From: Catalin Marinas <catalin.marinas@arm.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Jia He" <justin.he@arm.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Ralph Campbell" <rcampbell@nvidia.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Peter Zijlstra" <peterz@infradead.org>,
"Dave Airlie" <airlied@redhat.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
"Thomas Hellstrom" <thellstrom@vmware.com>,
"Souptick Joarder" <jrdr.linux@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm: fix double page fault on arm64 if PTE_AF is cleared
Date: Tue, 10 Sep 2019 10:15:15 +0100 [thread overview]
Message-ID: <20190910091515.GE14442@C02TF0J2HF1T.local> (raw)
In-Reply-To: <20190906145742.GX29434@bombadil.infradead.org>
On Fri, Sep 06, 2019 at 07:57:42AM -0700, Matthew Wilcox wrote:
> On Fri, Sep 06, 2019 at 09:57:47PM +0800, Jia He wrote:
> > * This really shouldn't fail, because the page is there
> > * in the page tables. But it might just be unreadable,
> > * in which case we just give up and fill the result with
> > - * zeroes.
> > + * zeroes. If PTE_AF is cleared on arm64, it might
> > + * cause double page fault. So makes pte young here
>
> How about:
> * zeroes. On architectures with software "accessed" bits,
> * we would take a double page fault here, so mark it
> * accessed here.
>
> > */
> > + if (!pte_young(vmf->orig_pte)) {
>
> Let's guard this with:
>
> if (arch_sw_access_bit && !pte_young(vmf->orig_pte)) {
>
> #define arch_sw_access_bit 0
> by default and have arm64 override it (either to a variable or a constant
> ... your choice). Also, please somebody decide on a better name than
> arch_sw_access_bit.
I'm not good at names either (is arch_faults_on_old_pte any better?) but
I'd make this a 0 args call: arch_sw_access_bit(). This way we can make
it a static inline function on arm64 with some static label check.
--
Catalin
next prev parent reply other threads:[~2019-09-10 9:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-06 13:57 [PATCH v2] mm: fix double page fault on arm64 if PTE_AF is cleared Jia He
2019-09-06 14:57 ` Matthew Wilcox
2019-09-10 9:15 ` Catalin Marinas [this message]
2019-09-09 21:27 ` Matthew Wilcox
2019-09-10 9:08 ` Catalin Marinas
2019-09-10 9:29 ` Kirill A. Shutemov
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