Date: Wed, 21 Jun 2017 15:04:12 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Catalin Marinas <catalin.marinas@arm.com>
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: <20170621120412.cdmg76jy2zby56cx@node.shutemov.name>
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On Wed, Jun 21, 2017 at 12:27:02PM +0100, Catalin Marinas wrote:
> 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;
> }

Thanks, I'll integrate this into the patchset.

-- 
 Kirill A. Shutemov