Just curious, do MIPS CPUs actually do speculative execution?

(In reply to Jan de Mooij [:jandem] from comment #1) > Just curious, do MIPS CPUs actually do speculative execution? There are designs that do in the wild. Unfortunately I don't have enough data at this point which ones that do are vulnerable if any (except these [0]). This issue is more to evaluate of performance impact of Spectre mitigation primitives if they are enabled by default. [0] https://www.mips.com/blog/mips-response-on-speculative-execution-and-side-channel-vulnerabilities/

Patch contains current primitives w/o MacroAssembler::spectreMovePtr which can't be implemented on MIPS with its current API surface. If we want or need all of these mitigations usages of this method have to be refactored to not relay on presence of comparation flags. For now I'm interested on overhead of these mitigations on Loongson in Octane benchmark suite.

just have a quick test after apply this patch: [loongson@localhost octane]$ ../build_release/dist/bin/js run.js Richards: 4257 DeltaBlue: 10638 Crypto: 4787 RayTrace: 14711 EarleyBoyer: 6092 RegExp: 702 Splay: 1815 SplayLatency: 1147 NavierStokes: 7990 PdfJS: 2626 Mandreel: 2950 MandreelLatency: 3382 Gameboy: 7529 CodeLoad: 4926 Box2D: 6407 zlib: 11125 Typescript: 6223 ---- Score (version 9): 4431 [loongson@localhost octane]$ ../build_release/dist/bin/js run.js Richards: 4264 DeltaBlue: 10685 Crypto: 4776 RayTrace: 15066 EarleyBoyer: 6048 RegExp: 734 Splay: 4184 SplayLatency: 1244 NavierStokes: 7950 PdfJS: 2670 Mandreel: 2948 MandreelLatency: 3382 Gameboy: 8643 CodeLoad: 4917 Box2D: 6423 zlib: 11148 Typescript: 6041 ---- Score (version 9): 4728 -------------------------------- [loongson@localhost octane]$ ../build_release/dist/bin/js --spectre-mitigations=off run.js Richards: 4293 DeltaBlue: 11220 Crypto: 4898 RayTrace: 15773 EarleyBoyer: 6242 RegExp: 739 Splay: 3423 SplayLatency: 1906 NavierStokes: 8383 PdfJS: 2738 Mandreel: 3074 MandreelLatency: 3353 Gameboy: 11485 CodeLoad: 4940 Box2D: 6336 zlib: 11646 Typescript: 6105 ---- Score (version 9): 4965 [loongson@localhost octane]$ ../build_release/dist/bin/js --spectre-mitigations=off run.js Richards: 4282 DeltaBlue: 10995 Crypto: 4890 RayTrace: 15540 EarleyBoyer: 6221 RegExp: 749 Splay: 3520 SplayLatency: 1913 NavierStokes: 8472 PdfJS: 2763 Mandreel: 3055 MandreelLatency: 3371 Gameboy: 10818 CodeLoad: 4920 Box2D: 6360 zlib: 11651 Typescript: 6052 ---- Score (version 9): 4951

(In reply to yuyin from comment #4) > just have a quick test after apply this patch: Sorry for the late replay. Those numbers look nice. I tend to get a slightly worse numbers in ballpark of ~5% - 10%. I'll try to finish this in couple of weeks. There are still some missing peaces like unboxing on mips32 and spectreMovePtr then I'll do more testing. Not sure for now, the plan will be to leave this mitigations in but disabled by default at least on mips32.

hi. you can see with --spectre-mitigations on, lead to performance decline on loongson too, and looks like current loongson cpus are not affected by this vulnerability. so can you also disable it by default on mips64 like mips32. thank you. (In reply to Dragan Mladjenovic from comment #5) > (In reply to yuyin from comment #4) > > just have a quick test after apply this patch: > > Sorry for the late replay. > > Those numbers look nice. I tend to get a slightly worse numbers in ballpark > of ~5% - 10%. > I'll try to finish this in couple of weeks. There are still some missing > peaces > like unboxing on mips32 and spectreMovePtr then I'll do more testing. Not > sure for now, > the plan will be to leave this mitigations in but disabled by default at > least on mips32.