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

["Steve Wise" <swise@opengridcomputing.com>]

> -----Original Message-----
> From: linux-rdma-owner@vger.kernel.org [mailto:linux-rdma-owner@vger.kernel.org] On Behalf Of Sagi Grimberg
> Sent: Monday, July 06, 2015 11:18 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 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.
> 

So just export rdma_device_access_flags(rd, roles, attrs), and then change the ULPs to call this to obtain the access flags.  That is ok with me.  What do others think?