Date: Mon, 25 Jan 2021 16:21:40 -0500 From: Allan Jude <allanjude@freebsd.org> To: Andrew Gallatin <gallatin@cs.duke.edu>, John Baldwin <jhb@FreeBSD.org>, freebsd-arch@FreeBSD.org, Ed Maste <emaste@FreeBSD.org> Subject: Re: Should we enable KERN_TLS on amd64 for FreeBSD 13? Message-ID: <545e9227-a4a2-8c77-1400-c4371b654f36@freebsd.org> In-Reply-To: <7c8f5dfa-3ae5-5620-2505-2324d41deaca@cs.duke.edu> References: <8eff83e5-49bc-d410-626e-603c03877b80@cs.duke.edu> <d3505804-e55f-dfad-7027-060d05675d4a@freebsd.org> <ecc65818-9426-e366-11b4-300e8608f99e@FreeBSD.org> <7c8f5dfa-3ae5-5620-2505-2324d41deaca@cs.duke.edu>
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On 2021-01-25 15:33, Andrew Gallatin wrote: > On 1/25/21 2:59 PM, John Baldwin wrote: >> On 1/25/21 10:45 AM, Allan Jude wrote: >>> On 2021-01-08 12:26, Andrew Gallatin wrote: >>>> >>>> Kernel TLS (KTLS) support was added roughly a year ago, and provides >>>> an efficient software or hardware accelerated path to have the kernel >>>> (or the NIC) handle TLS crypto. This is quite useful for web and >>>> NFS servers, and provides a huge (2x -> 5x) efficiency gain by >>>> avoiding data copies into userspace for crypto, and potentially >>>> offloading the crypto to hardware. >>>> >>>> >>>> KTLS is well tested on amd64, having been used in production at Netflix >>>> for nearly 4 years. The vast majority of Netflix video has been >>>> served >>>> via KTLS for the last few years. Its what has allowed us to serve >>>> 100Gb/s on Xeon 2697A cpus for years, and what allows us to serve >>>> nearly 400Gb/s on AMD servers with NICs which support crypto offload. >>>> >>>> I have received a few requests to enable it by default in GENERIC, and >>>> I'd like to get some opinions. >>>> >>>> There are essentially 3 options >>>> >>>> 1) Fully enable KTLS by adding 'options KERN_TLS' to GENERIC, and >>>> flipping kern.ipc.tls.enable=1 >>>> >>>> The advantage of this is that it "just works" out of the box for users, >>>> and for reviewers. >>>> >>>> The drawback is that new code is thrust on unsuspecting users, >>>> potentially exposing them to bugs that we have not found in our >>>> somewhat limited web serving workload. >>>> >>>> 2) Enable KTLS in GENERIC, but leave it turned off by default. >>>> >>>> This option allows users to enable ktls without a rebuild of GENERIC, >>>> but does not enable it by default. So they can enable it if they >>>> know about it, but are protected from bugs. >>>> >>>> The disadvantages of this are that it increases the kernel size >>>> by ~20K, starts up one thread per core on every amd64 machine, >>>> and it adds more required tuning to get good performance from FreeBSD. >>>> >>>> >>>> 3) Continue along with KTLS disabled in GENERIC >>>> >>>> This is the lowest risk, but adds a higher bar for users wanting >>>> to use ktls. >>>> >>>> >>>> >>>> Note that the discussion is focused on amd64 only, as KTLS will >>>> only work on 64-bit platforms which use a direct map. It has >>>> not been tested at all on ppc64, and currently causes a >>>> panic-at-boot on arm64 due to what are suspected to be problems >>>> in the arm64 PCB setup. See: >>>> https://urldefense.com/v3/__https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247945__;!!OToaGQ!7pQUcHPbxA12vEdKTCp5jkyVxDCqYEJ-BI38kgHqGgweT7yYYG1BVhbDek0_Jc7mqA$ >>>> >>>> Drew >>>> >>> >>> Just before this went in, Ed cleaned up the arm64 GENERIC to get it >>> closer to the amd64 one. Can we enable KERN_TLS in arm64 GENERIC as >>> well? >> >> Well, I also fixed a bug KERN_TLS exposed on arm64 that was gating for >> this (247945). I would not be opposed to enabling it on arm64, but I >> have not personally tested it on arm64. If someone can verify it works >> ok on arm64 I'd be happy for it to be enabled there. >> > > Yeah, that's the thing, I have much less confidence in ktls on arm64 > because we have not run it in production recently. So I'm personally > much less confident in enabling it on arm64. > > Drew Klara has tested it on arm64 fairly heavily, and only found an issue with OpenSSL, but not found any issues with KERN_TLS itself. -- Allan Jude
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