Re: [dpdk-dev] [EXT] Re: [PATCH v2 1/6] eal/interrupts: implement get set APIs

[Harman Kalra <hkalra@marvell.com>]

Hi Dmitry,

Thanks for your inputs.
Please see inline.

> -----Original Message-----
> From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> Sent: Thursday, October 14, 2021 6:29 AM
> To: Harman Kalra <hkalra@marvell.com>
> Cc: dev@dpdk.org; Thomas Monjalon <thomas@monjalon.net>; Ray Kinsella
> <mdr@ashroe.eu>; david.marchand@redhat.com
> Subject: [EXT] Re: [PATCH v2 1/6] eal/interrupts: implement get set APIs
> 
> External Email
> 
> ----------------------------------------------------------------------
> 2021-10-05 17:44 (UTC+0530), Harman Kalra:
> > [...]
> > +int rte_intr_instance_copy(struct rte_intr_handle *intr_handle,
> > +			   const struct rte_intr_handle *src) {
> > +	if (intr_handle == NULL) {
> > +		RTE_LOG(ERR, EAL, "Interrupt instance unallocated\n");
> > +		rte_errno = ENOTSUP;
> > +		goto fail;
> > +	}
> > +
> > +	if (src == NULL) {
> > +		RTE_LOG(ERR, EAL, "Source interrupt instance
> unallocated\n");
> > +		rte_errno = EINVAL;
> > +		goto fail;
> > +	}
> > +
> > +	intr_handle->fd = src->fd;
> > +	intr_handle->vfio_dev_fd = src->vfio_dev_fd;
> > +	intr_handle->type = src->type;
> > +	intr_handle->max_intr = src->max_intr;
> > +	intr_handle->nb_efd = src->nb_efd;
> > +	intr_handle->efd_counter_size = src->efd_counter_size;
> > +
> > +	memcpy(intr_handle->efds, src->efds, src->nb_intr);
> > +	memcpy(intr_handle->elist, src->elist, src->nb_intr);
> 
> Buffer overrun if "intr_handle->nb_intr < src->nb_intr"?

Ack, I will add the check.

> 
> > +
> > +	return 0;
> > +fail:
> > +	return -rte_errno;
> > +}
> > +
> > +int rte_intr_instance_mem_allocator_get(
> > +				const struct rte_intr_handle *intr_handle) {
> > +	if (intr_handle == NULL) {
> > +		RTE_LOG(ERR, EAL, "Interrupt instance unallocated\n");
> > +		return -ENOTSUP;
> 
> ENOTSUP usually means the operation is valid from API standpoint but not
> supported by the implementation. EINVAL/EFAULT suits better.

Ack, will make it EFAULT.

> 
> > +	}
> > +
> > +	return intr_handle->mem_allocator;
> > +}
> 
> What do you think about having an API to retrieve the entire flags instead?

Now since we are planning to remove this flag variable and rely on auto detection mechanism.
I will remove this API.


> 
> > +
> > +void rte_intr_instance_free(struct rte_intr_handle *intr_handle) {
> > +	if (intr_handle == NULL) {
> > +		RTE_LOG(ERR, EAL, "Interrupt instance unallocated\n");
> > +		rte_errno = ENOTSUP;
> > +	}
> 
> API are neater when free(NULL) is a no-op.

Correct.

> 
> > +
> > +	if (intr_handle->mem_allocator)
> > +		rte_free(intr_handle);
> > +	else
> > +		free(intr_handle);
> > +}
> > +
> > +int rte_intr_fd_set(struct rte_intr_handle *intr_handle, int fd) {
> > +	if (intr_handle == NULL) {
> > +		RTE_LOG(ERR, EAL, "Interrupt instance unallocated\n");
> > +		rte_errno = ENOTSUP;
> > +		goto fail;
> > +	}
> 
> This piece repeats over and over, how about making it a function or a macro,
> like in ethdev?

Ack, will define a macro for the same.

> 
> > +
> > +	intr_handle->fd = fd;
> > +
> > +	return 0;
> > +fail:
> > +	return -rte_errno;
> > +}
> > +
> > +int rte_intr_fd_get(const struct rte_intr_handle *intr_handle) {
> > +	if (intr_handle == NULL) {
> > +		RTE_LOG(ERR, EAL, "Interrupt instance unallocated\n");
> > +		rte_errno = ENOTSUP;
> > +		goto fail;
> > +	}
> > +
> > +	return intr_handle->fd;
> > +fail:
> > +	return -1;
> > +}
> 
> Please add a similar pair of experimental API for the "handle" member, it is
> needed for Windows interrupt support I'm working on top of these series
> (IIUC, API changes should be closed by RC1.) If you will be doing this and
> don't like "handle" name, it might be like "dev_handle" or
> "windows_device".

I add new APIs to get/set handle. Let's rename it to "windows_handle"


> 
> > [...]
> > +int rte_intr_max_intr_set(struct rte_intr_handle *intr_handle,
> > +				 int max_intr)
> > +{
> > +	if (intr_handle == NULL) {
> > +		RTE_LOG(ERR, EAL, "Interrupt instance unallocated\n");
> > +		rte_errno = ENOTSUP;
> > +		goto fail;
> > +	}
> > +
> > +	if (max_intr > intr_handle->nb_intr) {
> > +		RTE_LOG(ERR, EAL, "Max_intr=%d greater than
> > +RTE_MAX_RXTX_INTR_VEC_ID=%d",
> 
> The macros is not used in the comparison, neither should the log mention it.

I will add the check.


> 
> > [...]
> > @@ -420,6 +412,14 @@ EXPERIMENTAL {
> >
> >  	# added in 21.08
> >  	rte_power_monitor_multi; # WINDOWS_NO_EXPORT
> > +
> > +	# added in 21.11
> > +	rte_intr_fd_set;
> > +	rte_intr_fd_get;
> 
> WINDOWS_NO_EXPORT

Ack.

> 
> > +	rte_intr_type_set;
> > +	rte_intr_type_get;
> > +	rte_intr_instance_alloc;
> > +	rte_intr_instance_free;
> >  };
> 
> Do I understand correctly that these exports are needed to allow an
> application to use DPDK callback facilities for its own interrupt sources?

I exported only those APIs which are currently used by test suite or example
applications, may be later more APIs can be moved from internal to public on
need basis.


> If so, I'd suggest that instead we export a simpler set of functions:
> 1. Create/free a handle instance with automatic fixed type selection.
> 2. Trigger an interrupt on the specified handle instance.
> The flow would be that the application listens on whatever it wants, probably
> with OS-specific mechanisms, and just notifies the interrupt thread about
> events to trigger callbacks.
> Because these APIs are experimental we don't need to change it now, just my
> thoughts for the future.

I am sorry but I did not followed your suggestion, can you please explain.

Thanks
Harman