From: Will Deacon <will@kernel.org>
To: Jia He <justin.he@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
James Morse <james.morse@arm.com>, Marc Zyngier <maz@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Suzuki Poulose <Suzuki.Poulose@arm.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
hejianet@gmail.com, Kaly Xin <Kaly.Xin@arm.com>,
nd@arm.com
Subject: Re: [PATCH v12 0/4] fix double page fault in cow_user_page for pfn mapping
Date: Tue, 15 Oct 2019 01:18:34 +0100 [thread overview]
Message-ID: <20191015001834.wwkd46t6dwicta7n@willie-the-truck> (raw)
In-Reply-To: <20191011140939.6115-1-justin.he@arm.com>
On Fri, Oct 11, 2019 at 10:09:35PM +0800, Jia He wrote:
> When we tested pmdk unit test vmmalloc_fork TEST1 in arm64 guest, there
> will be a double page fault in __copy_from_user_inatomic of cow_user_page.
>
> As told by Catalin: "On arm64 without hardware Access Flag, copying from
> user will fail because the pte is old and cannot be marked young. So we
> always end up with zeroed page after fork() + CoW for pfn mappings. we
> don't always have a hardware-managed access flag on arm64."
>
> -Changes
> v12:
> refine PATCH 01, remove the !! since C languages can convert unsigned
> to bool (Catalin)
Thanks. I think it's a bit late to take something like this for 5.4 now,
especially as the current behaviour has always been there. Hopefully
somebody can queue it for 5.5 instead.
Will
next prev parent reply other threads:[~2019-10-15 0:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-11 14:09 [PATCH v12 0/4] fix double page fault in cow_user_page for pfn mapping Jia He
2019-10-11 14:09 ` [PATCH v12 1/4] arm64: cpufeature: introduce helper cpu_has_hw_af() Jia He
2019-10-11 14:09 ` [PATCH v12 2/4] arm64: mm: implement arch_faults_on_old_pte() on arm64 Jia He
2019-10-11 14:09 ` [PATCH v12 3/4] x86/mm: implement arch_faults_on_old_pte() stub on x86 Jia He
2019-10-11 14:09 ` [PATCH v12 4/4] mm: fix double page fault on arm64 if PTE_AF is cleared Jia He
2019-10-15 0:18 ` Will Deacon [this message]
2019-10-16 14:32 ` [PATCH v12 0/4] fix double page fault in cow_user_page for pfn mapping Catalin Marinas
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