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David Vrabel

2013-May-13 17:56 UTC

[PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

From: David Vrabel <david.vrabel@citrix.com>

All the virtualized platforms (KVM, lguest and Xen) have persistent
wallclocks that have more than one second of precision.

read_persistent_wallclock() and update_persistent_wallclock() allow
for nanosecond precision but their implementation on x86 with
x86_platform.get/set_wallclock() only allows for one second precision.
This means guests may see a wallclock time that is off by up to 1
second.

Make set_wallclock() and get_wallclock() take a struct timespec
parameter (which allows for nanosecond precision) so KVM and Xen
guests may start with a more accurate wallclock time and a Xen dom0
can maintain a more accurate wallclock for guests.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/mc146818rtc.h |    4 ++--
 arch/x86/include/asm/x86_init.h    |    6 ++++--
 arch/x86/kernel/kvmclock.c         |    9 +++------
 arch/x86/kernel/rtc.c              |   17 +++++++----------
 arch/x86/lguest/boot.c             |    4 ++--
 arch/x86/platform/efi/efi.c        |   10 ++++++----
 arch/x86/xen/time.c                |   19 ++++++-------------
 include/linux/efi.h                |    4 ++--
 8 files changed, 32 insertions(+), 41 deletions(-)

diff --git a/arch/x86/include/asm/mc146818rtc.h
b/arch/x86/include/asm/mc146818rtc.h
index d354fb7..a55c7ef 100644
--- a/arch/x86/include/asm/mc146818rtc.h
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -95,8 +95,8 @@ static inline unsigned char current_lock_cmos_reg(void)
 unsigned char rtc_cmos_read(unsigned char addr);
 void rtc_cmos_write(unsigned char val, unsigned char addr);
 
-extern int mach_set_rtc_mmss(unsigned long nowtime);
-extern unsigned long mach_get_cmos_time(void);
+extern int mach_set_rtc_mmss(const struct timespec *now);
+extern void mach_get_cmos_time(struct timespec *now);
 
 #define RTC_IRQ 8
 
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index d8d9922..828a156 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -142,6 +142,8 @@ struct x86_cpuinit_ops {
 	void (*fixup_cpu_id)(struct cpuinfo_x86 *c, int node);
 };
 
+struct timespec;
+
 /**
  * struct x86_platform_ops - platform specific runtime functions
  * @calibrate_tsc:		calibrate TSC
@@ -156,8 +158,8 @@ struct x86_cpuinit_ops {
  */
 struct x86_platform_ops {
 	unsigned long (*calibrate_tsc)(void);
-	unsigned long (*get_wallclock)(void);
-	int (*set_wallclock)(unsigned long nowtime);
+	void (*get_wallclock)(struct timespec *ts);
+	int (*set_wallclock)(const struct timespec *ts);
 	void (*iommu_shutdown)(void);
 	bool (*is_untracked_pat_range)(u64 start, u64 end);
 	void (*nmi_init)(void);
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index d2c3812..0db81ab 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -48,10 +48,9 @@ static struct pvclock_wall_clock wall_clock;
  * have elapsed since the hypervisor wrote the data. So we try to account for
  * that with system time
  */
-static unsigned long kvm_get_wallclock(void)
+static void kvm_get_wallclock(struct timespec *now)
 {
 	struct pvclock_vcpu_time_info *vcpu_time;
-	struct timespec ts;
 	int low, high;
 	int cpu;
 
