2018-01-26 14:10:21 +0000
---
xen/arch/x86/acpi/cpu_idle.c | 21 +++++++++++++++++++++
xen/arch/x86/cpu/mwait-idle.c | 7 +++++++
xen/arch/x86/domain.c | 8 ++++++++
xen/include/asm-x86/spec_ctrl.h | 34 ++++++++++++++++++++++++++++++++++
4 files changed, 70 insertions(+)
diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index a381c68..7b20945 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -56,6 +56,7 @@
#include <asm/mwait.h>
#include <xen/notifier.h>
#include <xen/cpu.h>
+#include <asm/spec_ctrl.h>
/*#define DEBUG_PM_CX*/
@@ -396,8 +397,14 @@ void mwait_idle_with_hints(unsigned int eax, unsigned int
ecx)
*/
if ( (expires > NOW() || expires == 0) && !softirq_pending(cpu) )
{
+ struct cpu_info *info = get_cpu_info();
+
cpumask_set_cpu(cpu, &cpuidle_mwait_flags);
+
+ spec_ctrl_enter_idle(info);
__mwait(eax, ecx);
+ spec_ctrl_exit_idle(info);
+
cpumask_clear_cpu(cpu, &cpuidle_mwait_flags);
}
@@ -412,6 +419,8 @@ static void acpi_processor_ffh_cstate_enter(struct
acpi_processor_cx *cx)
static void acpi_idle_do_entry(struct acpi_processor_cx *cx)
{
+ struct cpu_info *info = get_cpu_info();
+
switch ( cx->entry_method )
{
case ACPI_CSTATE_EM_FFH:
@@ -419,15 +428,19 @@ static void acpi_idle_do_entry(struct acpi_processor_cx
*cx)
acpi_processor_ffh_cstate_enter(cx);
return;
case ACPI_CSTATE_EM_SYSIO:
+ spec_ctrl_enter_idle(info);
/* IO port based C-state */
inb(cx->address);
/* Dummy wait op - must do something useless after P_LVL2 read
because chipsets cannot guarantee that STPCLK# signal
gets asserted in time to freeze execution properly. */
inl(pmtmr_ioport);
+ spec_ctrl_exit_idle(info);
return;
case ACPI_CSTATE_EM_HALT:
+ spec_ctrl_enter_idle(info);
safe_halt();
+ spec_ctrl_exit_idle(info);
local_irq_disable();
return;
}
@@ -555,7 +568,13 @@ static void acpi_processor_idle(void)
if ( pm_idle_save )
pm_idle_save();
else
+ {
+ struct cpu_info *info = get_cpu_info();
+
+ spec_ctrl_enter_idle(info);
safe_halt();
+ spec_ctrl_exit_idle(info);
+ }
return;
}
@@ -734,6 +753,7 @@ void acpi_dead_idle(void)
* Otherwise, CPU may still hold dirty data, breaking cache coherency,
* leading to strange errors.
*/
+ spec_ctrl_enter_idle(get_cpu_info());
wbinvd();
while ( 1 )
@@ -763,6 +783,7 @@ void acpi_dead_idle(void)
u32 address = cx->address;
u32 pmtmr_ioport_local = pmtmr_ioport;
+ spec_ctrl_enter_idle(get_cpu_info());
wbinvd();
while ( 1 )
diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index 6e65e38..e84ef0b 100644
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -58,6 +58,7 @@
#include <asm/hpet.h>
#include <asm/mwait.h>
#include <asm/msr.h>
+#include <asm/spec_ctrl.h>
#include <acpi/cpufreq/cpufreq.h>
#define MWAIT_IDLE_VERSION "0.4.1"
@@ -612,7 +613,13 @@ static void mwait_idle(void)
if (pm_idle_save)
pm_idle_save();
else
+ {
+ struct cpu_info *info = get_cpu_info();
+
+ spec_ctrl_enter_idle(info);
safe_halt();
+ spec_ctrl_exit_idle(info);
+ }
return;
}
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index a44bb69..a84b179 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -55,6 +55,7 @@
#include <asm/hvm/viridian.h>
#include <asm/debugreg.h>
#include <asm/msr.h>
+#include <asm/spec_ctrl.h>
#include <asm/traps.h>
#include <asm/nmi.h>
#include <asm/mce.h>
@@ -76,9 +77,15 @@ static void paravirt_ctxt_switch_to(struct vcpu *v);
static void default_idle(void)
{
+ struct cpu_info *info = get_cpu_info();
+
local_irq_disable();
if ( cpu_is_haltable(smp_processor_id()) )
+ {
+ spec_ctrl_enter_idle(info);
safe_halt();
+ spec_ctrl_exit_idle(info);
+ }
else
local_irq_enable();
}
@@ -90,6 +97,7 @@ void default_dead_idle(void)
* held by the CPUs spinning here indefinitely, and get discarded by
* a subsequent INIT.
*/
+ spec_ctrl_enter_idle(get_cpu_info());
wbinvd();
for ( ; ; )
halt();
diff --git a/xen/include/asm-x86/spec_ctrl.h b/xen/include/asm-x86/spec_ctrl.h
index 41dce15..39823af 100644
--- a/xen/include/asm-x86/spec_ctrl.h
+++ b/xen/include/asm-x86/spec_ctrl.h
@@ -20,7 +20,9 @@
#ifndef __X86_SPEC_CTRL_H__
#define __X86_SPEC_CTRL_H__
+#include <asm/alternative.h>
#include <asm/current.h>
+#include <asm/msr-index.h>
void init_speculation_mitigations(void);
@@ -35,6 +37,38 @@ static inline void init_shadow_spec_ctrl_state(void)
info->bti_ist_info = default_bti_ist_info;
}
+/* WARNING! `ret`, `call *`, `jmp *` not safe after this call. */
+static always_inline void spec_ctrl_enter_idle(struct cpu_info *info)
+{
+ uint32_t val = 0;
+
+ /*
+ * Latch the new shadow value, then enable shadowing, then update the MSR.
+ * There are no SMP issues here; only local processor ordering concerns.
+ */
+ info->shadow_spec_ctrl = val;
+ barrier();
+ info->use_shadow_spec_ctrl = 1;
+ barrier();
+ asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
+ :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
+}
+
+/* WARNING! `ret`, `call *`, `jmp *` not safe before this call. */
+static always_inline void spec_ctrl_exit_idle(struct cpu_info *info)
+{
+ uint32_t val = SPEC_CTRL_IBRS;
+
+ /*
+ * Disable shadowing before updating the MSR. There are no SMP issues
+ * here; only local processor ordering concerns.
+ */
+ info->use_shadow_spec_ctrl = 0;
+ barrier();
+ asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
+ :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
+}
+
#endif /* !__X86_SPEC_CTRL_H__ */
/*
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7
_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog
|
 |
Lists.xenproject.org is hosted with RackSpace, monitoring our |