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

Christoph Hellwig
2021-05-25T12:36:19Z

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.

> + 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?

> + 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).