RE: [PATCH V2 05/18] Drivers: hv: vmbus: Consolidate all Hyper-V specific clocksource code

[KY Srinivasan <kys@xxxxxxxxxxxxx>]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Thursday, January 19, 2017 4:59 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx;
> olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx;
> jasowang@xxxxxxxxxx; leann.ogasawara@xxxxxxxxxxxxx
> Subject: Re: [PATCH V2 05/18] Drivers: hv: vmbus: Consolidate all Hyper-V
> specific clocksource code
> 
> On Wed, Jan 18, 2017 at 04:45:04PM -0700, kys@xxxxxxxxxxxxxxxxxxxxxx
> wrote:
> > From: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> >
> > As part of the effort to separate out architecture specific code,
> > consolidate all Hyper-V specific clocksource code to an architecture
> > specific code.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > ---
> >  arch/x86/hyperv/hv_init.c       |  104
> +++++++++++++++++++++++++++++++++++++++
> >  arch/x86/include/asm/mshyperv.h |   12 +++++
> >  arch/x86/kernel/cpu/mshyperv.c  |   23 ---------
> >  drivers/hv/hv.c                 |   95 -----------------------------------
> >  drivers/hv/hyperv_vmbus.h       |    8 ---
> >  5 files changed, 116 insertions(+), 126 deletions(-)
> >
> > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> > index b5c8e04..691dfaf 100644
> > --- a/arch/x86/hyperv/hv_init.c
> > +++ b/arch/x86/hyperv/hv_init.c
> > @@ -24,6 +24,79 @@
> >  #include <linux/version.h>
> >  #include <linux/vmalloc.h>
> >  #include <linux/mm.h>
> > +#include <linux/clockchips.h>
> > +
> > +
> > +#ifdef CONFIG_X86_64
> > +
> > +static struct ms_hyperv_tsc_page *tsc_pg;
> > +
> > +static u64 read_hv_clock_tsc(struct clocksource *arg)
> > +{
> > +	u64 current_tick;
> > +
> > +	if (tsc_pg->tsc_sequence != 0) {
> > +		/*
> > +		 * Use the tsc page to compute the value.
> > +		 */
> > +
> > +		while (1) {
> > +			u64 tmp;
> > +			u32 sequence = tsc_pg->tsc_sequence;
> > +			u64 cur_tsc;
> > +			u64 scale = tsc_pg->tsc_scale;
> > +			s64 offset = tsc_pg->tsc_offset;
> > +
> > +			rdtscll(cur_tsc);
> > +			/* current_tick = ((cur_tsc *scale) >> 64) + offset */
> > +			asm("mulq %3"
> > +				: "=d" (current_tick), "=a" (tmp)
> > +				: "a" (cur_tsc), "r" (scale));
> > +
> > +			current_tick += offset;
> > +			if (tsc_pg->tsc_sequence == sequence)
> > +				return current_tick;
> > +
> > +			if (tsc_pg->tsc_sequence != 0)
> > +				continue;
> > +			/*
> > +			 * Fallback using MSR method.
> > +			 */
> > +			break;
> > +		}
> > +	}
> > +	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> > +	return current_tick;
> > +}
> > +
> > +static struct clocksource hyperv_cs_tsc = {
> > +		.name		= "hyperv_clocksource_tsc_page",
> > +		.rating		= 400,
> > +		.read		= read_hv_clock_tsc,
> > +		.mask		= CLOCKSOURCE_MASK(64),
> > +		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
> > +};
> > +#endif
> > +
> > +static u64 read_hv_clock_msr(struct clocksource *arg)
> > +{
> > +	u64 current_tick;
> > +	/*
> > +	 * Read the partition counter to get the current tick count. This count
> > +	 * is set to 0 when the partition is created and is incremented in
> > +	 * 100 nanosecond units.
> > +	 */
> > +	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> > +	return current_tick;
> > +}
> > +
> > +static struct clocksource hyperv_cs_msr = {
> > +	.name		= "hyperv_clocksource_msr",
> > +	.rating		= 400,
> > +	.read		= read_hv_clock_msr,
> > +	.mask		= CLOCKSOURCE_MASK(64),
> > +	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
> > +};
> >
> >  static void *hypercall_pg;
> >  /*
> > @@ -31,6 +104,7 @@
> >   * hypervisor has been detected.
> >   *
> >   * 1. Setup the hypercall page.
> > + * 2. Register Hyper-V specific clocksource.
> >   */
> >  void hyperv_init(void)
> >  {
> > @@ -58,6 +132,36 @@ void hyperv_init(void)
> >  	hypercall_msr.enable = 1;
> >  	hypercall_msr.guest_physical_address =
> vmalloc_to_pfn(hypercall_pg);
> >  	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> > +
> > +	/*
> > +	 * Register Hyper-V specific clocksource.
> > +	 */
> > +#ifdef CONFIG_X86_64
> > +	if (ms_hyperv.features &
> HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
> > +		union hv_x64_msr_hypercall_contents tsc_msr;
> > +
> > +		tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL,
> PAGE_KERNEL);
> > +		if (!tsc_pg)
> > +			clocksource_register_hz(&hyperv_cs_msr,
> NSEC_PER_SEC/100);
> > +			return;
> 
> There's a reason you always test-build your patches and pay attention to
> the warnings!
> 
> How did this pass your tests?
> 
> I've stopped applying patches here.

Greg,

Thank you for spotting the issue; I will fix the problem and resend.

K. Y
> 
> greg k-h
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