Re: [PATCH V3 2/2] riscv: Use use_asid_allocator flush TLB

Guo Ren
2021-05-26T03:13:13Z

On Tue, May 25, 2021 at 8:35 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Tue, May 25, 2021 at 12:24:07PM +0000, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > Use static_branch_unlikely(&use_asid_allocator) to keep the origin
> > tlb flush style, so it's no effect on the existing machine. Here
> > are the optimized functions:
> > - flush_tlb_mm
> > - flush_tlb_page
> > - flush_tlb_range
> >
> > All above are based on the below new implement functions:
> > - __sbi_tlb_flush_range_asid
> > - local_flush_tlb_range_asid
>
>
> This mentiones what functions you're changing, but not what the
> substantial change is, and more importantly why you change it.
>
> > +static inline void local_flush_tlb_range_asid(unsigned long start, unsigned long size,
> > + unsigned long asid)
>
> Crazy long line. Should be:
>
> static inline void local_flush_tlb_range_asid(unsigned long start,
> unsigned long size, unsigned long asid)
>
> > +{
> > + unsigned long tmp = start & PAGE_MASK;
> > + unsigned long end = ALIGN(start + size, PAGE_SIZE);
> > +
> > + if (size == -1) {
> > + __asm__ __volatile__ ("sfence.vma x0, %0" : : "r" (asid) : "memory");
> > + return;
>
> Please split the global (size == -1) case into separate helpers.
Do you mean:
if (size == -1) {
__asm__ __volatile__ ("sfence.vma x0, %0"
:
: "r" (asid)
: "memory");
} else {
for (tmp = start & PAGE_MASK; tmp < end; tmp += PAGE_SIZE) {
__asm__ __volatile__ ("sfence.vma %0, %1"
:
: "r" (tmp), "r" (asid)
: "memory");
tmp += PAGE_SIZE;
}
}

>
> > + while(tmp < end) {
>
> Missing whitespace befre the (.
>
> Also I think this would read nicer as:
>
> for (tmp = start & PAGE_MASK; tmp < end; tmp += PAGE_SIZE)
>
> > +static void __sbi_tlb_flush_range_asid(struct cpumask *cmask, unsigned long start,
> > + unsigned long size, unsigned long asid)
>
> Another overly long line.
>
> Also for all thee __sbi_* functions, why the __ prefix?
I just follow the previous coding convention by __sbi_tlb_flush_range.
If you don't like it, I think it should be another coding convention
patchset.
This patchset is only to add the functions of tlb_flush_with_asid.

>
> > + if (cpumask_any_but(cmask, cpuid) >= nr_cpu_ids) {
> > + local_flush_tlb_range_asid(start, size, asid);
> > + } else {
> > + riscv_cpuid_to_hartid_mask(cmask, &hmask);
> > + sbi_remote_sfence_vma_asid(cpumask_bits(&hmask), start, size, asid);
>
> Another long line (and a few more later).

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/