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


> -----Original Message-----
> From: Greg KH [mailto:gregkh@linuxfoundation.org]
> Sent: Thursday, January 19, 2017 4:59 AM
> To: KY Srinivasan <kys@microsoft.com>
> Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org;
> olaf@aepfle.de; apw@canonical.com; vkuznets@redhat.com;
> jasowang@redhat.com; leann.ogasawara@canonical.com
> 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@exchange.microsoft.com
> wrote:
> > From: K. Y. Srinivasan <kys@microsoft.com>
> >
> > 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@microsoft.com>
> > ---
> > 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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