Re: [PATCH] RISC-V: Issue a local tlb flush if possible.

[hch@xxxxxxxxxxxxx]

On Tue, Aug 13, 2019 at 12:15:15AM +0000, Atish Patra wrote:
> I thought if it recieves an empty cpumask, then it should at least do a
> local flush is the expected behavior. Are you saying that we should
> just skip all and return ? 

How could we ever receive an empty cpu mask?  I think it could only
be empty without the current cpu.  At least that is my reading of
the callers and a few other implementations.

> > 	if (!cpumask || cpumask_test_cpu(cpu, cpumask) {
> > 		if ((start == 0 && size == -1) || size > PAGE_SIZE)
> > 			local_flush_tlb_all();
> > 		else if (size == PAGE_SIZE)
> > 			local_flush_tlb_page(start);
> > 		cpumask_clear_cpu(cpuid, cpumask);
> 
> This will modify the original cpumask which is not correct. clear part
> has to be done on hmask to avoid a copy.

Indeed.  But looking at the x86 tlbflush implementation it seems like we
could use cpumask_any_but() to avoid having to modify the passed in
cpumask.