I used a very old userspace, and embedded systems are much more likely to use uclibc than glibc. However, if they try to use SSE without checking they will break on a hell of a lot more hardware.
On August 17, 2015 5:19:10 PM PDT, Andy Lutomirski <[email protected]> wrote: >On Mon, Aug 17, 2015 at 5:06 PM, H. Peter Anvin <[email protected]> wrote: >> User space does not need to treat for FPU instructions, except for >performance reasons, because the kernel emulates the full x87 FPU. So >it is localized to the kernel. > >But user space needs to avoid SSE2 and such, I suspect. In general, >I'd be surprised if things work well if we emulate the FPU (and set >CR0.em? I haven't checked out Linux's FPU emulation works) if user >code sees fancy instruction sets exposed and possibly even OSXSAVE. > >None of this matters except for testing, since it's very unlikely that >any CPU exists that supports XSAVE, XMM, SSE2, etc but uses emulated >x87. But if we emulate such a beast, things could break, and I bet >that's what Ingo's seeing. (Also, lots of distros target "i686" these >days, and that might cause its own set of problems.) > >--Andy -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