@@ -64,14 +63,12 @@ static unsigned long kvm_get_wallclock(void)
 	cpu = smp_processor_id();
 
 	vcpu_time = &hv_clock[cpu].pvti;
-	pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
+	pvclock_read_wallclock(&wall_clock, vcpu_time, now);
 
 	preempt_enable();
-
-	return ts.tv_sec;
 }
 
-static int kvm_set_wallclock(unsigned long now)
+static int kvm_set_wallclock(const struct timespec *now)
 {
 	return -1;
 }
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 198eb20..0aa2939 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -38,8 +38,9 @@ EXPORT_SYMBOL(rtc_lock);
  * jump to the next second precisely 500 ms later. Check the Motorola
  * MC146818A or Dallas DS12887 data sheet for details.
  */
-int mach_set_rtc_mmss(unsigned long nowtime)
+int mach_set_rtc_mmss(const struct timespec *now)
 {
+	unsigned long nowtime = now->tv_sec;
 	struct rtc_time tm;
 	int retval = 0;
 
@@ -58,7 +59,7 @@ int mach_set_rtc_mmss(unsigned long nowtime)
 	return retval;
 }
 
-unsigned long mach_get_cmos_time(void)
+void mach_get_cmos_time(struct timespec *now)
 {
 	unsigned int status, year, mon, day, hour, min, sec, century = 0;
 	unsigned long flags;
@@ -107,7 +108,8 @@ unsigned long mach_get_cmos_time(void)
 	} else
 		year += CMOS_YEARS_OFFS;
 
-	return mktime(year, mon, day, hour, min, sec);
+	now->tv_sec = mktime(year, mon, day, hour, min, sec);
+	now->tv_nsec = 0;
 }
 
 /* Routines for accessing the CMOS RAM/RTC. */
@@ -135,18 +137,13 @@ EXPORT_SYMBOL(rtc_cmos_write);
 
 int update_persistent_clock(struct timespec now)
 {
-	return x86_platform.set_wallclock(now.tv_sec);
+	return x86_platform.set_wallclock(&now);
 }
 
 /* not static: needed by APM */
 void read_persistent_clock(struct timespec *ts)
 {
-	unsigned long retval;
-
-	retval = x86_platform.get_wallclock();
-
-	ts->tv_sec = retval;
-	ts->tv_nsec = 0;
+	x86_platform.get_wallclock(ts);
 }
 
 
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 7114c63..8424d5a 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -882,9 +882,9 @@ int lguest_setup_irq(unsigned int irq)
  * It would be far better for everyone if the Guest had its own clock, but
  * until then the Host gives us the time on every interrupt.
  */
-static unsigned long lguest_get_wallclock(void)
+static void lguest_get_wallclock(struct timespec *now)
 {
-	return lguest_data.time.tv_sec;
+	*now = lguest_data.time;
 }
 
 /*
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 55856b2..dd3b825 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -352,8 +352,9 @@ static efi_status_t __init phys_efi_get_time(efi_time_t *tm,
 	return status;
 }
 
-int efi_set_rtc_mmss(unsigned long nowtime)
+int efi_set_rtc_mmss(const struct timespec *now)
 {
+	unsigned long nowtime = now->tv_sec;
 	efi_status_t 	status;
 	efi_time_t 	eft;
 	efi_time_cap_t 	cap;
@@ -388,7 +389,7 @@ int efi_set_rtc_mmss(unsigned long nowtime)
 	return 0;
 }
 
-unsigned long efi_get_time(void)
+void efi_get_time(struct timespec *now)
 {
 	efi_status_t status;
 	efi_time_t eft;
@@ -398,8 +399,9 @@ unsigned long efi_get_time(void)
 	if (status != EFI_SUCCESS)
 		pr_err("Oops: efitime: can''t read time!\n");
 
-	return mktime(eft.year, eft.month, eft.day, eft.hour,
-		      eft.minute, eft.second);
+	now->tv_sec = mktime(eft.year, eft.month, eft.day, eft.hour,
+			     eft.minute, eft.second);
+	now->tv_nsec = 0;
 }
 
 /*
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 3d88bfd..a1947ac 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -191,32 +191,25 @@ static void xen_read_wallclock(struct timespec *ts)
 	put_cpu_var(xen_vcpu);
 }
 
