Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags

[Sagi Grimberg <sagig@dev.mellanox.co.il>]

On 7/6/2015 5:37 PM, Steve Wise wrote:
>
>
>> -----Original Message-----
>> From: Sagi Grimberg [mailto:sagig@dev.mellanox.co.il]
>> Sent: Monday, July 06, 2015 2:54 AM
>> To: Steve Wise; dledford@redhat.com
>> Cc: sagig@mellanox.com; ogerlitz@mellanox.com; roid@mellanox.com; linux-rdma@vger.kernel.org; eli@mellanox.com; target-
>> devel@vger.kernel.org; linux-nfs@vger.kernel.org; trond.myklebust@primarydata.com; bfields@fieldses.org
>> Subject: Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
>>
>> On 7/6/2015 2:22 AM, Steve Wise wrote:
>>> The semantics for MR access flags are not consistent across RDMA
>>> protocols.  So rather than have applications try and glean what they
>>> need, have them pass in the intended roles and attributes for the MR to
>>> be allocated and let the RDMA core select the appropriate access flags
>>> given the roles, attributes, and device capabilities.
>>>
>>> We introduce rdma_mr_roles and rdma_mr_attributes that enumerate the
>>> possible roles and attributes for a MR.  These are documented in the
>>> enums themselves.
>>>
>>> New services exported:
>>>
>>> rdma_device_access_flags() - given the intended MR roles and attributes
>>> passed in, return the ib_access_flags bits for the device.
>>>
>>> rdma_get_dma_mr() - allocate a dma mr using the applications intended
>>> MR roles and MR attributes.  This uses rdma_device_access_flags().
>>>
>>> rdma_fast_reg_access_flags() - return the ib_access_flags bits needed
>>> for a fast register WR given the applications intended MR roles and
>>> MR attributes.  This uses rdma_device_access_flags().
>>>
>>> Signed-off-by: Steve Wise <swise@opengridcomputing.com>
>>> ---
>>>
>>>    drivers/infiniband/core/verbs.c |   30 +++++++++++
>>>    include/rdma/ib_verbs.h         |  106 +++++++++++++++++++++++++++++++++++++++
>>>    2 files changed, 136 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
>>> index bac3fb4..f42595c 100644
>>> --- a/drivers/infiniband/core/verbs.c
>>> +++ b/drivers/infiniband/core/verbs.c
>>> @@ -1144,6 +1144,36 @@ struct ib_mr *ib_get_dma_mr(struct ib_pd *pd, int mr_access_flags)
>>>    }
>>>    EXPORT_SYMBOL(ib_get_dma_mr);
>>>
>>> +int rdma_device_access_flags(struct ib_pd *pd, int roles, int attrs)
>>> +{
>>> +	int access_flags = attrs;
>>> +
>>> +	if (roles & RDMA_MRR_RECV)
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE;
>>> +
>>> +	if (roles & RDMA_MRR_WRITE_DEST)
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_WRITE;
>>> +
>>> +	if (roles & RDMA_MRR_READ_DEST) {
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE;
>>> +		if (rdma_protocol_iwarp(pd->device,
>>> +					rdma_start_port(pd->device)))
>>> +			access_flags |= IB_ACCESS_REMOTE_WRITE;
>>> +	}
>>> +
>>> +	if (roles & RDMA_MRR_READ_SOURCE)
>>> +		access_flags |= IB_ACCESS_REMOTE_READ;
>>> +
>>> +	if (roles & RDMA_MRR_ATOMIC_DEST)
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_ATOMIC;
>>> +
>>> +	if (roles & RDMA_MRR_MW_BIND)
>>> +		access_flags |= IB_ACCESS_MW_BIND;
>>> +
>>> +	return access_flags;
>>> +}
>>> +EXPORT_SYMBOL(rdma_device_access_flags);
>>> +
>>>    struct ib_mr *ib_reg_phys_mr(struct ib_pd *pd,
>>>    			     struct ib_phys_buf *phys_buf_array,
>>>    			     int num_phys_buf,
>>> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
>>> index 986fddb..da1eadf 100644
>>> --- a/include/rdma/ib_verbs.h
>>> +++ b/include/rdma/ib_verbs.h
