On Tue, 2024-01-02 at 10:35 +0800, Huacai Chen wrote: /* snip */ > > The only other architecture setting FCSR in SET_PERSONALITY2 is MIPS. > > They do this for supporting different FP flavors (NaN encodings etc). > > which do not exist on LoongArch. I'm not sure how MIPS evades the issue > > (or maybe it's just buggy too) as I don't have a running MIPS hardware > > now. > I think you can use QEMU. :) I'll investigate it later. > > So for LoongArch, just remove the current->thread.fpu.fcsr setting from > > SET_PERSONALITY2 and do it in start_thread, after lose_fpu(0). And we > > just set it to 0, instead of boot_cpu_data.fpu_csr0 (because we should > > provide the userspace a consistent configuration, no matter how hardware > > and firmware behave). > I still prefer to set fcsr to boot_cpu_data.fpu_csr0, because we will > add LoongArch32 later, not sure whether something will change. I just seen fpu_csr0 is initialized to FPU_CSR_RN which is just 0 for LA64, so my concern about firmware & hardware leaving non-zero FCSR is not valid. I'll send v2 to keep using boot_cpu_data.fpu_csr0 then. > > -- Xi Ruoyao <xry111@xxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
