linux-kernel - Re: [PATCH rdma-next 02/10] RDMA/core: Enable Relaxed Ordering in __ib_alloc

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Message-ID: <befc60f3-d28a-5420-b381-0f408bd7cca9@talpey.com>
Date:   Mon, 5 Apr 2021 14:01:16 -0400
From:   Tom Talpey <tom@...pey.com>
To:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>
Cc:     Avihai Horon <avihaih@...dia.com>,
        Adit Ranadive <aditr@...are.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Ariel Elior <aelior@...vell.com>,
        Bart Van Assche <bvanassche@....org>,
        Bernard Metzler <bmt@...ich.ibm.com>,
        Christoph Hellwig <hch@....de>,
        Chuck Lever <chuck.lever@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Devesh Sharma <devesh.sharma@...adcom.com>,
        Faisal Latif <faisal.latif@...el.com>,
        Jack Wang <jinpu.wang@...os.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Jens Axboe <axboe@...com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        Keith Busch <kbusch@...nel.org>, Lijun Ou <oulijun@...wei.com>,
        linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-rdma@...r.kernel.org, linux-s390@...r.kernel.org,
        Max Gurtovoy <maxg@...lanox.com>,
        Max Gurtovoy <mgurtovoy@...dia.com>,
        "Md. Haris Iqbal" <haris.iqbal@...os.com>,
        Michael Guralnik <michaelgur@...dia.com>,
        Michal Kalderon <mkalderon@...vell.com>,
        Mike Marciniszyn <mike.marciniszyn@...nelisnetworks.com>,
        Naresh Kumar PBS <nareshkumar.pbs@...adcom.com>,
        netdev@...r.kernel.org, Potnuri Bharat Teja <bharat@...lsio.com>,
        rds-devel@....oracle.com, Sagi Grimberg <sagi@...mberg.me>,
        samba-technical@...ts.samba.org,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        Selvin Xavier <selvin.xavier@...adcom.com>,
        Shiraz Saleem <shiraz.saleem@...el.com>,
        Somnath Kotur <somnath.kotur@...adcom.com>,
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        Steve French <sfrench@...ba.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        VMware PV-Drivers <pv-drivers@...are.com>,
        Weihang Li <liweihang@...wei.com>,
        Yishai Hadas <yishaih@...dia.com>,
        Zhu Yanjun <zyjzyj2000@...il.com>
Subject: Re: [PATCH rdma-next 02/10] RDMA/core: Enable Relaxed Ordering in
 __ib_alloc_pd()

On 4/5/2021 1:23 AM, Leon Romanovsky wrote:
> From: Avihai Horon <avihaih@...dia.com>
> 
> Enable Relaxed Ordering in __ib_alloc_pd() allocation of the
> local_dma_lkey.
> 
> This will take effect only for devices that don't pre-allocate the lkey
> but allocate it per PD allocation.
> 
> Signed-off-by: Avihai Horon <avihaih@...dia.com>
> Reviewed-by: Michael Guralnik <michaelgur@...dia.com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>   drivers/infiniband/core/verbs.c              | 3 ++-
>   drivers/infiniband/hw/vmw_pvrdma/pvrdma_mr.c | 1 +
>   2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
> index a1782f8a6ca0..9b719f7d6fd5 100644
> --- a/drivers/infiniband/core/verbs.c
> +++ b/drivers/infiniband/core/verbs.c
> @@ -287,7 +287,8 @@ struct ib_pd *__ib_alloc_pd(struct ib_device *device, unsigned int flags,
>   	if (device->attrs.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY)
>   		pd->local_dma_lkey = device->local_dma_lkey;
>   	else
> -		mr_access_flags |= IB_ACCESS_LOCAL_WRITE;
> +		mr_access_flags |=
> +			IB_ACCESS_LOCAL_WRITE | IB_ACCESS_RELAXED_ORDERING;

So, do local_dma_lkey's get relaxed ordering unconditionally?

>   	if (flags & IB_PD_UNSAFE_GLOBAL_RKEY) {
>   		pr_warn("%s: enabling unsafe global rkey\n", caller);
> diff --git a/drivers/infiniband/hw/vmw_pvrdma/pvrdma_mr.c b/drivers/infiniband/hw/vmw_pvrdma/pvrdma_mr.c
> index b3fa783698a0..d74827694f92 100644
> --- a/drivers/infiniband/hw/vmw_pvrdma/pvrdma_mr.c
> +++ b/drivers/infiniband/hw/vmw_pvrdma/pvrdma_mr.c
> @@ -66,6 +66,7 @@ struct ib_mr *pvrdma_get_dma_mr(struct ib_pd *pd, int acc)
>   	int ret;
>   
>   	/* Support only LOCAL_WRITE flag for DMA MRs */
> +	acc &= ~IB_ACCESS_RELAXED_ORDERING;
>   	if (acc & ~IB_ACCESS_LOCAL_WRITE) {
>   		dev_warn(&dev->pdev->dev,
>   			 "unsupported dma mr access flags %#x\n", acc);

Why does the pvrdma driver require relaxed ordering to be off?

Tom.