Re: [dpdk-dev] [PATCH v1 0/3] relax io barrier for aarch64 and use smp barriers for virtual pci memory

["Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Wednesday, October 23, 2019 4:23 PM
> To: Gavin Hu (Arm Technology China) <Gavin.Hu@arm.com>; dev@dpdk.org
> Cc: nd <nd@arm.com>; david.marchand@redhat.com; tiwei.bie@intel.com;
> thomas@monjalon.net; rasland@mellanox.com; matan@mellanox.com;
> shahafs@mellanox.com; viacheslavo@mellanox.com;
> arybchenko@solarflare.com; stephen@networkplumber.org;
> hemant.agrawal@nxp.com; jerinj@marvell.com;
> pbhagavatula@marvell.com; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang (Arm Technology China)
> <Ruifeng.Wang@arm.com>; Phil Yang (Arm Technology China)
> <Phil.Yang@arm.com>; Joyce Kong (Arm Technology China)
> <Joyce.Kong@arm.com>; Steve Capper <Steve.Capper@arm.com>
> Subject: Re: [PATCH v1 0/3] relax io barrier for aarch64 and use smp barriers
> for virtual pci memory
> 
> Hi Gavin,
> 
> On 10/22/19 5:27 PM, Gavin Hu wrote:
> > Armv8's peripheral coherence order is a total order on all reads and
> > writes to that peripheral, that makes a compiler barrier is enough for
> > abstracted rte io barrier.
> >
> > For virtual PCI devices, the virtual device memory is actually normal
> > memory and the Hypervisor view of things takes precedence and they are
> > within a smp configuration and smp barriers should be used, the
> > relaxed io barrier for aarch64 becomes insufficient.
> 
> IIUC, this series is for performance optimization and not fixing
> coherency issues. Can you confirm?
Yes, this is for perf optimization.
> 
> If that's the case, I'm afraid we'll have to postpone it to v20.02,
> our patch queues are already too big at that stage of the release.
Ok, no problem, thanks!
> 
> Maxime
> 
> > Gavin Hu (3):
> >   eal/arm64: relax the io barrier for aarch64
> >   net/virtio: virtual PCI requires smp barriers
> >   crypto/virtio: virtual PCI requires smp barriers
> >
> >  drivers/crypto/virtio/virtio_pci.c                 | 124 ++++++++++++++++-----
> >  drivers/net/virtio/virtio_pci.c                    | 124 ++++++++++++++++-----
> >  .../common/include/arch/arm/rte_atomic_64.h        |   6 +-
> >  3 files changed, 191 insertions(+), 63 deletions(-)
> >