On Tue, Feb 26, 2013 at 05:37:17PM -0800, Stephen Boyd wrote: > On 02/25/13 12:02, Russell King - ARM Linux wrote: > > > > This can of worms is getting bigger. We have more problems with our > > handling of the different VFP versions, specifically the handling of > > the EX=0 DEX=0 case. > > > > VFP common subarch 3 defines the EX=0, DEX=0 encoding to mean one of > > the following conditions have been met: > > > > 1. an unallocated VFP instruction was encountered. > > > > In other words, the VFP was the target of the co-processor instruction, > > but the instruction is not a known VFP instruction encoding. This > > should raise an undefined instruction exception. > > > > 2. an allocated VFP instruction was encountered, but not handled in > > hardware. > > > > In other words, the instruction is a valid VFP instruction, but the > > hardware has opted not to implement this instruction and wants > > software to emulate it instead. > > > > (Note: this can also be raised as EX=0, DEX=1 - implementation > > defined!) > > > [snip] > > > > So, if EX or DEX is set, _or_ IXE is set, we pass control to VFP_bounce. > > This is problematical. > > > > (a) condition (2) above isn't correctly handled for common subarch v3 - it > > is always treated as an undefined instruction, and will result in a > > SIGILL being delivered. > > > [snip] > > > > Now, (a) is just bad behaviour - as we haven't had any reports of this > > yet, I suspect that no one has implemented VFP hardware with this > > behaviour yet. > > I believe we ran into this a while ago and fixed it for our chips. We > never sent the patch upstream. Sorry. > > https://www.codeaurora.org/gitweb/quic/la/?p=kernel/msm.git;a=commitdiff;h=00a13be874f230159a6b7f8cc9d0ff23bc1b7d05 Yes, it looks like you did - because your short vector instructions are "allocated VFP instruction"s and your hardware response is to raise an exception with EX=0 DEX=0. As you've found out, with the VFPv2 exception handling that we have, that is interpreted as an undefined instruction, rather than an instruction which needs fixing up. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
