Re: [PATCH v6 29/30] LoongArch: KVM: Enable kvm config and add the makefile

[Tianrui Zhao <zhaotianrui@xxxxxxxxxxx>]

在 2023年04月13日 16:33, Xi Ruoyao 写道:
> On Thu, 2023-04-13 at 15:32 +0800, kernel test robot wrote:
>
> > vim +/asm +244 arch/loongarch/include/asm/loongarch.h
> >
> > f2ac457a61389b Huacai Chen  2022-05-31  238
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  239  /* GCSR */
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  240  static inline u64 gcsr_read(u32 reg)
> Try __always_inline instead of inline because this "function" will
> definitely break up if it's not inlined.
>
> And I guess we should have something like:
>
> extern u64 __compiletime_error("gcsr_read parameter is not a constant")
> __gcsr_read_non_const(void);
>
> static __always_inline u64 gcsr_read(u32 reg)
> {
> 	u64 val = 0;
>
> 	if (!__builtin_constant_p(reg))
> 		return __gcsr_read_non_const();
>
> 	asm volatile (
> ... ...
>
> Or perhaps we should just rewrite gcsr_read to a macro.
>
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  241  {
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  242     u64 val = 0;
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  243     /* Instructions will be available in binutils later */
> > 2c87b678639d25 Tianrui Zhao 2023-04-12 @244     asm volatile (
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  245             "parse_r __reg, %[val]\n\t"
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  246             /*
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  247              * read val from guest csr register %[reg]
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  248              * gcsrrd %[val], %[reg]
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  249              */
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  250             ".word 0x5 << 24 | %[reg] << 10 | 0 << 5 | __reg\n\t"
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  251             : [val] "+r" (val)
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  252             : [reg] "i" (reg)
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  253             : "memory");
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  254
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  255     return val;
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  256  }
> > 2c87b678639d25 Tianrui Zhao 2023-04-12  257
Thanks, it really should use __always_inline there, and I will reconsider to fix this function mistakes about compiling.

Thanks
Tianrui Zhao