Date: Wed, 21 Jun 2017 12:27:02 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>, Vineet Gupta <vgupta@synopsys.com>,
        Russell King <linux@armlinux.org.uk>,
        Will Deacon <will.deacon@arm.com>, Ralf Baechle <ralf@linux-mips.org>,
        "David S. Miller" <davem@davemloft.net>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Andrea Arcangeli <aarcange@redhat.com>, linux-arch@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCHv2 1/3] x86/mm: Provide pmdp_establish() helper
Message-ID: <20170621112702.GC10220@e104818-lin.cambridge.arm.com>
References: <20170615145224.66200-1-kirill.shutemov@linux.intel.com>
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 <20170619152228.GE3024@e104818-lin.cambridge.arm.com>
 <20170619160005.wgj4nymtj2nntfll@node.shutemov.name>
 <20170619170911.GF3024@e104818-lin.cambridge.arm.com>
 <20170619215210.2crwjou3sfdcj73d@node.shutemov.name>
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On Wed, Jun 21, 2017 at 12:53:03PM +0300, Kirill A. Shutemov wrote:
> > > > > > On Thu, Jun 15, 2017 at 05:52:22PM +0300, Kirill A. Shutemov wrote:
> > > > > > > We need an atomic way to setup pmd page table entry, avoiding races with
> > > > > > > CPU setting dirty/accessed bits. This is required to implement
> > > > > > > pmdp_invalidate() that doesn't loose these bits.
[...]
> Any chance you could help me with arm too?

On arm (ARMv7 with LPAE) we don't have hardware updates of the
access/dirty bits, so a generic implementation would suffice. I didn't
find one in your patches, so here's an untested version:

static inline pmd_t pmdp_establish(struct mm_struct *mm, unsigned long address,
				   pmd_t *pmdp, pmd_t pmd)
{
	pmd_t old_pmd = *pmdp;
	set_pmd_at(mm, address, pmdp, pmd);
	return old_pmd;
}

-- 
Catalin