Re: [Xen-devel] [RFC 6/6] arm64: hyperv: Enable vDSO
On Tue, Dec 17, 2019 at 03:10:16PM +0100, Vitaly Kuznetsov wrote:
> Boqun Feng writes:
>
> > Similar to x86, add a new vclock_mode VCLOCK_HVCLOCK, and reuse the
> > hv_read_tsc_page() for userspace to read tsc page clocksource.
> >
> > Signed-off-by: Boqun Feng (Microsoft)
> > ---
> > arch/arm64/include/asm/clocksource.h | 3 ++-
> > arch/arm64/include/asm/mshyperv.h | 2 +-
> > arch/arm64/include/asm/vdso/gettimeofday.h | 19 +++
> > 3 files changed, 22 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/clocksource.h
> > b/arch/arm64/include/asm/clocksource.h
> > index fbe80057468c..c6acd45fe748 100644
> > --- a/arch/arm64/include/asm/clocksource.h
> > +++ b/arch/arm64/include/asm/clocksource.h
> > @@ -4,7 +4,8 @@
> >
> > #define VCLOCK_NONE0 /* No vDSO clock available.
> > */
> > #define VCLOCK_CNTVCT 1 /* vDSO should use cntvcnt
> > */
> > -#define VCLOCK_MAX 1
> > +#define VCLOCK_HVCLOCK 2 /* vDSO should use vread_hvclock()
> > */
> > +#define VCLOCK_MAX 2
> >
> > struct arch_clocksource_data {
> > int vclock_mode;
> > diff --git a/arch/arm64/include/asm/mshyperv.h
> > b/arch/arm64/include/asm/mshyperv.h
> > index 0afb00e3501d..7c85dd816dca 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.vclock_mode = VCLOCK_NONE)
> > + ((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
> >
> > #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/gettimeofday.h
> > b/arch/arm64/include/asm/vdso/gettimeofday.h
> > index e6e3fe0488c7..7e689b903f4d 100644
> > --- a/arch/arm64/include/asm/vdso/gettimeofday.h
> > +++ b/arch/arm64/include/asm/vdso/gettimeofday.h
> > @@ -67,6 +67,20 @@ int clock_getres_fallback(clockid_t _clkid, struct
> > __kernel_timespec *_ts)
> > return ret;
> > }
> >
> > +#ifdef CONFIG_HYPERV_TIMER
> > +/* This will override the default hv_get_raw_timer() */
> > +#define hv_get_raw_timer() __arch_counter_get_cntvct()
> > +#include
> > +
> > +extern struct ms_hyperv_tsc_page
> > +_hvclock_page __attribute__((visibility("hidden")));
> > +
> > +static u64 vread_hvclock(void)
> > +{
> > + return hv_read_tsc_page(&_hvclock_page);
> > +}
> > +#endif
>
> The function is almost the same on x86 (&_hvclock_page ->
> _page), would it maybe make sense to move this to arch neutral
> clocksource/hyperv_timer.h?
>
I'm not sure whether the underscore matters in the vDSO data symbol, so
I follow the architectural name convention. If the leading underscore
doesn't have special purpose I'm happy to move this to arch neutral
header file.
> > +
> > static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
> > {
> > u64 res;
> > @@ -78,6 +92,11 @@ static __always_inline u64 __arch_get_hw_counter(s32
> > clock_mode)
> > if (clock_mode == VCLOCK_NONE)
> > return __VDSO_USE_SYSCALL;
> >
> > +#ifdef CONFIG_HYPERV_TIMER
> > + if (likely(clock_mode == VCLOCK_HVCLOCK))
> > + return vread_hvclock();
>
> I'm not sure likely() is justified here: it'll make ALL builds which
> enable CONFIG_HYPERV_TIMER (e.g. distro kernels) to prefer
> VCLOCK_HVCLOCK, even if the kernel is not running on Hyper-V.
>
Make sense. Thanks for pointing this out! I will change it in the next
version.
Regards,
Boqun
> > +#endif
> > +
> > /*
> > * This isb() is required to prevent that the counter value
> > * is speculated.
>
> --
> Vitaly
>
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Re: [Xen-devel] [RFC 6/6] arm64: hyperv: Enable vDSO
Boqun Feng writes:
> Similar to x86, add a new vclock_mode VCLOCK_HVCLOCK, and reuse the
> hv_read_tsc_page() for userspace to read tsc page clocksource.
