From: Jason Gunthorpe <jgg@nvidia.com>
To: "Rimmer, Todd" <todd.rimmer@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
"Wan, Kaike" <kaike.wan@intel.com>,
"dledford@redhat.com" <dledford@redhat.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH RFC 0/9] A rendezvous module
Date: Tue, 23 Mar 2021 14:44:23 -0300 [thread overview]
Message-ID: <20210323174423.GK2356281@nvidia.com> (raw)
In-Reply-To: <BL0PR11MB3299B764F783B77F018CC759F6649@BL0PR11MB3299.namprd11.prod.outlook.com>
On Tue, Mar 23, 2021 at 05:25:43PM +0000, Rimmer, Todd wrote:
> In studying all the related fields, in most cases if we shuffled
> everything for maximum packing, the structures would still end up
> being about the same size and this would all be for non-performance
> path ABIs.
It is not about size, it is about uABI compatability. Do not place
packing holes in uABI structures as it is *very complicated* to
guarentee those work across all the combinations of user/kernel we
have to support.
Every uABI structure should have explicit padding, it should be
organized to minimize padding, and "easy on the programmer" is not a
top concern.
You must ensure that all compilers generate the same structure byte
layout. On x86 this means a classic i386 compiler, a AMD64 x32 ABI,
and the normal AMD64 compiler.
> It should be noted, there are existing examples with small gaps or
> reserved fields in the existing kernel and RDMA stack. A few
> examples in ib_user_verbs.h include:
Past mistakes do not excuse future errors. Most of those are not uABI
structs.
Jason
next prev parent reply other threads:[~2021-03-23 17:45 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 12:56 [PATCH RFC 0/9] A rendezvous module kaike.wan
2021-03-19 12:56 ` [PATCH RFC 1/9] RDMA/rv: Public interferce for the RDMA Rendezvous module kaike.wan
2021-03-19 16:00 ` Jason Gunthorpe
2021-03-19 18:42 ` kernel test robot
2021-03-19 12:56 ` [PATCH RFC 2/9] RDMA/rv: Add the internal header files kaike.wan
2021-03-19 16:02 ` Jason Gunthorpe
2021-03-19 12:56 ` [PATCH RFC 3/9] RDMA/rv: Add the rv module kaike.wan
2021-03-19 12:56 ` [PATCH RFC 4/9] RDMA/rv: Add functions for memory region cache kaike.wan
2021-03-19 12:56 ` [PATCH RFC 5/9] RDMA/rv: Add function to register/deregister memory region kaike.wan
2021-03-19 12:56 ` [PATCH RFC 6/9] RDMA/rv: Add connection management functions kaike.wan
2021-03-19 12:56 ` [PATCH RFC 7/9] RDMA/rv: Add functions for RDMA transactions kaike.wan
2021-03-19 12:56 ` [PATCH RFC 8/9] RDMA/rv: Add functions for file operations kaike.wan
2021-03-19 12:56 ` [PATCH RFC 9/9] RDMA/rv: Integrate the file operations into the rv module kaike.wan
2021-03-19 13:53 ` [PATCH RFC 0/9] A rendezvous module Jason Gunthorpe
2021-03-19 14:49 ` Wan, Kaike
2021-03-19 15:48 ` Jason Gunthorpe
2021-03-19 19:22 ` Dennis Dalessandro
2021-03-19 19:44 ` Jason Gunthorpe
2021-03-19 20:12 ` Rimmer, Todd
2021-03-19 20:26 ` Jason Gunthorpe
2021-03-19 20:46 ` Rimmer, Todd
2021-03-19 20:54 ` Jason Gunthorpe
2021-03-19 20:59 ` Wan, Kaike
2021-03-19 21:28 ` Dennis Dalessandro
2021-03-19 21:58 ` Wan, Kaike
2021-03-19 22:35 ` Jason Gunthorpe
2021-03-19 22:57 ` Rimmer, Todd
2021-03-19 23:06 ` Jason Gunthorpe
2021-03-20 16:39 ` Dennis Dalessandro
2021-03-21 8:56 ` Leon Romanovsky
2021-03-21 16:24 ` Dennis Dalessandro
2021-03-21 16:45 ` Jason Gunthorpe
2021-03-21 17:21 ` Dennis Dalessandro
2021-03-21 18:08 ` Jason Gunthorpe
2021-03-22 15:17 ` Rimmer, Todd
2021-03-22 16:47 ` Jason Gunthorpe
2021-03-22 17:31 ` Hefty, Sean
2021-03-23 22:56 ` Jason Gunthorpe
2021-03-23 23:29 ` Rimmer, Todd
2021-03-21 19:19 ` Wan, Kaike
2021-03-23 15:36 ` Christoph Hellwig
2021-03-23 15:35 ` Christoph Hellwig
2021-03-23 15:33 ` Christoph Hellwig
2021-03-23 15:30 ` Christoph Hellwig
2021-03-23 15:46 ` Jason Gunthorpe
2021-03-23 16:07 ` Christoph Hellwig
2021-03-23 17:25 ` Rimmer, Todd
2021-03-23 17:44 ` Jason Gunthorpe [this message]
2021-03-19 20:18 ` Dennis Dalessandro
2021-03-19 20:30 ` Jason Gunthorpe
2021-03-19 20:34 ` Hefty, Sean
2021-03-21 12:08 ` Jason Gunthorpe
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