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From: Jason Gunthorpe <jgg@nvidia.com>
To: Yishai Hadas <yishaih@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	"maorg@nvidia.com" <maorg@nvidia.com>,
	"cohuck@redhat.com" <cohuck@redhat.com>,
	liulongfang <liulongfang@huawei.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Shameerali Kolothum Thodi  <shameerali.kolothum.thodi@huawei.com>
Subject: Re: [PATCH vfio 2/2] vfio: Split migration ops from main device ops
Date: Mon, 20 Jun 2022 00:49:09 -0300	[thread overview]
Message-ID: <20220620034909.GC5219@nvidia.com> (raw)
In-Reply-To: <4f14e015-e4f7-7632-3cd7-0e644ed05c99@nvidia.com>

On Sun, Jun 19, 2022 at 12:25:50PM +0300, Yishai Hadas wrote:

> Means, staying with a single device_ops but just inline a check whether
> migration is really supported inside the migration get/set state callbacks
> and let the core call it unconditionally.

I find it much cleaner to have op == NULL means unsupported.

As soon as you start linking supported/unsupported to other flags it
can get very complicated fairly fast. I have this experiance from RDMA
where we've spent a long time now ripping out hundreds of flag tests
and replacing them with NULL op checks. Many bugs were fixed doing
this as drivers never fully understood what the flags mean and ended
up with flags set that their driver doesn't properly implement.

The mistake we made in RDMA was not splitting the ops, instead the ops
were left mutable so the driver could load the right combination based
on HW ability.

Jason

  reply	other threads:[~2022-06-20  3:49 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-06  8:56 [PATCH vfio 0/2] Migration few enhancements Yishai Hadas
2022-06-06  8:56 ` [PATCH vfio 1/2] vfio/mlx5: Protect mlx5vf_disable_fds() upon close device Yishai Hadas
2022-06-10  3:25   ` Tian, Kevin
2022-06-06  8:56 ` [PATCH vfio 2/2] vfio: Split migration ops from main device ops Yishai Hadas
2022-06-10  3:32   ` Tian, Kevin
2022-06-13  7:13     ` Yishai Hadas
2022-06-16 14:18       ` Yishai Hadas
2022-06-16 23:01         ` Alex Williamson
2022-06-17  3:58           ` Tian, Kevin
2022-06-17  4:04           ` Tian, Kevin
2022-06-17  8:50           ` Shameerali Kolothum Thodi
2022-06-17 14:47             ` Alex Williamson
2022-06-19  9:25               ` Yishai Hadas
2022-06-20  3:49                 ` Jason Gunthorpe [this message]
2022-06-21 16:41                   ` Alex Williamson
2022-06-24 14:12                     ` Jason Gunthorpe
2022-06-24 14:41                       ` Alex Williamson
2022-06-24 14:53                         ` Jason Gunthorpe

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