From: Will Deacon <will.deacon@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Zi Yan <zi.yan@cs.rutgers.edu>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kirill.shutemov@linux.intel.com, akpm@linux-foundation.org,
mhocko@suse.com, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Subject: Re: [PATCH] mm/thp: Correctly differentiate between mapped THP and PMD migration entry
Date: Tue, 6 Nov 2018 00:35:10 +0000 [thread overview]
Message-ID: <20181106003509.GA27283@brain-police> (raw)
In-Reply-To: <9d9aaf03-617a-d383-7d59-8b98fdd3c1e7@arm.com>
On Fri, Nov 02, 2018 at 11:45:00AM +0530, Anshuman Khandual wrote:
> On 10/17/2018 07:39 AM, Andrea Arcangeli wrote:
> > What we need to do during split is an invalidate of the huge TLB.
> > There's no pmd_trans_splitting anymore, so we only clear the present
> > bit in the PTE despite pmd_present still returns true (just like
> > PROT_NONE, nothing new in this respect). pmd_present never meant the
>
> On arm64, the problem is that pmd_present() is tied with pte_present() which
> checks for PTE_VALID (also PTE_PROT_NONE) but which gets cleared during PTE
> invalidation. pmd_present() returns false just after the first step of PMD
> splitting. So pmd_present() needs to be decoupled from PTE_VALID which is
> same as PMD_SECT_VALID and instead should depend upon a pte bit which sticks
> around like PAGE_PSE as in case of x86. I am working towards a solution.
Could we not just go via a PROT_NONE mapping during the split, instead of
having to allocate a new software bit to treat these invalid ptes as
present?
Will
next prev parent reply other threads:[~2018-11-06 0:35 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-09 3:58 [PATCH] mm/thp: Correctly differentiate between mapped THP and PMD migration entry Anshuman Khandual
2018-10-09 13:04 ` Kirill A. Shutemov
2018-10-09 13:18 ` Will Deacon
2018-10-12 8:02 ` Anshuman Khandual
2018-10-15 8:32 ` Aneesh Kumar K.V
2018-10-16 13:16 ` Anshuman Khandual
2018-10-09 13:42 ` Anshuman Khandual
2018-10-09 13:58 ` Zi Yan
2018-10-10 4:05 ` Anshuman Khandual
2018-10-10 12:43 ` Zi Yan
2018-10-12 8:00 ` Anshuman Khandual
2018-10-15 0:53 ` Zi Yan
2018-10-15 4:06 ` Anshuman Khandual
2018-10-16 14:31 ` Zi Yan
2018-10-18 2:17 ` Naoya Horiguchi
2018-11-02 5:22 ` Anshuman Khandual
2018-10-25 8:10 ` Anshuman Khandual
2018-10-25 18:45 ` Zi Yan
2018-10-26 1:39 ` Anshuman Khandual
2018-10-17 2:09 ` Andrea Arcangeli
2018-10-22 14:00 ` Zi Yan
2018-11-02 6:15 ` Anshuman Khandual
2018-11-06 0:35 ` Will Deacon [this message]
2018-11-06 9:51 ` Anshuman Khandual
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