>>> @@ -2494,6 +2494,112 @@ static inline int ib_req_ncomp_notif(struct ib_cq *cq, int wc_cnt)
>>>    struct ib_mr *ib_get_dma_mr(struct ib_pd *pd, int mr_access_flags);
>>>
>>>    /**
>>> + * rdma_mr_roles - possible roles an RDMA MR will be used for
>>> + *
>>> + * This allows a transport independent RDMA application to
>>> + * create MRs that are usable for all the desired roles w/o
>>> + * having to understand which access rights are needed.
>>> + */
>>> +enum {
>>> +
>>> +	/* lkey used in a ib_recv_wr sge */
>>> +	RDMA_MRR_RECV			= 1,
>>> +
>>> +	/* lkey used for IB_WR_SEND* ops in the ib_send_wr sge */
>>> +	RDMA_MRR_SEND			= (1<<1),
>>> +
>>> +	/* rkey used for IB_WR_RDMA_READ* ops in ib_send_wr wr.rdma.rkey */
>>> +	RDMA_MRR_READ_SOURCE		= (1<<2),
>>> +
>>> +	/* lkey used for IB_WR_RDMA_READ* ops in the ib_send_wr sge */
>>> +	RDMA_MRR_READ_DEST		= (1<<3),
>>> +
>>> +	/* lkey used for IB_WR_RDMA_WRITE* ops in the ib_send_wr sge */
>>> +	RDMA_MRR_WRITE_SOURCE		= (1<<4),
>>> +
>>> +	/* rkey used for IB_WR_RDMA_WRITE* ops in ib_send_wr wr.rdma.rkey */
>>> +	RDMA_MRR_WRITE_DEST		= (1<<5),
>>> +
>>> +	/*
>>> +	 * lkey used for IB_WR_ATOMIC/MASKED_ATOMIC* ops in the ib_send_wr sge
>>> +	 */
>>> +	RDMA_MRR_ATOMIC_SOURCE		= (1<<6),
>>> +
>>> +	/*
>>> +	 * rkey used for IB_WR_ATOMIC/MASKED_ATOMIC* ops in ib_send_wr
>>> +	 * wr.atomic.rkey
>>> +	 */
>>> +	RDMA_MRR_ATOMIC_DEST		= (1<<7),
>>> +
>>> +	/* MR used for a IB_WR_MW_BIND in ib_send_wr wr.bind_mw.bind_info.mr */
>>> +	RDMA_MRR_MW_BIND		= (1<<8),
>>> +};
>>> +
>>> +/**
>>> + * rdma_mr_attributes - attributes for rdma memory regions
>>> + */
>>> +enum {
>>> +	RDMA_MRA_ZERO_BASED		= IB_ZERO_BASED,
>>> +	RDMA_MRA_ACCESS_ON_DEMAND	= IB_ACCESS_ON_DEMAND,
>>> +};
>>> +
>>> +/**
>>> + * rdma_device_access_flags - Returns the device-specific MR access flags.
>>> + * @pd: The protection domain associated with the memory region.
>>> + * @roles: The intended roles of the MR
>>> + * @attrs: The desired attributes of the MR
>>> + *
>>> + * Use the intended roles from @roles along with @attrs and the device
>>> + * capabilities to generate the needed access rights.
>>> + *
>>> + * Return: the ib_access_flags value needed to allocate the MR.
>>> + */
>>> +int rdma_device_access_flags(struct ib_pd *pd, int roles, int attrs);
>>> +
>>> +/**
>>> + * rdma_get_dma_mr - Returns a memory region for system memory that is
>>> + * usable for DMA.
>>> + * @pd: The protection domain associated with the memory region.
>>> + * @roles: The intended roles of the MR
>>> + * @attrs: The desired attributes of the MR
>>> + *
>>> + * Use the intended roles from @roles along with @attrs and the device
>>> + * capabilities to define the needed access rights, and call
>>> + * ib_get_dma_mr() to allocate the MR.
>>> + *
>>> + * Note that the ib_dma_*() functions defined below must be used
>>> + * to create/destroy addresses used with the Lkey or Rkey returned
>>> + * by ib_get_dma_mr().
>>> + *
>>> + * Return: struct ib_mr pointer upon success, or a pointer encoded errno upon
>>> + * failure.
>>> + */
>>> +static inline struct ib_mr *rdma_get_dma_mr(struct ib_pd *pd, int roles,
>>> +					    int attrs)
>>> +{
>>> +	return ib_get_dma_mr(pd, rdma_device_access_flags(pd, roles, attrs));
>>> +}
>>> +
>>
>> I still think this wrapper should go away...
>
> Ok. I'll remove all uses of ib_get_dma_mr()...
>
>

I meant that rdma_get_dma_mr can go away. I'd prefer to get the
needed access_flags and just call existing verb.

Sagi.