Quoting Filip Pizlo (2018-02-19 13:05:27) > > > On Feb 19, 2018, at 10:53 AM, Guillaume Emont <guijem...@igalia.com> wrote: > > > > Hi Keith, > > > > We at Igalia have been trying to provide a better story for 32-bit > > platforms, in particular for Armv7 and MIPS. These platforms are very > > important to us, and disabling JIT renders many use cases impossible. > > What use cases?
I'm not sure of how much I can elaborate here, but in this particular case that was for a set-top-box UI. > > I realize that having a JIT is good for marketing, but it’s better to have a > stable and well-maintained interpreter than a decrepit JIT. Right now the > 32-bit JIT is basically unmaintained. Indeed these platforms used to be practically abandoned in WebKit. I don't think that is true any more though. We've been working on fixing this and getting mips32 and armv7+thumb2 to pass all the tests. We have achieved that for mips32[1] and we are almost there for armv7[2]. I would appreciate it if you could acknowledge that effort. [1] https://build.webkit.org/builders/JSCOnly%20Linux%20MIPS32el%20Release [2] https://build.webkit.org/builders/JSCOnly%20Linux%20ARMv7%20Thumb2%20Release > > > We > > want to continue this effort to support these platforms. We have been > > short on resources for that effort, which is why we did not realize > > early enough that more mitigation was needed for 32-bit platforms. We > > now have grown our team dedicated to this and we are hopeful that we > > will avoid that kind of issue in the future. > > I feel like I’ve heard this exact story before. Every time we say that there > isn’t any effort going into 32-bit, y’all say that you’ll put more effort > into it Real Soon Now. And then nothing happens, and we have the same > conversation in 6 months. I'm sorry it took us time to grow our team for this purpose, but that is now a reality since the beginning of this month. And beside that, I think you can agree that there has been significant progress on that aspect, we were very far from having a green tree on mips32 about a year ago, when we still had hundreds of test failures. > > > > > We are working on a plan to mitigate Spectre on 32-bit platforms. We > > would welcome community feedback on that, as well as what kinds of > > mitigations would be considered sufficient. > > > > Regarding your patch, I think you should note that some specific 32-bit > > CPUs are immune to Spectre (at least the Raspberry Pi[1] and some > > MIPS[2] devices), I think the deactivation should be done at run-time > > for CPUs not on a white list. > > Keith’s main point is that the presence of 32-bit makes it harder to > implement mitigations for 64-bit. I don’t think it’s justifiable to hold > back development of 64-bit Spectre mitigations because of a hardly-used and > mostly-broken 32-bit JIT port that will be maintained by someone Real Soon > Now. I can't answer to that as I don't know enough what is hindering these mitigations exactly. Best regards, Guillaume _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
