Re: [PATCHv2 1/3] x86/mm: Provide pmdp_establish() helper

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
Date: Wed, 21 Jun 2017 15:04:12 +0300	[thread overview]
Message-ID: <20170621120412.cdmg76jy2zby56cx@node.shutemov.name> (raw)
In-Reply-To: <20170621112702.GC10220@e104818-lin.cambridge.arm.com>

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