On 01/23/2017 08:55 AM, Yu-cheng Yu wrote: > On Mon, Jan 23, 2017 at 07:36:20AM -0800, Dave Hansen wrote: >> The kernel xsave buffer should *ALWAYS* have the >> XCOMP_BV_COMPACTED_FORMAT bit set. It should have been set before the >> copyin and it should be set when it's finished. >> >> The best fix here would be not to paper over the issue in the copy >> function but find where it got clobbered, or where some initialization >> code failed to set it. > > Someone else reported different issues from the same bug and a different > patch was just tested OK this morning. I think that adding xfeatures bits > to xcomp_bv should have been done in fpstate_init().
Right. So where did it get cleared out? > Also, in copy_init_fpstate_to_fpregs(), we do: > > copy_kernel_to_xregs(&init_fpstate.xsave, -1). > > That (-1) could mean (0) because the parameters are declared as: > > copy_kernel_to_xregs(struct xregs_state *, u64) I'm not sure what you're saying. -1 just means "all 1's" when cast to an unsigned type. This shouldn't case any problems.
