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From: Andrea della Porta <aporta@suse.de>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mark.rutland@arm.com
Subject: Re: [PATCH v2 1/4] arm64: Introduce aarch32_enabled()
Date: Wed, 15 Nov 2023 16:36:24 +0100	[thread overview]
Message-ID: <ZVTleETzfFUchs77@apocalypse> (raw)
In-Reply-To: <e13d8d85-67d7-4a5e-893c-69dacb3a6d24@arm.com>

On 12:56 Tue 24 Oct     , Robin Murphy wrote:
> On 23/10/2023 3:42 pm, Andrea della Porta wrote:
> > Aarch32 bit support on 64bit kernels depends on whether CONFIG_COMPAT
> > is selected or not. As it is a compile time option it doesn't
> > provide the flexibility to have distributions set their own policy for
> > Aarch32 support and give the user the flexibility to override it.
> > 
> > As a first step introduce aarch32_enabled() which abstracts whether 32
> > bit compat is turned on or off. Upcoming patches will implement
> > the ability to set Aarch32 compat state at boot time.
> 
> Other than patch #3, which as previously mentioned should be unnecessary if
> the kernel correctly never starts an "unsupported" AArch32 process to begin
> with, what does this do that simply overriding ID_AA64PFR0_EL1.EL0 via the
> existing idreg-override mechanism wouldn't?
> 
> Thanks,
> Robin

You're right, I guess we can simpluy leverage system_supports_32bit_el0()
calling id_aa64pfr0_32bit_el0() and override the el0 nibble from command line,
instead of inventing a new kernel parameter. For the sake of simplicity,
maybe we can add a new alias in idreg-override, something like 'arm64.no32bit-el0'.

Thanks,
Andrea

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WARNING: multiple messages have this Message-ID (diff)
From: Andrea della Porta <aporta@suse.de>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mark.rutland@arm.com
Subject: Re: [PATCH v2 1/4] arm64: Introduce aarch32_enabled()
Date: Wed, 15 Nov 2023 16:36:24 +0100	[thread overview]
Message-ID: <ZVTleETzfFUchs77@apocalypse> (raw)
In-Reply-To: <e13d8d85-67d7-4a5e-893c-69dacb3a6d24@arm.com>

On 12:56 Tue 24 Oct     , Robin Murphy wrote:
> On 23/10/2023 3:42 pm, Andrea della Porta wrote:
> > Aarch32 bit support on 64bit kernels depends on whether CONFIG_COMPAT
> > is selected or not. As it is a compile time option it doesn't
> > provide the flexibility to have distributions set their own policy for
> > Aarch32 support and give the user the flexibility to override it.
> > 
> > As a first step introduce aarch32_enabled() which abstracts whether 32
> > bit compat is turned on or off. Upcoming patches will implement
> > the ability to set Aarch32 compat state at boot time.
> 
> Other than patch #3, which as previously mentioned should be unnecessary if
> the kernel correctly never starts an "unsupported" AArch32 process to begin
> with, what does this do that simply overriding ID_AA64PFR0_EL1.EL0 via the
> existing idreg-override mechanism wouldn't?
> 
> Thanks,
> Robin

You're right, I guess we can simpluy leverage system_supports_32bit_el0()
calling id_aa64pfr0_32bit_el0() and override the el0 nibble from command line,
instead of inventing a new kernel parameter. For the sake of simplicity,
maybe we can add a new alias in idreg-override, something like 'arm64.no32bit-el0'.

Thanks,
Andrea

  reply	other threads:[~2023-11-15 15:36 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-23 14:42 [PATCH v2 0/4] arm64: Make Aarch32 compatibility enablement optional at boot Andrea della Porta
2023-10-23 14:42 ` Andrea della Porta
2023-10-23 14:42 ` [PATCH v2 1/4] arm64: Introduce aarch32_enabled() Andrea della Porta
2023-10-23 14:42   ` Andrea della Porta
2023-10-24 11:56   ` Robin Murphy
2023-10-24 11:56     ` Robin Murphy
2023-11-15 15:36     ` Andrea della Porta [this message]
2023-11-15 15:36       ` Andrea della Porta
2023-10-23 14:42 ` [PATCH v2 2/4] arm64/process: Make loading of 32bit processes depend on aarch32_enabled() Andrea della Porta
2023-10-23 14:42   ` Andrea della Porta
2023-10-23 14:42 ` [PATCH v2 3/4] arm64/entry-common: Make Aarch32 exceptions' availability " Andrea della Porta
2023-10-23 14:42   ` Andrea della Porta
2023-10-25 11:27   ` Mark Rutland
2023-10-25 11:27     ` Mark Rutland
2023-11-15 16:09     ` Andrea della Porta
2023-11-15 16:09       ` Andrea della Porta
2023-10-23 14:42 ` [PATCH v2 4/4] arm64: Make Aarch32 support boot time configurable Andrea della Porta
2023-10-23 14:42   ` Andrea della Porta

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