linux.git/drivers/clocksource/arm_arch_timer.c, branch v7.2-rc1 Linux kernel source tree clocksource/drivers/arm_arch_timer: Default to EL2 virtual timer when running VHE 2026-06-03T07:53:21+00:00 Marc Zyngier maz@kernel.org 2026-05-23T14:02:28+00:00 d87773de9efe1df6fe2ba379926f9df92f1a5913 When running with at EL2 with VHE enabled, the architecture provides two EL2 timer/counters, dubbed physical and virtual. Apart from their names, they are strictly identical. However, they don't get virtualised the same way, specially when it comes to adding arbitrary offsets to the timers. When running as a guest, the host CNTVOFF_EL2 does apply to the guest's view of CNTHV*_El2. This is not true for CNTPOFF_EL2 and CNTHP*_EL2, as the architecture is broken past the first level of virtualisation (it lacks some essential mechanisms to be usable, despite what the ARM ARM pretends). This means that when running as a L2 guest hypervisor, using the physical timer results in traps to L0, which are then forwarded to L1 in order to emulate the offset, leading to even worse performance due to massive trap amplification (the combination of register and ERET trapping is absolutely lethal). Switch the arch timer code to using the virtual timer when running in VHE by default, only using the physical timer if the interrupt is not correctly described in the firmware tables (which seems to be an unfortunately common case). This comes as no impact on bare-metal, and slightly improves the situation in the virtualised case. Signed-off-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Daniel Lezcano <daniel.lezcano@kernel.org> Link: https://patch.msgid.link/20260523140242.586031-4-maz@kernel.org 
When running with at EL2 with VHE enabled, the architecture provides
two EL2 timer/counters, dubbed physical and virtual. Apart from their
names, they are strictly identical.

However, they don't get virtualised the same way, specially when
it comes to adding arbitrary offsets to the timers. When running as
a guest, the host CNTVOFF_EL2 does apply to the guest's view of
CNTHV*_El2. This is not true for CNTPOFF_EL2 and CNTHP*_EL2, as
the architecture is broken past the first level of virtualisation
(it lacks some essential mechanisms to be usable, despite what
the ARM ARM pretends).

This means that when running as a L2 guest hypervisor, using the
physical timer results in traps to L0, which are then forwarded to
L1 in order to emulate the offset, leading to even worse performance
due to massive trap amplification (the combination of register and
ERET trapping is absolutely lethal).

Switch the arch timer code to using the virtual timer when running
in VHE by default, only using the physical timer if the interrupt
is not correctly described in the firmware tables (which seems
to be an unfortunately common case). This comes as no impact on
bare-metal, and slightly improves the situation in the virtualised
case.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@kernel.org>
Link: https://patch.msgid.link/20260523140242.586031-4-maz@kernel.org
clocksource/drivers/arm_arch_timer_mmio: Switch over to standalone driver 2025-09-23T10:31:50+00:00 Marc Zyngier maz@kernel.org 2025-08-14T15:46:21+00:00 0f67b56d84b4c49adfd61f19f81f84ec613ab51a Remove all the MMIO support from the per-CPU timer driver, and switch over to the standalove driver. Signed-off-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Tested-by: Sudeep Holla <sudeep.holla@arm.com> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Link: https://lore.kernel.org/r/20250814154622.10193-4-maz@kernel.org 
Remove all the MMIO support from the per-CPU timer driver, and switch
over to the standalove driver.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20250814154622.10193-4-maz@kernel.org
time/timecounter: Fix the lie that struct cyclecounter is const 2025-07-01T13:38:25+00:00 Greg Kroah-Hartman gregkh@linuxfoundation.org 2025-07-01T12:32:25+00:00 e78f70bad29c5ae1e1076698b690b15794e9b81e In both the read callback for struct cyclecounter, and in struct timecounter, struct cyclecounter is declared as a const pointer. Unfortunatly, a number of users of this pointer treat it as a non-const pointer as it is burried in a larger structure that is heavily modified by the callback function when accessed. This lie had been hidden by the fact that container_of() "casts away" a const attribute of a pointer without any compiler warning happening at all. Fix this all up by removing the const attribute in the needed places so that everyone can see that the structure really isn't const, but can, and is, modified by the users of it. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/all/2025070124-backyard-hurt-783a@gregkh 
In both the read callback for struct cyclecounter, and in struct
timecounter, struct cyclecounter is declared as a const pointer.

Unfortunatly, a number of users of this pointer treat it as a non-const
pointer as it is burried in a larger structure that is heavily modified by
the callback function when accessed.  This lie had been hidden by the fact
that container_of() "casts away" a const attribute of a pointer without any
compiler warning happening at all.

