[v6] Enable haltpoll on arm64

[PATCH v6 03/10] Kconfig: move ARCH_HAS_OPTIMIZED_POLL to arch/Kconfig

Posted by Ankur Arora 2 months, 3 weeks ago

From: Joao Martins <joao.m.martins@oracle.com>

ARCH_HAS_OPTIMIZED_POLL gates selection of polling while idle in
poll_idle(). Move the configuration option to arch/Kconfig to allow
non-x86 architectures to select it.

Note that ARCH_HAS_OPTIMIZED_POLL should probably be exclusive with
GENERIC_IDLE_POLL_SETUP (which controls the generic polling logic in
cpu_idle_poll()). However, that would remove boot options
(hlt=, nohlt=). So, leave it untouched for now.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/Kconfig     | 3 +++
 arch/x86/Kconfig | 4 +---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 975dd22a2dbd..d43894369015 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -264,6 +264,9 @@ config HAVE_ARCH_TRACEHOOK
 config HAVE_DMA_CONTIGUOUS
 	bool
 
+config ARCH_HAS_OPTIMIZED_POLL
+	bool
+
 config GENERIC_SMP_IDLE_THREAD
 	bool
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cf78da2ba8fb..efe59741dc47 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -134,6 +134,7 @@ config X86
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_GENERAL_HUGETLB
 	select ARCH_WANT_HUGE_PMD_SHARE
+	select ARCH_HAS_OPTIMIZED_POLL
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP	if X86_64
 	select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP	if X86_64
@@ -372,9 +373,6 @@ config ARCH_MAY_HAVE_PC_FDC
 config GENERIC_CALIBRATE_DELAY
 	def_bool y
 
-config ARCH_HAS_OPTIMIZED_POLL
-	def_bool y
-
 config ARCH_HIBERNATION_POSSIBLE
 	def_bool y
 
-- 
2.43.5

[PATCH v6 04/10] cpuidle-haltpoll: define arch_haltpoll_want()

Posted by Ankur Arora 2 months, 3 weeks ago

From: Joao Martins <joao.m.martins@oracle.com>

kvm_para_has_hint(KVM_HINTS_REALTIME) is defined only on x86. In
pursuit of making cpuidle-haltpoll architecture independent, define
arch_haltpoll_want() which handles the architectural checks for
enabling haltpoll.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/x86/include/asm/cpuidle_haltpoll.h |  1 +
 arch/x86/kernel/kvm.c                   | 13 +++++++++++++
 drivers/cpuidle/cpuidle-haltpoll.c      | 12 +-----------
 include/linux/cpuidle_haltpoll.h        |  5 +++++
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/cpuidle_haltpoll.h b/arch/x86/include/asm/cpuidle_haltpoll.h
index c8b39c6716ff..8a0a12769c2e 100644
--- a/arch/x86/include/asm/cpuidle_haltpoll.h
+++ b/arch/x86/include/asm/cpuidle_haltpoll.h
@@ -4,5 +4,6 @@
 
 void arch_haltpoll_enable(unsigned int cpu);
 void arch_haltpoll_disable(unsigned int cpu);
+bool arch_haltpoll_want(bool force);
 
 #endif
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 263f8aed4e2c..63710cb1aa63 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -1151,4 +1151,17 @@ void arch_haltpoll_disable(unsigned int cpu)
 	smp_call_function_single(cpu, kvm_enable_host_haltpoll, NULL, 1);
 }
 EXPORT_SYMBOL_GPL(arch_haltpoll_disable);
+
+bool arch_haltpoll_want(bool force)
+{
+	/* Do not load haltpoll if idle= is passed */
+	if (boot_option_idle_override != IDLE_NO_OVERRIDE)
+		return false;
+
+	if (!kvm_para_available())
+		return false;
+
+	return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
+}
+EXPORT_SYMBOL_GPL(arch_haltpoll_want);
 #endif
diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
index d8515d5c0853..d47906632ce3 100644
--- a/drivers/cpuidle/cpuidle-haltpoll.c
+++ b/drivers/cpuidle/cpuidle-haltpoll.c
@@ -15,7 +15,6 @@
 #include <linux/cpuidle.h>
 #include <linux/module.h>
 #include <linux/sched/idle.h>
-#include <linux/kvm_para.h>
 #include <linux/cpuidle_haltpoll.h>
 
 static bool force __read_mostly;
@@ -93,21 +92,12 @@ static void haltpoll_uninit(void)
 	haltpoll_cpuidle_devices = NULL;
 }
 
-static bool haltpoll_want(void)
-{
-	return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
-}
-
 static int __init haltpoll_init(void)
 {
 	int ret;
 	struct cpuidle_driver *drv = &haltpoll_driver;
 