-static unsigned long xen_get_wallclock(void)
+static void xen_get_wallclock(struct timespec *now)
 {
-	struct timespec ts;
-
-	xen_read_wallclock(&ts);
-	return ts.tv_sec;
+	xen_read_wallclock(now);
 }
 
-static int xen_set_wallclock(unsigned long now)
+static int xen_set_wallclock(const struct timespec *now)
 {
 	struct xen_platform_op op;
-	int rc;
 
 	/* do nothing for domU */
 	if (!xen_initial_domain())
 		return -1;
 
 	op.cmd = XENPF_settime;
-	op.u.settime.secs = now;
-	op.u.settime.nsecs = 0;
+	op.u.settime.secs = now->tv_sec;
+	op.u.settime.nsecs = now->tv_nsec;
 	op.u.settime.system_time = xen_clocksource_read();
 
-	rc = HYPERVISOR_dom0_op(&op);
-	WARN(rc != 0, "XENPF_settime failed: now=%ld\n", now);
-
-	return rc;
+	return HYPERVISOR_dom0_op(&op);
 }
 
 static struct clocksource xen_clocksource __read_mostly = {
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 2bc0ad7..0068bba 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -594,8 +594,8 @@ extern u64 efi_mem_attribute (unsigned long phys_addr,
unsigned long size);
 extern int __init efi_uart_console_only (void);
 extern void efi_initialize_iomem_resources(struct resource *code_resource,
 		struct resource *data_resource, struct resource *bss_resource);
-extern unsigned long efi_get_time(void);
-extern int efi_set_rtc_mmss(unsigned long nowtime);
+extern void efi_get_time(struct timespec *now);
+extern int efi_set_rtc_mmss(const struct timespec *now);
 extern void efi_reserve_boot_services(void);
 extern struct efi_memory_map memmap;
 
-- 
1.7.2.5

John Stultz

2013-May-14 00:57 UTC

head link

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

On 05/13/2013 10:56 AM, David Vrabel wrote:> From: David Vrabel <david.vrabel@citrix.com>
>
> All the virtualized platforms (KVM, lguest and Xen) have persistent
> wallclocks that have more than one second of precision.
>
> read_persistent_wallclock() and update_persistent_wallclock() allow
> for nanosecond precision but their implementation on x86 with
> x86_platform.get/set_wallclock() only allows for one second precision.
> This means guests may see a wallclock time that is off by up to 1
> second.
>
> Make set_wallclock() and get_wallclock() take a struct timespec
> parameter (which allows for nanosecond precision) so KVM and Xen
> guests may start with a more accurate wallclock time and a Xen dom0
> can maintain a more accurate wallclock for guests.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This one looks pretty good.
Lets circle around on the other two and if after that they still don''t 
make sense, I''ll just queue this one.

Sorry if I''m being thick headed.

thanks
-john

John Stultz

2013-May-14 17:52 UTC

head link

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

On 05/13/2013 10:56 AM, David Vrabel wrote:> From: David Vrabel <david.vrabel@citrix.com>
>
> All the virtualized platforms (KVM, lguest and Xen) have persistent
> wallclocks that have more than one second of precision.
>
> read_persistent_wallclock() and update_persistent_wallclock() allow
> for nanosecond precision but their implementation on x86 with
> x86_platform.get/set_wallclock() only allows for one second precision.
> This means guests may see a wallclock time that is off by up to 1
> second.
>
> Make set_wallclock() and get_wallclock() take a struct timespec
> parameter (which allows for nanosecond precision) so KVM and Xen
> guests may start with a more accurate wallclock time and a Xen dom0
> can maintain a more accurate wallclock for guests.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
I''ve gone ahead and queued this one for 3.11

