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From: Ben Horgan <ben.horgan@arm.com>
To: Fuad Tabba <fuad.tabba@linux.dev>
Cc: "Will Deacon" <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, "Thomas Gleixner" <tglx@kernel.org>,
	"Ștefania Ion" <stefion@google.com>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Pankaj Patil" <pankaj.patil@oss.qualcomm.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Jinjie Ruan" <ruanjinjie@huawei.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Tarun Sahu" <tarunsahu@google.com>,
	"David Woodhouse" <dwmw@amazon.co.uk>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Marc Zyngier" <maz@kernel.org>
Subject: Re: [PATCH v2 08/23] arm64: cpufeature: Store every ID register with its overrides applied
Date: Mon, 12 Oct 2026 12:10:53 +0100	[thread overview]
Message-ID: <ded76345-d09f-44d1-8f62-1d9c6ebd4272@arm.com> (raw)
In-Reply-To: <CA+EHjTwgfGzS92thiGFcJ1NgoA732RBqv3gJUWF1gJAE-jANFA@mail.gmail.com>

Hi Fuad,

On 11/10/2026 08:34, Fuad Tabba wrote:
> Hi Ben,
> 
> On Fri, 09 Oct 2026 16:51:14 +0100, Ben Horgan <ben.horgan@arm.com> wrote:
> [...]
>>> the same way. Everything read with read_cpuid() goes through
>>> read_cpuid_with_overrides(). CTR_EL0 and CNTFRQ_EL0, which are read
> [...]
>> For completeness shouldn't read_cpuid(SMIDR_EL1) change to
>> read_cpuid_with_overrides(SMIDR_EL1)?
> 
> "Everything" should have said every register in arm64_ftr_regs[], and
> SMIDR_EL1 isn't one of them, so read_cpuid_with_overrides() would hit
> the WARN_ON() in get_arm64_ftr_reg() whenever SME is enabled.

Thanks for the explanation. If I understand correctly, SMIDR_EL1 isn't in arm64_ftr_regs[] because
there is no need to sanitize SMIDR_EL1 to give a consistent view across cpus. If and when support
for sme priority is added then a unified view of the SMIDR_EL1.HIP, highest implement priority,
would be needed and so at that point deserve a place in arm64_ftr_regs[].

Cheers,
Ben

> 
> Thanks,
> /fuad


  reply	other threads:[~2026-10-12 11:10 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-09 10:07 [PATCH v2 00/23] arm64: Implement parallel CPU onlining with PSCI v0.2+ Will Deacon
2026-10-09 10:07 ` [PATCH v2 01/23] cpu/hotplug: Clean up cmpxchg() logic in cpuhp_can_boot_ap() Will Deacon
2026-10-09 10:07 ` [PATCH v2 02/23] cpu/hotplug: Avoid trying to bring up CPUs that are already online Will Deacon
2026-10-09 10:07 ` [PATCH v2 03/23] cpu/hotplug: Avoid busy-polling on archs where cpu_relax() is a no-op Will Deacon
2026-10-09 10:46   ` David Woodhouse
2026-10-09 11:07     ` Will Deacon
2026-10-09 10:07 ` [PATCH v2 04/23] cpu/hotplug: Propagate bring-up status to arch_cpuhp_cleanup_kick_cpu() Will Deacon
2026-10-09 10:07 ` [PATCH v2 05/23] arm64: cpufeature: Check arm64_ftr_regs[] before the first store Will Deacon
2026-10-10  2:49   ` Jinjie Ruan
2026-10-09 10:07 ` [PATCH v2 06/23] arm64: cpufeature: Add read_cpuid_with_overrides() Will Deacon
2026-10-09 10:07 ` [PATCH v2 07/23] arm64: cpufeature: Read MPAMIDR_EL1 in __cpuinfo_store_cpu() Will Deacon
2026-10-09 15:44   ` Ben Horgan
2026-10-09 10:07 ` [PATCH v2 08/23] arm64: cpufeature: Store every ID register with its overrides applied Will Deacon
2026-10-09 15:51   ` Ben Horgan
2026-10-11  7:34     ` Fuad Tabba
2026-10-12 11:10       ` Ben Horgan [this message]
2026-10-09 10:07 ` [PATCH v2 09/23] arm64: smp: Tidy up smp_prepare_cpus() Will Deacon
2026-10-09 10:07 ` [PATCH v2 10/23] arm64: smp: Tidy up cpuinfo init and cpufeature updates Will Deacon
2026-10-09 10:07 ` [PATCH v2 11/23] arm64: smp: Defer update of secondary CPU capabilities Will Deacon
2026-10-09 10:07 ` [PATCH v2 12/23] arm64: smp: Don't bother printing the I-cache policy for each CPU Will Deacon
2026-10-09 10:07 ` [PATCH v2 13/23] arm64: smp: Defer RCU registration during secondary CPU bringup Will Deacon
2026-10-09 10:07 ` [PATCH v2 14/23] arm64: smp: Use generic HOTPLUG_CORE_SYNC_FULL machinery for CPU onlining Will Deacon
2026-10-09 10:07 ` [PATCH v2 15/23] arm64: smp: Use generic HOTPLUG_SPLIT_STARTUP " Will Deacon
2026-10-09 10:07 ` [PATCH v2 16/23] arm64: cpu_ops: Make 'cpu_operations' pointer global instead of per-cpu Will Deacon
2026-10-09 10:07 ` [PATCH v2 17/23] arm64: cpu_ops: Introduce get_secondary_cpu_ops() Will Deacon
2026-10-09 10:07 ` [PATCH v2 18/23] firmware/psci: Cache PSCI v0.2+ version number to avoid redundant SMCs Will Deacon
2026-10-09 10:07 ` [PATCH v2 19/23] firmware/psci: Extend ->cpu_on() callback to take an additional argument Will Deacon
2026-10-09 10:07 ` [PATCH v2 20/23] arm64: cpu_ops: Expose optional argument to target cpu in ->cpu_boot() Will Deacon
2026-10-09 10:07 ` [PATCH v2 21/23] arm64: smp: Pass secondary CPU boot parameters via firmware if possible Will Deacon
2026-10-09 10:07 ` [PATCH v2 22/23] arm64: smp: Use generic HOTPLUG_PARALLEL machinery for CPU onlining Will Deacon
2026-10-09 10:07 ` [PATCH v2 23/23] arm64: smp: Harden parallel CPU bringup against broken PSCI firmware Will Deacon
2026-10-11  1:43 ` [PATCH v2 00/23] arm64: Implement parallel CPU onlining with PSCI v0.2+ Michael Kelley
2026-10-12 13:35 ` Jinjie Ruan

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