On Mon, 2014-01-20 at 20:43 -0600, Wang Dongsheng-B40534 wrote: > > > -----Original Message----- > > From: Wood Scott-B07421 > > Sent: Tuesday, January 21, 2014 9:06 AM > > To: Wang Dongsheng-B40534 > > Cc: b...@kernel.crashing.org; Zhao Chenhui-B35336; an...@enomsg.org; > > linuxppc- > > d...@lists.ozlabs.org > > Subject: Re: [PATCH 2/3] powerpc/85xx: Provide two functions to > > save/restore the > > core registers > > > > On Mon, 2014-01-20 at 00:03 -0600, Wang Dongsheng-B40534 wrote: > > > > > > > + /* > > > > > > > + * Need to save float-point registers if MSR[FP] = 1. > > > > > > > + */ > > > > > > > + mfmsr r12 > > > > > > > + andi. r12, r12, MSR_FP > > > > > > > + beq 1f > > > > > > > + do_sr_fpr_regs(save) > > > > > > > > > > > > C code should have already ensured that MSR[FP] is not 1 (and thus > > > > > > the > > FP > > > > > > context has been saved). > > > > > > > > > > > > > > > > Yes, right. But I mean if the FP still use in core save flow, we need > > > > > to > > save > > > > it. > > > > > In this process, i don't care what other code do, we need to focus on > > > > > not > > > > losing > > > > > valuable data. > > > > > > > > It is not allowed to use FP at that point. > > > > > > > If MSR[FP] not active, that is FP not allowed to use. > > > But here is a normal judgment, if MSR[FP] is active, this means that the > > floating > > > point module is being used. I offer is a function of the interface, we > > > don't > > know > > > where is the function will be called. Just because we call this function > > > in > > the > > > context of uncertainty, we need this judgment to ensure that no data is > > > lost. > > > > The whole point of calling enable_kernel_fp() in C code before > > suspending is to ensure that the FP state gets saved. If FP is used > > after that point it is a bug. If you're worried about such bugs, then > > clear MSR[FP] after calling enable_kernel_fp(), rather than adding > > redundant state saving. > > > > enable_kernel_fp() calling in MEM suspend flow. > Hibernation is different with MEM suspend, and I'm not sure where will call > this > interface, so we need to ensure the integrity of the core saving. I don't > think > this code is *redundant*. I trust that the kernel can keep the FP related > operations, that's why a judgment is here. :)
For hibernation, save_processor_state() is called first, which does flush_fp_to_thread() which has a similar effect (though I wonder if it's being called on the correct task for non-SMP). -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
