From: Mark Rutland <mark.rutland@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Jia He <justin.he@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Anshuman Khandual <anshuman.khandual@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Richard Henderson <richard.henderson@linaro.org>,
Dave Martin <Dave.Martin@arm.com>,
Steven Price <steven.price@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
Gavin Shan <gshan@redhat.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Mark Brown <broonie@kernel.org>, Marc Zyngier <maz@kernel.org>,
Cristian Marussi <cristian.marussi@arm.com>
Subject: Re: [RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init()
Date: Tue, 26 Jan 2021 14:11:48 +0000 [thread overview]
Message-ID: <20210126141148.GC80448@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20210126135712.GA29956@willie-the-truck>
On Tue, Jan 26, 2021 at 01:57:13PM +0000, Will Deacon wrote:
> > @@ -297,16 +297,20 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
> > */
> > arm64_use_ng_mappings = kaslr_requires_kpti();
> >
> > - early_fixmap_init();
> > - early_ioremap_init();
> > -
> > - setup_machine_fdt(__fdt_pointer);
> > -
> > /*
> > * Initialise the static keys early as they may be enabled by the
> > * cpufeature code and early parameters.
> > */
> > jump_label_init();
>
> I don't think your patch changes this, but afaict jump_label_init() uses
> per-cpu variables via cpus_read_lock(), yet we don't initialise our offset
> until later on. Any idea how that works?
We initialize the boot CPU's offset twice during boot, once before this
in smp_setup_processor_id(), and once afterwards in
smp_prepare_boot_cpu() since setup_per_cpu_areas() will allocate a new
region for CPU0.
IIUC per-cpu writes before smp_prepare_boot_cpu() are potentially dodgy
since they might be copied to other CPUs, but reads are all fine.
Mark.
WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>,
Jia He <justin.he@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Richard Henderson <richard.henderson@linaro.org>,
linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Mark Brown <broonie@kernel.org>,
Cristian Marussi <cristian.marussi@arm.com>,
Mike Rapoport <rppt@kernel.org>, Marc Zyngier <maz@kernel.org>,
Gavin Shan <gshan@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Steven Price <steven.price@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init()
Date: Tue, 26 Jan 2021 14:11:48 +0000 [thread overview]
Message-ID: <20210126141148.GC80448@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20210126135712.GA29956@willie-the-truck>
On Tue, Jan 26, 2021 at 01:57:13PM +0000, Will Deacon wrote:
> > @@ -297,16 +297,20 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
> > */
> > arm64_use_ng_mappings = kaslr_requires_kpti();
> >
> > - early_fixmap_init();
> > - early_ioremap_init();
> > -
> > - setup_machine_fdt(__fdt_pointer);
> > -
> > /*
> > * Initialise the static keys early as they may be enabled by the
> > * cpufeature code and early parameters.
> > */
> > jump_label_init();
>
> I don't think your patch changes this, but afaict jump_label_init() uses
> per-cpu variables via cpus_read_lock(), yet we don't initialise our offset
> until later on. Any idea how that works?
We initialize the boot CPU's offset twice during boot, once before this
in smp_setup_processor_id(), and once afterwards in
smp_prepare_boot_cpu() since setup_per_cpu_areas() will allocate a new
region for CPU0.
IIUC per-cpu writes before smp_prepare_boot_cpu() are potentially dodgy
since they might be copied to other CPUs, but reads are all fine.
Mark.
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linux-arm-kernel@lists.infradead.org
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next prev parent reply other threads:[~2021-01-26 14:13 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 1:40 [RFC PATCH 0/2] Avoid booting stall caused by Jia He
2021-01-13 1:40 ` Jia He
2021-01-13 1:40 ` [RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init() Jia He
2021-01-13 1:40 ` Jia He
2021-01-26 13:57 ` Will Deacon
2021-01-26 13:57 ` Will Deacon
2021-01-26 14:11 ` Mark Rutland [this message]
2021-01-26 14:11 ` Mark Rutland
2021-01-13 1:40 ` [RFC PATCH 2/2] arm64: kpti: Update arm64_use_ng_mappings before pagetable mapping Jia He
2021-01-13 1:40 ` Jia He
2021-01-26 14:14 ` Will Deacon
2021-01-26 14:14 ` Will Deacon
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