From: Will Deacon <will@kernel.org>
To: James Morse <james.morse@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
Russell King <linux@armlinux.org.uk>,
Ard Biesheuvel <ardb@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: [PATCH v2 0/2] ARM/arm64: errata: Remove AES hwcap for 32bit tasks on A57/A72
Date: Wed, 20 Apr 2022 11:15:23 +0100 [thread overview]
Message-ID: <20220420101523.GA7286@willie-the-truck> (raw)
In-Reply-To: <20220413170545.3042558-1-james.morse@arm.com>
On Wed, Apr 13, 2022 at 06:05:43PM +0100, James Morse wrote:
> Hello,
>
> These patches remove the AES HWCAP on A57 and A72 for aarch32 user-space
> processes due to erratum #1742098 and #1655431. An interrupt between two
> instructions will cause these parts to get the wrong result.
> These extensions are optional, so software should have a fallback
> implementation.
>
> The 32bit patch is new for v2, as Ard points out the behaviour should
> be the same here.
>
> Operating on the HWCAP bitmap directly avoids affecting KVM, which
> was the problem with v1. But it does mean HWCAP_PMULL is still visible
> to aarch32 processes. This isn't affected by the erratum, but is detected
> from the same field in the ID register. PMULL is value '2', AES is value '1'.
> User-space would be crazy to let PMULL imply AES, right ...
That seems like a completely sensible thing for userspace to do :/
The Arm ARM states:
AES, bits [7:4]
Indicates support for AES instructions in AArch64 state. Defined values are:
0b0000 No AES instructions implemented.
0b0001 AESE, AESD, AESMC, and AESIMC instructions implemented.
0b0010 As for 0b0001 , plus PMULL/PMULL2 instructions operating on 64-bit data quantities.
So PMULL is defined to include AES.
Will
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prev parent reply other threads:[~2022-04-20 10:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-13 17:05 [PATCH v2 0/2] ARM/arm64: errata: Remove AES hwcap for 32bit tasks on A57/A72 James Morse
2022-04-13 17:05 ` [PATCH v2 1/2] arm64: errata: Remove AES hwcap for COMPAT tasks James Morse
2022-04-13 17:33 ` Ard Biesheuvel
2022-04-14 17:45 ` James Morse
2022-04-14 10:03 ` Will Deacon
2022-04-14 17:43 ` James Morse
2022-04-20 10:17 ` Will Deacon
2022-07-14 16:05 ` James Morse
2022-04-13 17:05 ` [PATCH v2 2/2] ARM: Remove AES hwcap for parts affected by errata James Morse
2022-04-13 17:34 ` Ard Biesheuvel
2022-04-13 18:15 ` Russell King (Oracle)
2022-04-20 10:15 ` Will Deacon [this message]
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