-	/* Do not load haltpoll if idle= is passed */
-	if (boot_option_idle_override != IDLE_NO_OVERRIDE)
-		return -ENODEV;
-
-	if (!kvm_para_available() || !haltpoll_want())
+	if (!arch_haltpoll_want(force))
 		return -ENODEV;
 
 	cpuidle_poll_state_init(drv);
diff --git a/include/linux/cpuidle_haltpoll.h b/include/linux/cpuidle_haltpoll.h
index d50c1e0411a2..68eb7a757120 100644
--- a/include/linux/cpuidle_haltpoll.h
+++ b/include/linux/cpuidle_haltpoll.h
@@ -12,5 +12,10 @@ static inline void arch_haltpoll_enable(unsigned int cpu)
 static inline void arch_haltpoll_disable(unsigned int cpu)
 {
 }
+
+static inline bool arch_haltpoll_want(bool force)
+{
+	return false;
+}
 #endif
 #endif
-- 
2.43.5

[PATCH v6 05/10] governors/haltpoll: drop kvm_para_available() check

Posted by Ankur Arora 2 months, 3 weeks ago

From: Joao Martins <joao.m.martins@oracle.com>

The haltpoll governor is selected either by the cpuidle-haltpoll
driver, or explicitly by the user.
In particular, it is never selected by default since it has the lowest
rating of all governors (menu=20, teo=19, ladder=10/25, haltpoll=9).

So, we can safely forgo the kvm_para_available() check. This also
allows cpuidle-haltpoll to be tested on baremetal.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Acked-by: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 drivers/cpuidle/governors/haltpoll.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
index 663b7f164d20..c8752f793e61 100644
--- a/drivers/cpuidle/governors/haltpoll.c
+++ b/drivers/cpuidle/governors/haltpoll.c
@@ -18,7 +18,6 @@
 #include <linux/tick.h>
 #include <linux/sched.h>
 #include <linux/module.h>
-#include <linux/kvm_para.h>
 #include <trace/events/power.h>
 
 static unsigned int guest_halt_poll_ns __read_mostly = 200000;
@@ -148,10 +147,7 @@ static struct cpuidle_governor haltpoll_governor = {
 
 static int __init init_haltpoll(void)
 {
-	if (kvm_para_available())
-		return cpuidle_register_governor(&haltpoll_governor);
-
-	return 0;
+	return cpuidle_register_governor(&haltpoll_governor);
 }
 
 postcore_initcall(init_haltpoll);
-- 
2.43.5

[PATCH v6 06/10] cpuidle-haltpoll: condition on ARCH_CPUIDLE_HALTPOLL

Posted by Ankur Arora 2 months, 3 weeks ago

The cpuidle-haltpoll driver and its namesake governor are selected
under KVM_GUEST on X86. KVM_GUEST in-turn selects ARCH_CPUIDLE_HALTPOLL
and defines the requisite arch_haltpoll_{enable,disable}() functions.

So remove the explicit dependence of HALTPOLL_CPUIDLE on KVM_GUEST,
and instead use ARCH_CPUIDLE_HALTPOLL as proxy for architectural
support for haltpoll.

Also change "halt poll" to "haltpoll" in one of the summary clauses,
since the second form is used everywhere else.

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/x86/Kconfig        | 1 +
 drivers/cpuidle/Kconfig | 5 ++---
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index efe59741dc47..153535e6f55d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -838,6 +838,7 @@ config KVM_GUEST
 
 config ARCH_CPUIDLE_HALTPOLL
 	def_bool n
+	depends on KVM_GUEST
 	prompt "Disable host haltpoll when loading haltpoll driver"
 	help
 	  If virtualized under KVM, disable host haltpoll.
diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index 75f6e176bbc8..c1bebadf22bc 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -35,7 +35,6 @@ config CPU_IDLE_GOV_TEO
 
 config CPU_IDLE_GOV_HALTPOLL
 	bool "Haltpoll governor (for virtualized systems)"
-	depends on KVM_GUEST
 	help
 	  This governor implements haltpoll idle state selection, to be
 	  used in conjunction with the haltpoll cpuidle driver, allowing
@@ -72,8 +71,8 @@ source "drivers/cpuidle/Kconfig.riscv"
 endmenu
 
 config HALTPOLL_CPUIDLE
-	tristate "Halt poll cpuidle driver"
-	depends on X86 && KVM_GUEST && ARCH_HAS_OPTIMIZED_POLL
+	tristate "Haltpoll cpuidle driver"
+	depends on ARCH_CPUIDLE_HALTPOLL && ARCH_HAS_OPTIMIZED_POLL
 	select CPU_IDLE_GOV_HALTPOLL
 	default y
 	help
-- 
2.43.5

[PATCH v6 07/10] arm64: define TIF_POLLING_NRFLAG

Posted by Ankur Arora 2 months, 3 weeks ago

From: Joao Martins <joao.m.martins@oracle.com>

Commit 842514849a61 ("arm64: Remove TIF_POLLING_NRFLAG") had removed
TIF_POLLING_NRFLAG because arm64 only supported non-polled idling via
cpu_do_idle().

To add support for polling via cpuidle-haltpoll, we want to use the
standard poll_idle() interface, which sets TIF_POLLING_NRFLAG while
polling.

