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Date: Tue, 3 Apr 2018 13:45:18 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v9 15/24] mm: Introduce __vm_normal_page()
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References: <1520963994-28477-1-git-send-email-ldufour@linux.vnet.ibm.com> <1520963994-28477-16-git-send-email-ldufour@linux.vnet.ibm.com> <20180403193927.GD5935@redhat.com>
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To: Jerome Glisse <jglisse@redhat.com>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>, paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox <willy@infradead.org>, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, hpa@zytor.com, Will Deacon <will.deacon@arm.com>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Andrea Arcangeli <aarcange@redhat.com>, Alexei Starovoitov <alexei.starovoitov@gmail.com>, kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com, Daniel Jordan <daniel.m.jordan@oracle.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen <tim.c.chen@linux.intel.com>, linuxppc-dev@lists.ozlabs.org, x86@kernel.org

On Tue, 3 Apr 2018, Jerome Glisse wrote:

> > When dealing with the speculative fault path we should use the VMA's field
> > cached value stored in the vm_fault structure.
> > 
> > Currently vm_normal_page() is using the pointer to the VMA to fetch the
> > vm_flags value. This patch provides a new __vm_normal_page() which is
> > receiving the vm_flags flags value as parameter.
> > 
> > Note: The speculative path is turned on for architecture providing support
> > for special PTE flag. So only the first block of vm_normal_page is used
> > during the speculative path.
> 
> Might be a good idea to explicitly have SPECULATIVE Kconfig option depends
> on ARCH_PTE_SPECIAL and a comment for !HAVE_PTE_SPECIAL in the function
> explaining that speculative page fault should never reach that point.

Yeah, I think that's appropriate but in a follow-up patch since this is 
only propagating vma_flags.  It will require that __HAVE_ARCH_PTE_SPECIAL 
become an actual Kconfig entry, however.