Fix this all up by removing the const attribute in the needed places so
that everyone can see that the structure really isn't const, but can,
and is, modified by the users of it.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/2025070124-backyard-hurt-783a@gregkh
arm64: Modify _midr_range() functions to read MIDR/REVIDR internally 2025-02-26T21:29:44+00:00 Shameer Kolothum shameerali.kolothum.thodi@huawei.com 2025-02-21T14:02:24+00:00 e3121298c7fcaf488df8e61f50fced9a741c4c44 These changes lay the groundwork for adding support for guest kernels, allowing them to leverage target CPU implementations provided by the VMM. No functional changes intended. Suggested-by: Oliver Upton <oliver.upton@linux.dev> Reviewed-by: Sebastian Ott <sebott@redhat.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Link: https://lore.kernel.org/r/20250221140229.12588-2-shameerali.kolothum.thodi@huawei.com Signed-off-by: Oliver Upton <oliver.upton@linux.dev> 
These changes lay the groundwork for adding support for guest kernels,
allowing them to leverage target CPU implementations provided by the
VMM.

No functional changes intended.

Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Sebastian Ott <sebott@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20250221140229.12588-2-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
clocksource/drivers/arm_arch_timer: Use of_property_present() for non-boolean properties 2024-11-13T12:49:33+00:00 Rob Herring (Arm) robh@kernel.org 2024-11-04T19:05:06+00:00 08b97fbd13de79744b31d2b3c8a0ab1a409b94fa The use of of_property_read_bool() for non-boolean properties is deprecated in favor of of_property_present() when testing for property presence. Signed-off-by: Rob Herring (Arm) <robh@kernel.org> Link: https://lore.kernel.org/r/20241104190505.272805-2-robh@kernel.org Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> 
The use of of_property_read_bool() for non-boolean properties is
deprecated in favor of of_property_present() when testing for property
presence.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20241104190505.272805-2-robh@kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
clocksource/drivers/arm_arch_timer: Remove clockevents shutdown call on offlining 2024-10-31T09:41:42+00:00 Frederic Weisbecker frederic@kernel.org 2024-10-29T12:54:46+00:00 78b5c2ca5f27534dc04fbbe0b491dd3bd4ec814b The clockevents core already detached and unregistered it at this stage. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/all/20241029125451.54574-6-frederic@kernel.org 
The clockevents core already detached and unregistered it at this stage.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241029125451.54574-6-frederic@kernel.org
clocksource/drivers/arm_arch_timer: Using for_each_available_child_of_node_scoped() 2024-09-06T12:49:20+00:00 Zhang Zekun zhangzekun11@huawei.com 2024-08-07T07:46:55+00:00 a7456d7d1b8e781fdaa16c10947bd2363c6fd342 for_each_available_child_of_node_scoped() can put the device_node automatically. So, using it to make the code logic more simple and remove the device_node clean up code. Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com> Link: https://lore.kernel.org/r/20240807074655.52157-1-zhangzekun11@huawei.com Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> 
for_each_available_child_of_node_scoped() can put the device_node
automatically. So, using it to make the code logic more simple and
remove the device_node clean up code.

Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Link: https://lore.kernel.org/r/20240807074655.52157-1-zhangzekun11@huawei.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
clocksource/drivers/arm_arch_timer: Remove unnecessary ‘0’ values from irq 2024-07-12T14:07:05+00:00 Li kunyu kunyu@nfschina.com 2024-07-05T04:07:29+00:00 7cbbcbd4b5bb68a6208b872612bb301683dc7114 The irq variable is initialized whatever the code path, it is poinless to initialize when declaring it. Signed-off-by: Li kunyu <kunyu@nfschina.com> Link: https://lore.kernel.org/r/20240705040729.21961-1-kunyu@nfschina.com Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> 
The irq variable is initialized whatever the code path, it is poinless
to initialize when declaring it.

Signed-off-by: Li kunyu <kunyu@nfschina.com>
Link: https://lore.kernel.org/r/20240705040729.21961-1-kunyu@nfschina.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
clocksource/drivers/arm_arch_timer: Mark hisi_161010101_oem_info const 2024-05-10T08:43:21+00:00 Stephen Boyd swboyd@chromium.org 2024-05-02T23:34:46+00:00 2030a7e11f161b4067bd4eadd984cdb36446fcca This isn't modified at runtime. Mark it const so it can move to read-only data. Cc: dann frazier <dann.frazier@canonical.com> Cc: Hanjun Guo <hanjun.guo@linaro.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <swboyd@chromium.org> Reviewed-by: Hanjun Guo <guohanjun@huawei.com> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Link: https://lore.kernel.org/r/20240502233447.420888-1-swboyd@chromium.org 
This isn't modified at runtime. Mark it const so it can move to
read-only data.

Cc: dann frazier <dann.frazier@canonical.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240502233447.420888-1-swboyd@chromium.org
treewide: Remove system_counterval_t.cs, which is never read 2024-02-07T16:05:21+00:00 Peter Hilber peter.hilber@opensynergy.com 2024-02-01T01:04:52+00:00 b152688c91313ab4073cff4a5e63ff4cc491c358 The clocksource pointer in struct system_counterval_t is not evaluated any more. Remove the code setting the member, and the member itself. Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240201010453.2212371-8-peter.hilber@opensynergy.com 
The clocksource pointer in struct system_counterval_t is not evaluated any
more. Remove the code setting the member, and the member itself.

Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240201010453.2212371-8-peter.hilber@opensynergy.com