From: Will Deacon <will.deacon@arm.com>
To: Julien Grall <julien.grall@arm.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
gdb@sourceware.org, "Alan Hayward" <alan.hayward@arm.com>,
"Zhang Lei" <zhang.lei@jp.fujitsu.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Dave Martin" <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/3] arm64/sve: Fix missing SVE/FPSIMD endianness conversions
Date: Thu, 13 Jun 2019 10:22:47 +0100 [thread overview]
Message-ID: <20190613092247.GD17331@fuggles.cambridge.arm.com> (raw)
In-Reply-To: <771b0099-9217-4e55-b73a-b03434c61655@arm.com>
On Wed, Jun 12, 2019 at 06:46:04PM +0100, Julien Grall wrote:
> On 12/06/2019 17:00, Dave Martin wrote:
> > The in-memory representation of SVE and FPSIMD registers is
> > different: the FPSIMD V-registers are stored as single 128-bit
> > host-endian values, whereas SVE registers are stored in an
> > endianness-invariant byte order.
> >
> > This means that the two representations differ when running on a
> > big-endian host. But we blindly copy data from one representation
> > to another when converting between the two, resulting in the
> > register contents being unintentionally byteswapped in certain
> > situations. Currently this can be triggered by the first SVE
> > instruction after a syscall, for example (though the potential
> > trigger points may vary in future).
> >
> > So, fix the conversion functions fpsimd_to_sve(), sve_to_fpsimd()
> > and sve_sync_from_fpsimd_zeropad() to swab where appropriate.
> >
> > There is no common swahl128() or swab128() that we could use here.
> > Maybe it would be worth making this generic, but for now add a
> > simple local hack.
> >
> > Since the byte order differences are exposed in ABI, also clarify
> > the docuentation.
>
> NIT: s/docuentation/documentation/
>
> Although, it is probably too late to fix this one as Will already took the patch.
I actually spotted (and fixed) that one when I committed the patch, but I
missed the others. Given that this is top of the fixes branch, I can
probably just fold these in.
Will
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next prev parent reply other threads:[~2019-06-13 9:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-12 16:00 [PATCH v2 0/3] arm64/sve: Fix mutating register endianness on big-endian Dave Martin
2019-06-12 16:00 ` [PATCH v2 1/3] arm64/sve: Fix missing SVE/FPSIMD endianness conversions Dave Martin
2019-06-12 17:28 ` Will Deacon
2019-06-27 13:51 ` Catalin Marinas
2019-06-27 15:18 ` Dave Martin
2019-06-12 17:46 ` Julien Grall
2019-06-13 9:22 ` Will Deacon [this message]
2019-06-13 10:00 ` Dave Martin
2019-06-13 10:17 ` Will Deacon
2019-06-13 10:20 ` Dave Martin
2019-06-12 16:00 ` [PATCH v2 2/3] arm64/sve: Factor out FPSIMD to SVE state conversion Dave Martin
2019-06-20 13:45 ` Julien Grall
2019-07-22 10:31 ` Catalin Marinas
2019-06-12 16:00 ` [PATCH v2 3/3] arm64/sve: Fix a couple of magic numbers for the Z-reg count Dave Martin
2019-06-20 13:43 ` Julien Grall
2019-07-22 10:32 ` Catalin Marinas
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