Re: [PATCH V2] x86/Hyper-V: don't allocate clockevent device when synthetic timer is unavailable

[Tianyu Lan]

On 3/31/2020 7:20 PM, Vitaly Kuznetsov wrote:
> ltykernel@xxxxxxxxx writes:
>
> > From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> >
> > Current code initializes clock event data structure for syn timer
> > even when it's unavailable. Fix it.
> >
> > Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> > ---
> > Change since v1:
> > 	Update title and commit log.
> >
> >   drivers/hv/hv.c | 15 +++++++++------
> >   1 file changed, 9 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> > index 632d25674e7f..2e893768fc76 100644
> > --- a/drivers/hv/hv.c
> > +++ b/drivers/hv/hv.c
> > @@ -212,13 +212,16 @@ int hv_synic_alloc(void)
> >   		tasklet_init(&hv_cpu->msg_dpc,
> >   			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
> >   
> > -		hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
> > -					  GFP_KERNEL);
> > -		if (hv_cpu->clk_evt == NULL) {
> > -			pr_err("Unable to allocate clock event device\n");
> > -			goto err;
> > +		if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
> > +			hv_cpu->clk_evt =
> > +				kzalloc(sizeof(struct clock_event_device),
> > +						  GFP_KERNEL);
> > +			if (hv_cpu->clk_evt == NULL) {
> > +				pr_err("Unable to allocate clock event device\n");
> > +				goto err;
> > +			}
> > +			hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
> >   		}
> > -		hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
> >   
> >   		hv_cpu->synic_message_page =
> >   			(void *)get_zeroed_page(GFP_ATOMIC);
>
> Thank you for fixing the subject! I had one more question on the
> previous version which still stands: which tree is this patch for?
> Upstream, clockevent allocation has moved to
> drivers/clocksource/hyperv_timer.c and the code there is different.
Yes, I just noticed I fixed an issue on the old code after Michael 
reminded me. Sorry for noise. Please ignore it.