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From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: bhsharma@redhat.com, linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, Steve.Capper@arm.com,
	catalin.marinas@arm.com, ard.biesheuvel@linaro.org,
	will.deacon@arm.com, bhupesh.linux@gmail.com,
	kexec@lists.infradead.org
Subject: Re: [PATCH 1/2] arm64: Expose address bits (physical/virtual) via cpuinfo
Date: Tue, 29 Jan 2019 10:09:31 +0000
Message-ID: <afa2417a-10d0-21f6-007f-e8eb7055f3d7@arm.com> (raw)
In-Reply-To: <1548709076-22317-2-git-send-email-bhsharma@redhat.com>

Hi Bupesh

On 28/01/2019 20:57, Bhupesh Sharma wrote:
> With ARMv8.2-LVA and LPA architecture extensions, arm64 hardware which
> supports these extensions can support upto 52-bit virtual and 52-bit
> physical addresses respectively.
> 
> Since at the moment we enable the support of these extensions via CONFIG
> flags, e.g.
>   - LPA via CONFIG_ARM64_PA_BITS_52, and
>   - LVA via CONFIG_ARM64_FORCE_52BIT
> 
> The easiest way a user can determine the physical/virtual
> addresses supported on the hardware, is via the '/proc/cpuinfo'
> interface.

Why do we need this information ?

Btw, this keeps coming up all the time and the answer to this approach is
always no. We cannot break the "unwritten" ABI of /proc/cpuinfo, again.
See :

https://patchwork.kernel.org/patch/8669301/


Suzuki

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Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-28 20:57 [PATCH 0/2] arm64: Expose physical and virtual address capabilities to user-space Bhupesh Sharma
2019-01-28 20:57 ` [PATCH 1/2] arm64: Expose address bits (physical/virtual) via cpuinfo Bhupesh Sharma
2019-01-29 10:09   ` Suzuki K Poulose [this message]
2019-01-30 19:48     ` Bhupesh Sharma
2019-02-04 16:54       ` James Morse
2019-01-28 20:57 ` [PATCH 2/2] arm64: Expose PARange via ID_AA64MMFR0_EL1 and VARange via ID_AA64MMFR2_EL1 Bhupesh Sharma
2019-01-29 10:14   ` Suzuki K Poulose
2019-01-30 20:27     ` Bhupesh Sharma

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