-----"Jason Gunthorpe" <jgg@xxxxxxxx> wrote: -----
>To: "Bernard Metzler" <bmt@xxxxxxxxxxxxxx>
>From: "Jason Gunthorpe" <jgg@xxxxxxxx>
>Date: 08/06/2019 02:10PM
>Cc: linux-rdma@xxxxxxxxxxxxxxx
>Subject: [EXTERNAL] Re: [PATCH 1/1] Make user mmapped CQ arming flags
>field 32 bit size to remove 64 bit architecture dependency of siw.
>
>On Mon, Aug 05, 2019 at 04:17:08PM +0200, Bernard Metzler wrote:
>> Signed-off-by: Bernard Metzler <bmt@xxxxxxxxxxxxxx>
>> ---
>
>Don't send patches with empty commit messages. Every patch must have
>a
>comprehensive commit message from now on.
Sorry about this. As Doug pointed out - I sent an extra
cover letter.
>
>> drivers/infiniband/sw/siw/Kconfig | 2 +-
>> drivers/infiniband/sw/siw/siw.h | 2 +-
>> drivers/infiniband/sw/siw/siw_qp.c | 14 ++++++++++----
>> drivers/infiniband/sw/siw/siw_verbs.c | 16 +++++++++++-----
>> include/uapi/rdma/siw-abi.h | 3 ++-
>> 5 files changed, 25 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/infiniband/sw/siw/Kconfig
>b/drivers/infiniband/sw/siw/Kconfig
>> index dace276aea14..b622fc62f2cd 100644
>> --- a/drivers/infiniband/sw/siw/Kconfig
>> +++ b/drivers/infiniband/sw/siw/Kconfig
>> @@ -1,6 +1,6 @@
>> config RDMA_SIW
>> tristate "Software RDMA over TCP/IP (iWARP) driver"
>> - depends on INET && INFINIBAND && LIBCRC32C && 64BIT
>> + depends on INET && INFINIBAND && LIBCRC32C
>> select DMA_VIRT_OPS
>> help
>> This driver implements the iWARP RDMA transport over
>> diff --git a/drivers/infiniband/sw/siw/siw.h
>b/drivers/infiniband/sw/siw/siw.h
>> index 03fd7b2f595f..77b1aabf6ff3 100644
>> --- a/drivers/infiniband/sw/siw/siw.h
>> +++ b/drivers/infiniband/sw/siw/siw.h
>> @@ -214,7 +214,7 @@ struct siw_wqe {
>> struct siw_cq {
>> struct ib_cq base_cq;
>> spinlock_t lock;
>> - u64 *notify;
>> + struct siw_cq_ctrl *notify;
>> struct siw_cqe *queue;
>> u32 cq_put;
>> u32 cq_get;
>> diff --git a/drivers/infiniband/sw/siw/siw_qp.c
>b/drivers/infiniband/sw/siw/siw_qp.c
>> index e27bd5b35b96..0990307c5d2c 100644
>> --- a/drivers/infiniband/sw/siw/siw_qp.c
>> +++ b/drivers/infiniband/sw/siw/siw_qp.c
>> @@ -1013,18 +1013,24 @@ int siw_activate_tx(struct siw_qp *qp)
>> */
>> static bool siw_cq_notify_now(struct siw_cq *cq, u32 flags)
>> {
>> - u64 cq_notify;
>> + u32 cq_notify;
>>
>> if (!cq->base_cq.comp_handler)
>> return false;
>>
>> - cq_notify = READ_ONCE(*cq->notify);
>> + /* Read application shared notification state */
>> + cq_notify = READ_ONCE(cq->notify->flags);
>>
>> if ((cq_notify & SIW_NOTIFY_NEXT_COMPLETION) ||
>> ((cq_notify & SIW_NOTIFY_SOLICITED) &&
>> (flags & SIW_WQE_SOLICITED))) {
>> - /* dis-arm CQ */
>> - smp_store_mb(*cq->notify, SIW_NOTIFY_NOT);
>> + /*
>> + * CQ notification is one-shot: Since the
>> + * current CQE causes user notification,
>> + * the CQ gets dis-aremd and must be re-aremd
>> + * by the user for a new notification.
>> + */
>> + WRITE_ONCE(cq->notify->flags, SIW_NOTIFY_NOT);
>>
>> return true;
>> }
>> diff --git a/drivers/infiniband/sw/siw/siw_verbs.c
>b/drivers/infiniband/sw/siw/siw_verbs.c
>> index 32dc79d0e898..e7f3a2379d9d 100644
>> --- a/drivers/infiniband/sw/siw/siw_verbs.c
>> +++ b/drivers/infiniband/sw/siw/siw_verbs.c
>> @@ -1049,7 +1049,7 @@ int siw_create_cq(struct ib_cq *base_cq,
>const struct ib_cq_init_attr *attr,
>>
>> spin_lock_init(&cq->lock);
>>
>> - cq->notify = &((struct siw_cq_ctrl *)&cq->queue[size])->notify;
>> + cq->notify = (struct siw_cq_ctrl *)&cq->queue[size];
>>
>> if (udata) {
>> struct siw_uresp_create_cq uresp = {};
>> @@ -1141,11 +1141,17 @@ int siw_req_notify_cq(struct ib_cq
>*base_cq, enum ib_cq_notify_flags flags)
>> siw_dbg_cq(cq, "flags: 0x%02x\n", flags);
>>
>> if ((flags & IB_CQ_SOLICITED_MASK) == IB_CQ_SOLICITED)
>> - /* CQ event for next solicited completion */
>> - smp_store_mb(*cq->notify, SIW_NOTIFY_SOLICITED);
>> + /*
>> + * Enable CQ event for next solicited completion.
>> + * and make it visible to all associated producers.
>> + */
>> + smp_store_mb(cq->notify->flags, SIW_NOTIFY_SOLICITED);
>> else
>> - /* CQ event for any signalled completion */
>> - smp_store_mb(*cq->notify, SIW_NOTIFY_ALL);
>> + /*
>> + * Enable CQ event for any signalled completion.
>> + * and make it visible to all associated producers.
>> + */
>> + smp_store_mb(cq->notify->flags, SIW_NOTIFY_ALL);
>
>this isn't what we talked about, is it?
I actually abandoned the test_and_clear_bit() thing, since it
requires an unsigned long as the bitfield. This would make the
abi-file arch dependent with the hassle of #ifdef 64 or 32 bit
stuff in there.
>
>> index 7de68f1dc707..af735f55b291 100644
>> --- a/include/uapi/rdma/siw-abi.h
>> +++ b/include/uapi/rdma/siw-abi.h
>> @@ -180,6 +180,7 @@ struct siw_cqe {
>> * to control CQ arming.
>> */
>> struct siw_cq_ctrl {
>> - __aligned_u64 notify;
>> + __u32 flags;
>> + __u32 pad;
>
>The commit message needs to explain why this is compatible with
>existing user space, if it is even is safe..
>
Old libsiw would remain compatible with the new layout, since it
simply reads the 32bit 'flags' and zeroed 32bit 'pad' into a 64bit
'notify', ending with reading the same bits.
Thanks
Bernard.
