Re: [RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init()

2021-01-26 Thread Mark Rutland 
On Tue, Jan 26, 2021 at 01:57:13PM +, 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.

Re: [RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init()

2021-01-26 Thread Will Deacon 
On Wed, Jan 13, 2021 at 09:40:46AM +0800, Jia He wrote:
> Move init_cpu_features() ahead of setup_arch()->early_fixmap_init(), which
> is the preparation work for checking the condition to assign
> arm64_use_ng_mappings as cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0).
> 
> Besides, jump_label_init() is also moved ahead because
> cpus_have_const_cap() depends on static key enable api.
> 
> Percpu helpers should be avoided in cpuinfo_store_boot_cpu() before percpu
> init at main.c::setup_per_cpu_areas()
> 
> Signed-off-by: Jia He 
> ---
>  arch/arm64/include/asm/cpu.h |  1 +
>  arch/arm64/kernel/cpuinfo.c  | 13 ++---
>  arch/arm64/kernel/setup.c| 14 +-
>  arch/arm64/kernel/smp.c  |  3 +--
>  4 files changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
> index 7faae6ff3ab4..59f36f5e3c04 100644
> --- a/arch/arm64/include/asm/cpu.h
> +++ b/arch/arm64/include/asm/cpu.h
> @@ -63,6 +63,7 @@ DECLARE_PER_CPU(struct cpuinfo_arm64, cpu_data);
>  
>  void cpuinfo_store_cpu(void);
>  void __init cpuinfo_store_boot_cpu(void);
> +void __init save_boot_cpuinfo_data(void);
>  
>  void __init init_cpu_features(struct cpuinfo_arm64 *info);
>  void update_cpu_features(int cpu, struct cpuinfo_arm64 *info,
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 77605aec25fe..f8de5b8bae20 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -413,9 +413,16 @@ void cpuinfo_store_cpu(void)
>  
>  void __init cpuinfo_store_boot_cpu(void)
>  {
> - struct cpuinfo_arm64 *info = _cpu(cpu_data, 0);
> - __cpuinfo_store_cpu(info);
> + __cpuinfo_store_cpu(_cpu_data);
>  
> - boot_cpu_data = *info;
>   init_cpu_features(_cpu_data);
>  }
> +
> +void __init save_boot_cpuinfo_data(void)
> +{
> + struct cpuinfo_arm64 *info;
> +
> + set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
> + info = _cpu(cpu_data, 0);
> + *info = boot_cpu_data;
> +}
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 1a57a76e1cc2..e078ab068f3b 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -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?

Will

[RFC PATCH 1/2] arm64/cpuinfo: Move init_cpu_features() ahead of setup.c::early_fixmap_init()

2021-01-12 Thread Jia He 
Move init_cpu_features() ahead of setup_arch()->early_fixmap_init(), which
is the preparation work for checking the condition to assign
arm64_use_ng_mappings as cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0).

Besides, jump_label_init() is also moved ahead because
cpus_have_const_cap() depends on static key enable api.

Percpu helpers should be avoided in cpuinfo_store_boot_cpu() before percpu
init at main.c::setup_per_cpu_areas()

Signed-off-by: Jia He 
---
 arch/arm64/include/asm/cpu.h |  1 +
 arch/arm64/kernel/cpuinfo.c  | 13 ++---
 arch/arm64/kernel/setup.c| 14 +-
 arch/arm64/kernel/smp.c  |  3 +--
 4 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
index 7faae6ff3ab4..59f36f5e3c04 100644
--- a/arch/arm64/include/asm/cpu.h
+++ b/arch/arm64/include/asm/cpu.h
@@ -63,6 +63,7 @@ DECLARE_PER_CPU(struct cpuinfo_arm64, cpu_data);
 
 void cpuinfo_store_cpu(void);
 void __init cpuinfo_store_boot_cpu(void);
+void __init save_boot_cpuinfo_data(void);
 
 void __init init_cpu_features(struct cpuinfo_arm64 *info);
 void update_cpu_features(int cpu, struct cpuinfo_arm64 *info,
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 77605aec25fe..f8de5b8bae20 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -413,9 +413,16 @@ void cpuinfo_store_cpu(void)
 
 void __init cpuinfo_store_boot_cpu(void)
 {
-   struct cpuinfo_arm64 *info = _cpu(cpu_data, 0);
-   __cpuinfo_store_cpu(info);
+   __cpuinfo_store_cpu(_cpu_data);
 
-   boot_cpu_data = *info;
init_cpu_features(_cpu_data);
 }
+
+void __init save_boot_cpuinfo_data(void)
+{
+   struct cpuinfo_arm64 *info;
+
+   set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
+   info = _cpu(cpu_data, 0);
+   *info = boot_cpu_data;
+}
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 1a57a76e1cc2..e078ab068f3b 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -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();
+
+   /* Init the cpu feature codes for boot cpu */
+   cpuinfo_store_boot_cpu();
+
+   early_fixmap_init();
+   early_ioremap_init();
+
+   setup_machine_fdt(__fdt_pointer);
+
parse_early_param();
 
/*
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 2499b895efea..3df1f5b1da0b 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -449,8 +449,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 
 void __init smp_prepare_boot_cpu(void)
 {
-   set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
-   cpuinfo_store_boot_cpu();
+   save_boot_cpuinfo_data();
 
/*
 * We now know enough about the boot CPU to apply the
-- 
2.17.1