On Thu, May 25, 2017 at 04:07:08PM +0200, Paolo Bonzini wrote: > I think we should do the fixup backwards. > > That is: > > - first do get_fpu > > - if the fixup is necessary, i.e. ctxt->mode < X86EMUL_MODE_PROT64, do > fxsave into &fxstate. > > - then do segmented_read_std with the correct size, which is > - offsetof(struct fxregs_state, xmm_space[16]), i.e. 416 > if ctxt->mode == X86EMUL_MODE_PROT64 > - offsetof(struct fxregs_state, xmm_space[8]), i.e. 288 > if ctxt->mode < X86EMUL_MODE_PROT64 and CR4.OSFXSR=1 > - offsetof(struct fxregs_state, xmm_space[0]), i.e. 160 > if ctxt->mode < X86EMUL_MODE_PROT64 and CR4.OSFXSR=0 but we still want to do a segmented_read_std with size 512 otherwise, correct? > - then check fx_state.mxcsr > > - then do fxrstor This sounds like we conditionally do the fxsave, but then always do the fxrstor. Is that ok? I guess the original code kind of does that as well. > - finally do put_fpu Sounds straight forward. I can see how fxsave and CR4.OSFXSR are accessed in fxstor_fixup. Is it ok to skip those memcpy's that would otherwise occur when calling fxrstor_fixup() (which after these changes, we would not be)?
