Re: [PATCH v4 5/5] riscv: implement IPI-based remote TLB shootdown

[Christoph Hellwig <hch@infradead.org>]

On Wed, Mar 27, 2019 at 12:41:30AM +0000, Gary Guo wrote:
> From: Gary Guo <gary@garyguo.net>
> 
> This patch implements IPI-based remote TLB shootdown, which is useful
> at this stage for testing because BBL/OpenSBI ignores operands of
> sbi_remote_sfence_vma_asid and always perform a global TLB flush.
> The SBI-based remote TLB shootdown can still be opt-in using boot
> cmdline "tlbi_method=sbi".

I think Anup now fixes OpenSBI.  Do you have benchmarks vs BBL,
old OpenSBI and new OpenSBI?

> +static void ipi_remote_sfence_vma(void *info)
> +{
> +	struct tlbi *data = info;
> +	unsigned long start = data->start;
> +	unsigned long size = data->size;
> +	unsigned long i;
> +
> +	if (size == SFENCE_VMA_FLUSH_ALL) {
> +		local_flush_tlb_all();
> +	}

Doesn't this need a return to skip the latter code?  Also it might
we worth to just split the all case into entirely separate helpers,
that way the on_each_cpu calls don't need to pass a private data
argument at all.

> +
> +	for (i = 0; i < size; i += PAGE_SIZE) {
> +		__asm__ __volatile__ ("sfence.vma %0"
> +				      : : "r" (start + i)
> +				      : "memory");
> +	}

local_flush_tlb_kernel_page?

> +static void ipi_remote_sfence_vma_asid(void *info)
> +{
> +	struct tlbi *data = info;
> +	unsigned long asid = data->asid;
> +	unsigned long start = data->start;
> +	unsigned long size = data->size;
> +	unsigned long i;
> +
> +	if (size == SFENCE_VMA_FLUSH_ALL) {
> +		__asm__ __volatile__ ("sfence.vma x0, %0"
> +				      : : "r" (asid)
> +				      : "memory");
> +		return;
> +	}
> +
> +	for (i = 0; i < size; i += PAGE_SIZE) {
> +		__asm__ __volatile__ ("sfence.vma %0, %1"
> +				      : : "r" (start + i), "r" (asid)
> +				      : "memory");
> +	}

local_flush_tlb_range?

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