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Date:   Mon, 19 Aug 2019 08:10:17 -0700
From:   "hch@infradead.org" <hch@infradead.org>
To:     Anup Patel <anup@brainfault.org>
Cc:     "hch@infradead.org" <hch@infradead.org>,
        Atish Patra <Atish.Patra@wdc.com>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        Anup Patel <Anup.Patel@wdc.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "alexios.zavras@intel.com" <alexios.zavras@intel.com>,
        "palmer@sifive.com" <palmer@sifive.com>,
        "paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "allison@lohutok.net" <allison@lohutok.net>
Subject: Re: [PATCH] RISC-V: Issue a local tlb flush if possible.
Message-ID: <20190819151015.GA3316@infradead.org>
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On Mon, Aug 19, 2019 at 08:39:02PM +0530, Anup Patel wrote:
> If we were using ASID then yes we don't need to flush anything
> but currently we don't use ASID due to lack of HW support and
> HW can certainly do speculatively page table walks so flushing
> local TLB when MM mask is empty might help.
> 
> This just my theory and we need to stress test more.

Well, when we context switch away from a mm we always flush the
local tlb.  So either the mm_struct has never been scheduled in,
or we alrady did a local_tlb_flush and we context switched it up.