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Re: [PATCH v4 16/28] arm64/sve: Probe SVE capabilities and usable vector lengths
- From: Catalin Marinas <catalin dot marinas at arm dot com>
- To: Dave Martin <Dave dot Martin at arm dot com>
- Cc: linux-arm-kernel at lists dot infradead dot org, linux-arch at vger dot kernel dot org, Okamoto Takayuki <tokamoto at jp dot fujitsu dot com>, libc-alpha at sourceware dot org, Ard Biesheuvel <ard dot biesheuvel at linaro dot org>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, Will Deacon <will dot deacon at arm dot com>, Alex Bennée <alex dot bennee at linaro dot org>, kvmarm at lists dot cs dot columbia dot edu
- Date: Fri, 27 Oct 2017 13:56:22 +0100
- Subject: Re: [PATCH v4 16/28] arm64/sve: Probe SVE capabilities and usable vector lengths
- Authentication-results: sourceware.org; auth=none
- References: <1509101470-7881-1-git-send-email-Dave.Martin@arm.com> <1509101470-7881-17-git-send-email-Dave.Martin@arm.com>
On Fri, Oct 27, 2017 at 11:50:58AM +0100, Dave P Martin wrote:
> This patch uses the cpufeatures framework to determine common SVE
> capabilities and vector lengths, and configures the runtime SVE
> support code appropriately.
>
> ZCR_ELx is not really a feature register, but it is convenient to
> use it as a template for recording the maximum vector length
> supported by a CPU, using the LEN field. This field is similar to
> a feature field in that it is a contiguous bitfield for which we
> want to determine the minimum system-wide value. This patch adds
> ZCR as a pseudo-register in cpuinfo/cpufeatures, with appropriate
> custom code to populate it. Finding the minimum supported value of
> the LEN field is left to the cpufeatures framework in the usual
> way.
>
> The meaning of ID_AA64ZFR0_EL1 is not architecturally defined yet,
> so for now we just require it to be zero.
>
> Note that much of this code is dormant and SVE still won't be used
> yet, since system_supports_sve() remains hardwired to false.
>
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>