RE: [PATCH RESEND 09/27] drivers:hv: Export the API to invoke a hypercall on Hyper-V

[KY Srinivasan]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Monday, December 14, 2015 7:08 PM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx;
> olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx;
> jasowang@xxxxxxxxxx; Jake Oshins <jakeo@xxxxxxxxxxxxx>
> Subject: Re: [PATCH RESEND 09/27] drivers:hv: Export the API to invoke a
> hypercall on Hyper-V
> 
> On Mon, Dec 14, 2015 at 04:01:40PM -0800, K. Y. Srinivasan wrote:
> > From: Jake Oshins <jakeo@xxxxxxxxxxxxx>
> >
> > This patch exposes the function that hv_vmbus.ko uses to make hypercalls.
> This
> > is necessary for retargeting an interrupt when it is given a new affinity.
> >
> > Since we are exporting this API, rename the API as it will be visible outside
> > the hv.c file.
> >
> > Signed-off-by: Jake Oshins <jakeo@xxxxxxxxxxxxx>
> > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > ---
> >  drivers/hv/hv.c           |   20 ++++++++++----------
> >  drivers/hv/hyperv_vmbus.h |    2 +-
> >  include/linux/hyperv.h    |    1 +
> >  3 files changed, 12 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> > index 6341be8..7a06933 100644
> > --- a/drivers/hv/hv.c
> > +++ b/drivers/hv/hv.c
> > @@ -89,9 +89,9 @@ static int query_hypervisor_info(void)
> >  }
> >
> >  /*
> > - * do_hypercall- Invoke the specified hypercall
> > + * hv_do_hypercall- Invoke the specified hypercall
> >   */
> > -static u64 do_hypercall(u64 control, void *input, void *output)
> > +u64 hv_do_hypercall(u64 control, void *input, void *output)
> >  {
> >  	u64 input_address = (input) ? virt_to_phys(input) : 0;
> >  	u64 output_address = (output) ? virt_to_phys(output) : 0;
> > @@ -132,6 +132,7 @@ static u64 do_hypercall(u64 control, void *input,
> void *output)
> >  	return hv_status_lo | ((u64)hv_status_hi << 32);
> >  #endif /* !x86_64 */
> >  }
> > +EXPORT_SYMBOL_GPL(hv_do_hypercall);
> >
> >  #ifdef CONFIG_X86_64
> >  static cycle_t read_hv_clock_tsc(struct clocksource *arg)
> > @@ -315,7 +316,7 @@ int hv_post_message(union hv_connection_id
> connection_id,
> >  {
> >
> >  	struct hv_input_post_message *aligned_msg;
> > -	u16 status;
> > +	u64 status;
> >
> >  	if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
> >  		return -EMSGSIZE;
> > @@ -329,11 +330,10 @@ int hv_post_message(union hv_connection_id
> connection_id,
> >  	aligned_msg->payload_size = payload_size;
> >  	memcpy((void *)aligned_msg->payload, payload, payload_size);
> >
> > -	status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
> > -		& 0xFFFF;
> > +	status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg,
> NULL);
> >
> >  	put_cpu();
> > -	return status;
> > +	return status & 0xFFFF;
> >  }
> >
> >
> > @@ -343,13 +343,13 @@ int hv_post_message(union hv_connection_id
> connection_id,
> >   *
> >   * This involves a hypercall.
> >   */
> > -u16 hv_signal_event(void *con_id)
> > +int hv_signal_event(void *con_id)
> >  {
> > -	u16 status;
> > +	u64 status;
> >
> > -	status = (do_hypercall(HVCALL_SIGNAL_EVENT, con_id, NULL) &
> 0xFFFF);
> > +	status = hv_do_hypercall(HVCALL_SIGNAL_EVENT, con_id, NULL);
> >
> > -	return status;
> > +	return status & 0xFFFF;
> 
> This "feels" odd, as the return value isn't the traditional 0 or -ERROR,
> right?  Why are you masking off the top bits?
> 
> And, no one ever does anything with the return value of
> hv_signal_event(), so why have it return anything anyway?
> 
> I'll take this, but please fix up the area, it's messy...

Thanks Greg. Will do.

K. Y
> 
> greg k-h
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