From: "Steve Wise" <swise@opengridcomputing.com>
To: "'Sagi Grimberg'" <sagig@dev.mellanox.co.il>, <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>
References: <20150705231831.12029.80307.stgit@build2.ogc.int> <20150705232158.12029.25472.stgit@build2.ogc.int> <559A3536.3020807@dev.mellanox.co.il>
In-Reply-To: <559A3536.3020807@dev.mellanox.co.il>
Subject: RE: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
Date: Mon, 6 Jul 2015 09:39:12 -0500
Message-ID: <001801d0b7f9$8673a550$935aeff0$@opengridcomputing.com>
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Sender: linux-nfs-owner@vger.kernel.org


> -----Original Message-----
> From: Sagi Grimberg [mailto:sagig@dev.mellanox.co.il]
> Sent: Monday, July 06, 2015 2:59 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));
> > +}
> > +
> > +/**
> > + * rdma_fast_reg_access_flags - Returns the access flags needed for a fast
> > + * register operation.
> > + * @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 for a fast registration
> > + * work request.
> > + *
> > + * Return: the ib_access_flags value needed for fast registration.
> > + */
> > +static inline int rdma_fast_reg_access_flags(struct ib_pd *pd, int roles,
> > +					     int attrs)
> > +{
> > +	return rdma_device_access_flags(pd, roles, attrs);
> > +}
> 
> Why do we have rdma_fast_reg_access_flags() that just trampolines to
> rdma_device_access_flags()? why do we need it?

My initial thought was that fast_reg access flags might be different that general MR access flags for some devices.  But since that isn't the cases, I'll remove it.