From: Jia He <justin.he@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Jia He <justin.he@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Ard Biesheuvel <ardb@kernel.org>, Marc Zyngier <maz@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Richard Henderson <richard.henderson@linaro.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Steven Price <steven.price@arm.com>,
Mark Brown <broonie@kernel.org>,
Cristian Marussi <cristian.marussi@arm.com>,
Gavin Shan <gshan@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Martin <Dave.Martin@arm.com>,
Mike Rapoport <rppt@kernel.org>
Subject: [RFC PATCH 0/2] Avoid booting stall caused by
Date: Wed, 13 Jan 2021 09:40:45 +0800 [thread overview]
Message-ID: <20210113014047.14371-1-justin.he@arm.com> (raw)
There is a 10s stall in idmap_kpti_install_ng_mappings when kernel boots
on a Ampere EMAG server.
Commit f992b4dfd58b ("arm64: kpti: Add ->enable callback to remap
swapper using nG mappings") updates the nG bit runtime if kpti is
required.
But things get worse if rodata=full in map_mem(). NO_BLOCK_MAPPINGS |
NO_CONT_MAPPINGS is required when creating pagetable mapping. Hence all
ptes are fully mapped in this case. On a Ampere EMAG server with 256G
memory(pagesize=4k), it causes the 10s stall.
After moving init_cpu_features() ahead of early_fixmap_init(), we can use
cpu_have_const_cap earlier than before. Hence we can avoid this stall
by updating arm64_use_ng_mappings.
After this patch series, it reduces the kernel boot time from 14.7s to
4.1s:
Before:
[ 14.757569] Freeing initrd memory: 60752K
After:
[ 4.138819] Freeing initrd memory: 60752K
Set it as RFC because I want to resolve any other points which I have
misconerned.
Jia He (2):
arm64/cpuinfo: Move init_cpu_features() ahead of early_fixmap_init()
arm64: kpti: Update arm64_use_ng_mappings before pagetable mapping
arch/arm64/include/asm/cpu.h | 1 +
arch/arm64/kernel/cpuinfo.c | 13 ++++++++++---
arch/arm64/kernel/setup.c | 18 +++++++++++++-----
arch/arm64/kernel/smp.c | 3 +--
4 files changed, 25 insertions(+), 10 deletions(-)
--
2.17.1
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next reply other threads:[~2021-01-13 1:44 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 1:40 Jia He [this message]
2021-01-13 1:40 ` [RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init() Jia He
2021-01-26 13:57 ` Will Deacon
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
2021-01-26 14:14 ` Will Deacon
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