[Xen-devel] [RFC 3/6] arm/arm64: clocksource: Introduce vclock_mode

[Boqun Feng <boqun.feng@xxxxxxxxx>]

Similar to x86, use a vclock_mode in arch_clocksource_data to differ
clocksoures use different read function in vDSO.

No functional changes, only preparation for support vDSO in ARM64 on
Hyper-V.

Note: the changes for arm are only because arm and arm64 share the same
code in the arch timer driver and require arch_clocksource_data having
the same field.

Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@xxxxxxxxx>
---
 arch/arm/include/asm/clocksource.h                | 6 +++++-
 arch/arm/kernel/vdso.c                            | 1 -
 arch/arm64/include/asm/clocksource.h              | 6 +++++-
 arch/arm64/include/asm/mshyperv.h                 | 2 +-
 arch/arm64/include/asm/vdso/compat_gettimeofday.h | 5 +++--
 arch/arm64/include/asm/vdso/gettimeofday.h        | 5 +++--
 arch/arm64/include/asm/vdso/vsyscall.h            | 4 +---
 drivers/clocksource/arm_arch_timer.c              | 8 ++++----
 8 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/arch/arm/include/asm/clocksource.h 
b/arch/arm/include/asm/clocksource.h
index 0b350a7e26f3..017c5ab6e587 100644
--- a/arch/arm/include/asm/clocksource.h
+++ b/arch/arm/include/asm/clocksource.h
@@ -1,8 +1,12 @@
 #ifndef _ASM_CLOCKSOURCE_H
 #define _ASM_CLOCKSOURCE_H
 
+#define VCLOCK_NONE    0       /* No vDSO clock available.             */
+#define VCLOCK_CNTVCT  1       /* vDSO should use cntvcnt              */
+#define VCLOCK_MAX     1
+
 struct arch_clocksource_data {
-       bool vdso_direct;       /* Usable for direct VDSO access? */
+       int vclock_mode;
 };
 
 #endif
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index c89ac1b9d28b..09e46ec420fe 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -263,4 +263,3 @@ void arm_install_vdso(struct mm_struct *mm, unsigned long 
addr)
        if (!IS_ERR(vma))
                mm->context.vdso = addr;
 }
-
diff --git a/arch/arm64/include/asm/clocksource.h 
b/arch/arm64/include/asm/clocksource.h
index 0ece64a26c8c..fbe80057468c 100644
--- a/arch/arm64/include/asm/clocksource.h
+++ b/arch/arm64/include/asm/clocksource.h
@@ -2,8 +2,12 @@
 #ifndef _ASM_CLOCKSOURCE_H
 #define _ASM_CLOCKSOURCE_H
 
+#define VCLOCK_NONE    0       /* No vDSO clock available.             */
+#define VCLOCK_CNTVCT  1       /* vDSO should use cntvcnt              */
+#define VCLOCK_MAX     1
+
 struct arch_clocksource_data {
-       bool vdso_direct;       /* Usable for direct VDSO access? */
+       int vclock_mode;
 };
 
 #endif
diff --git a/arch/arm64/include/asm/mshyperv.h 
b/arch/arm64/include/asm/mshyperv.h
index 9cc4aeddf2d0..0afb00e3501d 100644
--- a/arch/arm64/include/asm/mshyperv.h
+++ b/arch/arm64/include/asm/mshyperv.h
@@ -90,7 +90,7 @@ extern void hv_get_vpreg_128(u32 reg, struct 
hv_get_vp_register_output *result);
 #define hv_set_reference_tsc(val) \
                hv_set_vpreg(HV_REGISTER_REFERENCE_TSC, val)
 #define hv_set_clocksource_vdso(val) \
-               ((val).archdata.vdso_direct = false)
+               ((val).archdata.vclock_mode = VCLOCK_NONE)
 
 #if IS_ENABLED(CONFIG_HYPERV)
 #define hv_enable_stimer0_percpu_irq(irq)      enable_percpu_irq(irq, 0)
diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h 
b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
index c50ee1b7d5cd..630d04c3c92e 100644
--- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
@@ -8,6 +8,7 @@
 #ifndef __ASSEMBLY__
 
