Re: [PATCH v4 1/9] clocksource: arm_arch_timer: Gather KVM specific information in a structure

From: Daniel Lezcano
Date: Tue Mar 29 2016 - 13:14:19 EST

On 03/24/2016 06:53 PM, Julien Grall wrote:
Introduce a structure which are filled up by the arch timer driver and
used by the virtual timer in KVM.

The first member of this structure will be the timecounter. More members
will be added later.

A stub for the new helper isn't introduced because KVM requires the arch
timer for both ARM64 and ARM32.

The function arch_timer_get_timecounter is kept for the time being and
will be dropped in a subsequent patch.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>

Changes in v3:
- Rename the patch
- Move the KVM changes and removal of arch_timer_get_timecounter
in separate patches.
drivers/clocksource/arm_arch_timer.c | 12 +++++++++---
include/clocksource/arm_arch_timer.h | 5 +++++
2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 5152b38..62bdfe7 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -468,11 +468,16 @@ static struct cyclecounter cyclecounter = {

-static struct timecounter timecounter;
+static struct arch_timer_kvm_info arch_timer_kvm_info;

This structure is statically defined in this subsystem but not used in this file and a couple of a accessors is added to let another subsystem to access it.

That sounds there is something wrong here with the design of the current code, virt/phys are mixed.

It isn't possible to split the virt/phys timer code respectively in virt/kvm/arm/arch_timer.c and drivers/clocksource/arm_arch_timer.c ?

At least, 'struct arch_timer_kvm_info' should belong to virt/kvm/arm/arch_timer.c.

+struct arch_timer_kvm_info *arch_timer_get_kvm_info(void)
+ return &arch_timer_kvm_info;

struct timecounter *arch_timer_get_timecounter(void)
- return &timecounter;
+ return &arch_timer_kvm_info.timecounter;

static void __init arch_counter_register(unsigned type)
@@ -500,7 +505,8 @@ static void __init arch_counter_register(unsigned type)
clocksource_register_hz(&clocksource_counter, arch_timer_rate);
cyclecounter.mult = clocksource_counter.mult;
cyclecounter.shift = clocksource_counter.shift;
- timecounter_init(&timecounter, &cyclecounter, start_count);
+ timecounter_init(&arch_timer_kvm_info.timecounter,
+ &cyclecounter, start_count);

/* 56 bits minimum, so we assume worst case rollover */
sched_clock_register(arch_timer_read_counter, 56, arch_timer_rate);
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index 25d0914..9101ed6b 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -49,11 +49,16 @@ enum arch_timer_reg {

#define ARCH_TIMER_EVT_STREAM_FREQ 10000 /* 100us */

+struct arch_timer_kvm_info {
+ struct timecounter timecounter;

extern u32 arch_timer_get_rate(void);
extern u64 (*arch_timer_read_counter)(void);
extern struct timecounter *arch_timer_get_timecounter(void);
+extern struct arch_timer_kvm_info *arch_timer_get_kvm_info(void);


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