>
> Signed-off-by: Boqun Feng (Microsoft)
> ---
> arch/arm64/include/asm/clocksource.h | 3 ++-
> arch/arm64/include/asm/mshyperv.h | 2 +-
> arch/arm64/include/asm/vdso/gettimeofday.h | 19 +++
> 3 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/clocksource.h
> b/arch/arm64/include/asm/clocksource.h
> index fbe80057468c..c6acd45fe748 100644
> --- a/arch/arm64/include/asm/clocksource.h
> +++ b/arch/arm64/include/asm/clocksource.h
> @@ -4,7 +4,8 @@
>
> #define VCLOCK_NONE 0 /* No vDSO clock available. */
> #define VCLOCK_CNTVCT1 /* vDSO should use cntvcnt
> */
> -#define VCLOCK_MAX 1
> +#define VCLOCK_HVCLOCK 2 /* vDSO should use vread_hvclock()
> */
> +#define VCLOCK_MAX 2
>
> struct arch_clocksource_data {
> int vclock_mode;
> diff --git a/arch/arm64/include/asm/mshyperv.h
> b/arch/arm64/include/asm/mshyperv.h
> index 0afb00e3501d..7c85dd816dca 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.vclock_mode = VCLOCK_NONE)
> + ((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
>
> #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/gettimeofday.h
> b/arch/arm64/include/asm/vdso/gettimeofday.h
> index e6e3fe0488c7..7e689b903f4d 100644
> --- a/arch/arm64/include/asm/vdso/gettimeofday.h
> +++ b/arch/arm64/include/asm/vdso/gettimeofday.h
> @@ -67,6 +67,20 @@ int clock_getres_fallback(clockid_t _clkid, struct
> __kernel_timespec *_ts)
> return ret;
> }
>
> +#ifdef CONFIG_HYPERV_TIMER
> +/* This will override the default hv_get_raw_timer() */
> +#define hv_get_raw_timer() __arch_counter_get_cntvct()
> +#include
> +
> +extern struct ms_hyperv_tsc_page
> +_hvclock_page __attribute__((visibility("hidden")));
> +
> +static u64 vread_hvclock(void)
> +{
> + return hv_read_tsc_page(&_hvclock_page);
> +}
> +#endif
The function is almost the same on x86 (&_hvclock_page ->
_page), would it maybe make sense to move this to arch neutral
clocksource/hyperv_timer.h?
> +
> static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
> {
> u64 res;
> @@ -78,6 +92,11 @@ static __always_inline u64 __arch_get_hw_counter(s32
> clock_mode)
> if (clock_mode == VCLOCK_NONE)
> return __VDSO_USE_SYSCALL;
>
> +#ifdef CONFIG_HYPERV_TIMER
> + if (likely(clock_mode == VCLOCK_HVCLOCK))
> + return vread_hvclock();
I'm not sure likely() is justified here: it'll make ALL builds which
enable CONFIG_HYPERV_TIMER (e.g. distro kernels) to prefer
VCLOCK_HVCLOCK, even if the kernel is not running on Hyper-V.
> +#endif
> +
> /*
>* This isb() is required to prevent that the counter value
>* is speculated.
--
Vitaly
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[Xen-devel] [RFC 6/6] arm64: hyperv: Enable vDSO
Similar to x86, add a new vclock_mode VCLOCK_HVCLOCK, and reuse the
hv_read_tsc_page() for userspace to read tsc page clocksource.
Signed-off-by: Boqun Feng (Microsoft)
---
arch/arm64/include/asm/clocksource.h | 3 ++-
arch/arm64/include/asm/mshyperv.h | 2 +-
arch/arm64/include/asm/vdso/gettimeofday.h | 19 +++
3 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/clocksource.h
b/arch/arm64/include/asm/clocksource.h
index fbe80057468c..c6acd45fe748 100644
--- a/arch/arm64/include/asm/clocksource.h
+++ b/arch/arm64/include/asm/clocksource.h
@@ -4,7 +4,8 @@
#define VCLOCK_NONE0 /* No vDSO clock available. */
#define VCLOCK_CNTVCT 1 /* vDSO should use cntvcnt */
-#define VCLOCK_MAX 1
+#define VCLOCK_HVCLOCK 2 /* vDSO should use vread_hvclock() */
+#define VCLOCK_MAX 2
struct arch_clocksource_data {
int vclock_mode;
diff --git a/arch/arm64/include/asm/mshyperv.h
b/arch/arm64/include/asm/mshyperv.h
index 0afb00e3501d..7c85dd816dca 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.vclock_mode = VCLOCK_NONE)
+ ((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
#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/gettimeofday.h
b/arch/arm64/include/asm/vdso/gettimeofday.h
index e6e3fe0488c7..7e689b903f4d 100644
--- a/arch/arm64/include/asm/vdso/gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/gettimeofday.h
@@ -67,6 +67,20 @@ int clock_getres_fallback(clockid_t _clkid, struct
__kernel_timespec *_ts)
return ret;
}
+#ifdef CONFIG_HYPERV_TIMER
+/* This will override the default hv_get_raw_timer() */
+#define hv_get_raw_timer() __arch_counter_get_cntvct()
+#include
+
+extern struct ms_hyperv_tsc_page
+_hvclock_page __attribute__((visibility("hidden")));
+
+static u64 vread_hvclock(void)
+{
+ return hv_read_tsc_page(&_hvclock_page);
+}
+#endif
+
static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
{
u64 res;
@@ -78,6 +92,11 @@ static __always_inline u64 __arch_get_hw_counter(s32
clock_mode)
if (clock_mode == VCLOCK_NONE)
return __VDSO_USE_SYSCALL;
+#ifdef CONFIG_HYPERV_TIMER
+ if (likely(clock_mode == VCLOCK_HVCLOCK))
+ return vread_hvclock();
+#endif
+
/*
* This isb() is required to prevent that the counter value
* is speculated.
--
2.24.0
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