On 03/24/2015 08:18 PM, Andy Lutomirski wrote: > On Tue, Mar 24, 2015 at 5:12 PM, Dave Hansen <dave.han...@intel.com> wrote:
>> I won't completely claim to understand what's going on with the FPU >> code, but I think your analysis is a bit off. >> >> unlazy_fpu() does __save_init_fpu() which (among other things) calls >> xsave to dump the CPU registers to memory. That doesn't make any sense >> to do if "The in-memory copy and the CPU regs match." >> >> IOW, unlazy_fpu() is called when the in-memory copy is garbage and takes >> us to a state where we can look at the in-memory copy. > > I think that __save_init_fpu (called by unlazy_fpu) does that, but > __thread_fpu_end calls __thread_clear_has_fpu, which, in turn, zaps > fpu_owner_task, which will force an unnecessary xrstor. Or maybe not > if we have further bugs. Indeed, __save_init_fpu (yeah, terrible name) will save the in-register state to memory for you, so you can inspect it. Is there any reason not to rename __save_init_fpu to save_fpu_state, or just save_fpu? -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
