Hi,
Kindly ping 😊
> -----Original Message-----
> From: Jia He <[email protected]>
> Sent: Wednesday, January 13, 2021 9:41 AM
> To: Catalin Marinas <[email protected]>; Will Deacon
> <[email protected]>; [email protected]; linux-
> [email protected]
> Cc: Anshuman Khandual <[email protected]>; Suzuki Poulose
> <[email protected]>; Justin He <[email protected]>; Mark Rutland
> <[email protected]>; Gustavo A. R. Silva <[email protected]>;
> Richard Henderson <[email protected]>; Dave P Martin
> <[email protected]>; Steven Price <[email protected]>; Andrew Morton
> <[email protected]>; Mike Rapoport <[email protected]>; Ard
> Biesheuvel <[email protected]>; Gavin Shan <[email protected]>; Kefeng Wang
> <[email protected]>; Mark Brown <[email protected]>; Marc Zyngier
> <[email protected]>; Cristian Marussi <[email protected]>
> Subject: [RFC PATCH 0/2] Avoid booting stall caused by
>
> 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