 #include <asm/unistd.h>
+#include <asm/clocksource.h>
 #include <uapi/linux/time.h>
 
 #include <asm/vdso/compat_barrier.h>
@@ -117,10 +118,10 @@ static __always_inline u64 __arch_get_hw_counter(s32 
clock_mode)
        u64 res;
 
        /*
-        * clock_mode == 0 implies that vDSO are enabled otherwise
+        * clock_mode == VCLOCK_NONE implies that vDSO are disabled so
         * fallback on syscall.
         */
-       if (clock_mode)
+       if (clock_mode == VCLOCK_NONE)
                return __VDSO_USE_SYSCALL;
 
        /*
diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h 
b/arch/arm64/include/asm/vdso/gettimeofday.h
index b08f476b72b4..e6e3fe0488c7 100644
--- a/arch/arm64/include/asm/vdso/gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/gettimeofday.h
@@ -8,6 +8,7 @@
 #ifndef __ASSEMBLY__
 
 #include <asm/unistd.h>
+#include <asm/clocksource.h>
 #include <uapi/linux/time.h>
 
 #define __VDSO_USE_SYSCALL             ULLONG_MAX
@@ -71,10 +72,10 @@ static __always_inline u64 __arch_get_hw_counter(s32 
clock_mode)
        u64 res;
 
        /*
-        * clock_mode == 0 implies that vDSO are enabled otherwise
+        * clock_mode == VCLOCK_NONE implies that vDSO are disabled so
         * fallback on syscall.
         */
-       if (clock_mode)
+       if (clock_mode == VCLOCK_NONE)
                return __VDSO_USE_SYSCALL;
 
        /*
diff --git a/arch/arm64/include/asm/vdso/vsyscall.h 
b/arch/arm64/include/asm/vdso/vsyscall.h
index 0c20a7c1bee5..07f78b0da498 100644
--- a/arch/arm64/include/asm/vdso/vsyscall.h
+++ b/arch/arm64/include/asm/vdso/vsyscall.h
@@ -24,9 +24,7 @@ struct vdso_data *__arm64_get_k_vdso_data(void)
 static __always_inline
 int __arm64_get_clock_mode(struct timekeeper *tk)
 {
-       u32 use_syscall = !tk->tkr_mono.clock->archdata.vdso_direct;
-
-       return use_syscall;
+       return tk->tkr_mono.clock->archdata.vclock_mode;
 }
 #define __arch_get_clock_mode __arm64_get_clock_mode
 
diff --git a/drivers/clocksource/arm_arch_timer.c 
b/drivers/clocksource/arm_arch_timer.c
index 9a5464c625b4..9b8d4d00b53b 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -69,7 +69,7 @@ static enum arch_timer_ppi_nr arch_timer_uses_ppi = 
ARCH_TIMER_VIRT_PPI;
 static bool arch_timer_c3stop;
 static bool arch_timer_mem_use_virtual;
 static bool arch_counter_suspend_stop;
-static bool vdso_default = true;
+static int vdso_default = VCLOCK_CNTVCT;
 
 static cpumask_t evtstrm_available = CPU_MASK_NONE;
 static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
@@ -560,8 +560,8 @@ void arch_timer_enable_workaround(const struct 
arch_timer_erratum_workaround *wa
         * change both the default value and the vdso itself.
         */
        if (wa->read_cntvct_el0) {
-               clocksource_counter.archdata.vdso_direct = false;
-               vdso_default = false;
+               clocksource_counter.archdata.vclock_mode = VCLOCK_NONE;
+               vdso_default = VCLOCK_NONE;
        }
 }
 
@@ -979,7 +979,7 @@ static void __init arch_counter_register(unsigned type)
                }
 
                arch_timer_read_counter = rd;
-               clocksource_counter.archdata.vdso_direct = vdso_default;
+               clocksource_counter.archdata.vclock_mode = vdso_default;
        } else {
                arch_timer_read_counter = arch_counter_get_cntvct_mem;
        }
-- 
2.24.0


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