linux-kernel - Re: [PATCH v2 rdma-next] RDMA/mlx5: Enable Relaxed Ordering by default for kernel ULPs

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Date:   Sun, 27 Jun 2021 10:32:23 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Max Gurtovoy <mgurtovoy@...dia.com>,
        Doug Ledford <dledford@...hat.com>,
        Avihai Horon <avihaih@...dia.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Bart Van Assche <bvanassche@....org>,
        Tom Talpey <tom@...pey.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        Chuck Lever III <chuck.lever@...cle.com>,
        Keith Busch <kbusch@...nel.org>,
        David Laight <David.Laight@...lab.com>,
        Honggang LI <honli@...hat.com>
Subject: Re: [PATCH v2 rdma-next] RDMA/mlx5: Enable Relaxed Ordering by
 default for kernel ULPs

On Thu, Jun 24, 2021 at 08:36:07AM -0300, Jason Gunthorpe wrote:
> On Thu, Jun 24, 2021 at 10:39:16AM +0300, Max Gurtovoy wrote:
> > 
> > On 6/24/2021 9:38 AM, Leon Romanovsky wrote:
> > > On Thu, Jun 24, 2021 at 02:06:46AM +0300, Max Gurtovoy wrote:
> > > > On 6/9/2021 2:05 PM, Leon Romanovsky wrote:
> > > > > From: Avihai Horon <avihaih@...dia.com>
> > > > > 
> > > > > Relaxed Ordering is a capability that can only benefit users that support
> > > > > it. All kernel ULPs should support Relaxed Ordering, as they are designed
> > > > > to read data only after observing the CQE and use the DMA API correctly.
> > > > > 
> > > > > Hence, implicitly enable Relaxed Ordering by default for kernel ULPs.
> > > > > 
> > > > > Signed-off-by: Avihai Horon <avihaih@...dia.com>
> > > > > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > > > > Changelog:
> > > > > v2:
> > > > >    * Dropped IB/core patch and set RO implicitly in mlx5 exactly like in
> > > > >      eth side of mlx5 driver.
> > > > > v1: https://lore.kernel.org/lkml/cover.1621505111.git.leonro@nvidia.com
> > > > >    * Enabled by default RO in IB/core instead of changing all users
> > > > > v0: https://lore.kernel.org/lkml/20210405052404.213889-1-leon@kernel.org
> > > > >    drivers/infiniband/hw/mlx5/mr.c | 10 ++++++----
> > > > >    drivers/infiniband/hw/mlx5/wr.c |  5 ++++-
> > > > >    2 files changed, 10 insertions(+), 5 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
> > > > > index 3363cde85b14..2182e76ae734 100644
> > > > > +++ b/drivers/infiniband/hw/mlx5/mr.c
> > > > > @@ -69,6 +69,7 @@ static void set_mkc_access_pd_addr_fields(void *mkc, int acc, u64 start_addr,
> > > > >    					  struct ib_pd *pd)
> > > > >    {
> > > > >    	struct mlx5_ib_dev *dev = to_mdev(pd->device);
> > > > > +	bool ro_pci_enabled = pcie_relaxed_ordering_enabled(dev->mdev->pdev);
> > > > >    	MLX5_SET(mkc, mkc, a, !!(acc & IB_ACCESS_REMOTE_ATOMIC));
> > > > >    	MLX5_SET(mkc, mkc, rw, !!(acc & IB_ACCESS_REMOTE_WRITE));
> > > > > @@ -78,10 +79,10 @@ static void set_mkc_access_pd_addr_fields(void *mkc, int acc, u64 start_addr,
> > > > >    	if (MLX5_CAP_GEN(dev->mdev, relaxed_ordering_write))
> > > > >    		MLX5_SET(mkc, mkc, relaxed_ordering_write,
> > > > > -			 !!(acc & IB_ACCESS_RELAXED_ORDERING));
> > > > > +			 acc & IB_ACCESS_RELAXED_ORDERING && ro_pci_enabled);
> > > > >    	if (MLX5_CAP_GEN(dev->mdev, relaxed_ordering_read))
> > > > >    		MLX5_SET(mkc, mkc, relaxed_ordering_read,
> > > > > -			 !!(acc & IB_ACCESS_RELAXED_ORDERING));
> > > > > +			 acc & IB_ACCESS_RELAXED_ORDERING && ro_pci_enabled);
> > > > Jason,
> > > > 
> > > > If it's still possible to add small change, it will be nice to avoid
> > > > calculating "acc & IB_ACCESS_RELAXED_ORDERING && ro_pci_enabled" twice.
> > > The patch is part of for-next now, so feel free to send followup patch.
> > > 
> > > Thanks
> > > 
> > > diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
> > > index c1e70c99b70c..c4f246c90c4d 100644
> > > +++ b/drivers/infiniband/hw/mlx5/mr.c
> > > @@ -69,7 +69,8 @@ static void set_mkc_access_pd_addr_fields(void *mkc, int acc, u64 start_addr,
> > >                                            struct ib_pd *pd)
> > >   {
> > >          struct mlx5_ib_dev *dev = to_mdev(pd->device);
> > > -       bool ro_pci_enabled = pcie_relaxed_ordering_enabled(dev->mdev->pdev);
> > > +       bool ro_pci_enabled = acc & IB_ACCESS_RELAXED_ORDERING &&
> > > +                             pcie_relaxed_ordering_enabled(dev->mdev->pdev);
> > > 
> > >          MLX5_SET(mkc, mkc, a, !!(acc & IB_ACCESS_REMOTE_ATOMIC));
> > >          MLX5_SET(mkc, mkc, rw, !!(acc & IB_ACCESS_REMOTE_WRITE));
> > > @@ -78,11 +79,9 @@ static void set_mkc_access_pd_addr_fields(void *mkc, int acc, u64 start_addr,
> > >          MLX5_SET(mkc, mkc, lr, 1);
> > > 
> > >          if (MLX5_CAP_GEN(dev->mdev, relaxed_ordering_write))
> > > -               MLX5_SET(mkc, mkc, relaxed_ordering_write,
> > > -                        (acc & IB_ACCESS_RELAXED_ORDERING) && ro_pci_enabled);
> > > +               MLX5_SET(mkc, mkc, relaxed_ordering_write, ro_pci_enabled);
> > >          if (MLX5_CAP_GEN(dev->mdev, relaxed_ordering_read))
> > > -               MLX5_SET(mkc, mkc, relaxed_ordering_read,
> > > -                        (acc & IB_ACCESS_RELAXED_ORDERING) && ro_pci_enabled);
> > > +               MLX5_SET(mkc, mkc, relaxed_ordering_read, ro_pci_enabled);
> > > 
> > >          MLX5_SET(mkc, mkc, pd, to_mpd(pd)->pdn);
> > >          MLX5_SET(mkc, mkc, qpn, 0xffffff);
> > > (END)
> > > 
> > Yes this looks good.
> > 
> > Can you/Avihai create a patch from this ? or I'll do it ?
> 
> I'd be surpised if it matters.. CSE and all

>From bytecode/performance POV, It shouldn't change anything.
However it looks better.

Thanks

> 
> Jason