On Wed, 8 Sept 2021 at 17:28, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> wrote: > > On Wed, Sep 08, 2021 at 10:08:47AM +0800, 陈飞扬 wrote: > > On Tue, 7 Sept 2021 at 21:49, Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote: > > > > > > > > > 在 2021/9/7 14:16, FreeFlyingSheep 写道: > > > > From: Feiyang Chen <chenfeiyang@xxxxxxxxxxx> > > > > > > > > Convert mips syscall to use the generic entry infrastructure from > > > > kernel/entry/*. > > > > > > > > There are a few special things on mips: > > > > > > > > - There is one type of syscall on mips32 (scall32-o32) and three types > > > > of syscalls on mips64 (scall64-o32, scall64-n32 and scall64-n64). Now > > > > convert to C code to handle different types of syscalls. > > > > > > > > - For some special syscalls (e.g. fork, clone, clone3 and sysmips), > > > > save_static_function() wrapper is used to save static registers. Now > > > > SAVE_STATIC is used in handle_sys before calling do_syscall(), so the > > > > save_static_function() wrapper can be removed. > > > > > > > > - For sigreturn/rt_sigreturn and sysmips, inline assembly is used to > > > > jump to syscall_exit directly for skipping setting the error flag and > > > > restoring all registers. Now use regs->regs[27] to mark whether to > > > > handle the error flag and always restore all registers in handle_sys, > > > > so these functions can return normally as other architecture. > > > > > > Hmm, that would give us overhead of register context on these syscalls. > > > > > > I guess it's worthy? > > > > > > > Hi, Jiaxun, > > > > Saving and restoring registers against different system calls can be > > difficult due to the use of generic entry. > > To avoid a lot of duplicate code, I think the overhead is worth it. > > could you please provide numbers for that ? This code still runs > on low end MIPS CPUs for which overhead might mean a different > ballpark than some highend Loongson CPUs. Hi, Thomas, Jiaxun, Yanjie, Nikolaus, Thank you for your help. The impact on performance seems somewhat significant, I will make improvements in the v2 of the patchset. Thanks, Feiyang > > Thomas. > > -- > Crap can work. Given enough thrust pigs will fly, but it's not necessarily a > good idea. [ RFC1925, 2.3 ]