Reuse the same bit to define TIF_POLLING_NRFLAG.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/arm64/include/asm/thread_info.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index e72a3bf9e563..23ff72168e48 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -69,6 +69,7 @@ void arch_setup_new_exec(void);
 #define TIF_SYSCALL_TRACEPOINT	10	/* syscall tracepoint for ftrace */
 #define TIF_SECCOMP		11	/* syscall secure computing */
 #define TIF_SYSCALL_EMU		12	/* syscall emulation active */
+#define TIF_POLLING_NRFLAG	16	/* set while polling in poll_idle() */
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 #define TIF_FREEZE		19
 #define TIF_RESTORE_SIGMASK	20
@@ -91,6 +92,7 @@ void arch_setup_new_exec(void);
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_SYSCALL_EMU	(1 << TIF_SYSCALL_EMU)
+#define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)
 #define _TIF_32BIT		(1 << TIF_32BIT)
-- 
2.43.5

[PATCH v6 08/10] arm64: idle: export arch_cpu_idle

Posted by Ankur Arora 2 months, 3 weeks ago

Needed for cpuidle-haltpoll.

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/arm64/kernel/idle.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c
index 05cfb347ec26..b85ba0df9b02 100644
--- a/arch/arm64/kernel/idle.c
+++ b/arch/arm64/kernel/idle.c
@@ -43,3 +43,4 @@ void __cpuidle arch_cpu_idle(void)
 	 */
 	cpu_do_idle();
 }
+EXPORT_SYMBOL_GPL(arch_cpu_idle);
-- 
2.43.5

[PATCH v6 09/10] arm64: support cpuidle-haltpoll

Posted by Ankur Arora 2 months, 3 weeks ago

Add architectural support for cpuidle-haltpoll driver by defining
arch_haltpoll_*().

Also define ARCH_CPUIDLE_HALTPOLL to allow cpuidle-haltpoll to be
selected, and given that we have an optimized polling mechanism
in smp_cond_load*(), select ARCH_HAS_OPTIMIZED_POLL.

smp_cond_load*() are implemented via LDXR, WFE, with LDXR loading
a memory region in exclusive state and the WFE waiting for any
stores to it.

In the edge case -- no CPU stores to the waited region and there's no
interrupt -- the event-stream will provide the terminating condition
ensuring we don't wait forever, but because the event-stream runs at
a fixed frequency (configured at 10kHz) we might spend more time in
the polling stage than specified by cpuidle_poll_time().

This would only happen in the last iteration, since overshooting the
poll_limit means the governor moves out of the polling stage.

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/arm64/Kconfig                        | 10 ++++++++++
 arch/arm64/include/asm/cpuidle_haltpoll.h |  9 +++++++++
 arch/arm64/kernel/cpuidle.c               | 23 +++++++++++++++++++++++
 3 files changed, 42 insertions(+)
 create mode 100644 arch/arm64/include/asm/cpuidle_haltpoll.h

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 5d91259ee7b5..cf1c6681eb0a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -35,6 +35,7 @@ config ARM64
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+	select ARCH_HAS_OPTIMIZED_POLL
 	select ARCH_HAS_PTE_DEVMAP
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_HW_PTE_YOUNG
@@ -2376,6 +2377,15 @@ config ARCH_HIBERNATION_HEADER
 config ARCH_SUSPEND_POSSIBLE
 	def_bool y
 
+config ARCH_CPUIDLE_HALTPOLL
+	bool "Enable selection of the cpuidle-haltpoll driver"
+	default n
+	help
+	  cpuidle-haltpoll allows for adaptive polling based on
+	  current load before entering the idle state.
+
+	  Some virtualized workloads benefit from using it.
+
 endmenu # "Power management options"
 
 menu "CPU Power Management"
diff --git a/arch/arm64/include/asm/cpuidle_haltpoll.h b/arch/arm64/include/asm/cpuidle_haltpoll.h
new file mode 100644
index 000000000000..65f289407a6c
--- /dev/null
+++ b/arch/arm64/include/asm/cpuidle_haltpoll.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ARCH_HALTPOLL_H
+#define _ARCH_HALTPOLL_H
+
+static inline void arch_haltpoll_enable(unsigned int cpu) { }
+static inline void arch_haltpoll_disable(unsigned int cpu) { }
+
+bool arch_haltpoll_want(bool force);
+#endif
diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c
index f372295207fb..334df82a0eac 100644
--- a/arch/arm64/kernel/cpuidle.c
+++ b/arch/arm64/kernel/cpuidle.c
@@ -72,3 +72,26 @@ __cpuidle int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
 					     lpi->index, state);
 }
 #endif
+
+#if IS_ENABLED(CONFIG_HALTPOLL_CPUIDLE)
+
+#include <asm/cpuidle_haltpoll.h>
+
+bool arch_haltpoll_want(bool force)
+{
+	/*
+	 * Enabling haltpoll requires two things:
+	 *
+	 * - Event stream support to provide a terminating condition to the
+	 *   WFE in the poll loop.
+	 *
+	 * - KVM support for arch_haltpoll_enable(), arch_haltpoll_enable().
+	 *
+	 * Given that the second is missing, allow haltpoll to only be force
+	 * loaded.
+	 */
+	return (arch_timer_evtstrm_available() && false) || force;
+}
+
+EXPORT_SYMBOL_GPL(arch_haltpoll_want);
+#endif
-- 
2.43.5