thanks
-john

John Stultz

2013-May-29 00:18 UTC

head link

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

On 05/13/2013 10:56 AM, David Vrabel wrote:> From: David Vrabel <david.vrabel@citrix.com>
>
> All the virtualized platforms (KVM, lguest and Xen) have persistent
> wallclocks that have more than one second of precision.
>
> read_persistent_wallclock() and update_persistent_wallclock() allow
> for nanosecond precision but their implementation on x86 with
> x86_platform.get/set_wallclock() only allows for one second precision.
> This means guests may see a wallclock time that is off by up to 1
> second.
>
> Make set_wallclock() and get_wallclock() take a struct timespec
> parameter (which allows for nanosecond precision) so KVM and Xen
> guests may start with a more accurate wallclock time and a Xen dom0
> can maintain a more accurate wallclock for guests.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> ---
>   arch/x86/include/asm/mc146818rtc.h |    4 ++--
>   arch/x86/include/asm/x86_init.h    |    6 ++++--
>   arch/x86/kernel/kvmclock.c         |    9 +++------
>   arch/x86/kernel/rtc.c              |   17 +++++++----------
>   arch/x86/lguest/boot.c             |    4 ++--
>   arch/x86/platform/efi/efi.c        |   10 ++++++----
>   arch/x86/xen/time.c                |   19 ++++++-------------
>   include/linux/efi.h                |    4 ++--
Just FYI, David: You missed the vrtc code with this conversion.

I finally got around to pushing my current queue to my public tree and 
the kbuild robot noticed the build failure (required INTEL_MID config to 
trigger).

The fix I''ve queued is here:
https://git.linaro.org/gitweb?p=people/jstultz/linux.git;a=commitdiff;h=52d8e9cc6718ae9e6c44b7723028e4717ba91c8b;hp=1dd5234774b33a17743ae62e8b46b5cd0059e1c7

Let me know if you have any objection or comments on this.

thanks
-john

David Vrabel

2013-May-29 12:16 UTC

head link

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

On 29/05/13 01:18, John Stultz wrote:> On 05/13/2013 10:56 AM, David Vrabel wrote:
>> From: David Vrabel <david.vrabel@citrix.com>
>>
>> All the virtualized platforms (KVM, lguest and Xen) have persistent
>> wallclocks that have more than one second of precision.
>>
>> read_persistent_wallclock() and update_persistent_wallclock() allow
>> for nanosecond precision but their implementation on x86 with
>> x86_platform.get/set_wallclock() only allows for one second precision.
>> This means guests may see a wallclock time that is off by up to 1
>> second.
>>
>> Make set_wallclock() and get_wallclock() take a struct timespec
>> parameter (which allows for nanosecond precision) so KVM and Xen
>> guests may start with a more accurate wallclock time and a Xen dom0
>> can maintain a more accurate wallclock for guests.
>>
>> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
>> ---
>>   arch/x86/include/asm/mc146818rtc.h |    4 ++--
>>   arch/x86/include/asm/x86_init.h    |    6 ++++--
>>   arch/x86/kernel/kvmclock.c         |    9 +++------
>>   arch/x86/kernel/rtc.c              |   17 +++++++----------
>>   arch/x86/lguest/boot.c             |    4 ++--
>>   arch/x86/platform/efi/efi.c        |   10 ++++++----
>>   arch/x86/xen/time.c                |   19 ++++++-------------
>>   include/linux/efi.h                |    4 ++--
> 
> Just FYI, David: You missed the vrtc code with this conversion.
> 
> I finally got around to pushing my current queue to my public tree and
> the kbuild robot noticed the build failure (required INTEL_MID config to
> trigger).
> 
> The fix I''ve queued is here:
>
https://git.linaro.org/gitweb?p=people/jstultz/linux.git;a=commitdiff;h=52d8e9cc6718ae9e6c44b7723028e4717ba91c8b;hp=1dd5234774b33a17743ae62e8b46b5cd0059e1c7
Oops. Sorry about that.  That fix looks fine.

David

Xen devel - May 2013 - [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

[PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()

Re: [PATCH 1/3] x86: increase precision of x86_platform.get/set_wallclock()