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

Steve Wise
2015-07-06T14:39:12Z

> -----Original Message-----
> From: Sagi Grimberg [mailto:sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org]
> Sent: Monday, July 06, 2015 2:59 AM
> To: Steve Wise; dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
> Cc: sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; roid-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; eli-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; target-
> devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org; bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.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-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
> > ---
> >
> > 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.

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