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Message-ID: <f58814e156b918531f058acfac944abef34f5fb1.camel@wdc.com>
Date: Tue, 13 Aug 2019 00:15:15 +0000
From: Atish Patra <Atish.Patra@....com>
To: "hch@...radead.org" <hch@...radead.org>
CC: "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
Anup Patel <Anup.Patel@....com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"paul.walmsley@...ive.com" <paul.walmsley@...ive.com>,
"aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"allison@...utok.net" <allison@...utok.net>,
"alexios.zavras@...el.com" <alexios.zavras@...el.com>,
"palmer@...ive.com" <palmer@...ive.com>
Subject: Re: [PATCH] RISC-V: Issue a local tlb flush if possible.
On Mon, 2019-08-12 at 07:56 -0700, Christoph Hellwig wrote:
> I agree with the comment that we really should move this out of line
> now, and
sure.
> also that we can simplify it further, which also includes
> not bothering with the SBI call if we were the only online CPU.
I already had that optimization in my patch.
> I also thing we need to use get_cpu/put_cpu to be preemption safe.
>
ok. I will update that.
> Also why would we need to do a local flush if we have a mask that
> doesn't include the local CPU?
>
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 about something like:
>
> void __riscv_flush_tlb(struct cpumask *cpumask, unsigned long start,
> unsigned long size)
> {
> unsigned int cpu;
>
> if (!cpumask)
> cpumask = cpu_online_mask;
>
> cpu = get_cpu();
> 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.
Regards,
Atish
> }
>
> if (!cpumask_empty(cpumask)) {
> struct cpumask hmask;
>
> riscv_cpuid_to_hartid_mask(cpumask, &hmask);
> sbi_remote_sfence_vma(hmask.bits, start, size);
> }
> put_cpu();
> }
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