[PATCH] arm64: kpti: Use early_param for kpti= command-line option

[PATCH] arm64: kpti: Use early_param for kpti= command-line option

[Will Deacon]

We inspect __kpti_forced early on as part of the cpufeature enable
callback which remaps the swapper page table using non-global entries.

Ensure that __kpti_forced has been updated to reflect the kpti=
command-line option before we start using it.

Reported-by: Wei Xu <xuwei5@hisilicon.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/cpufeature.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index d2856b129097..112b071e793f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -937,7 +937,7 @@ static int __init parse_kpti(char *str)
 	__kpti_forced = enabled ? 1 : -1;
 	return 0;
 }
-__setup("kpti=", parse_kpti);
+early_param("kpti=", parse_kpti);
 #endif	/* CONFIG_UNMAP_KERNEL_AT_EL0 */
 
 #ifdef CONFIG_ARM64_HW_AFDBM
-- 
2.1.4

[PATCH] arm64: kpti: Use early_param for kpti= command-line option

[Catalin Marinas]

On Wed, Jun 20, 2018 at 04:23:47PM +0100, Will Deacon wrote:
> We inspect __kpti_forced early on as part of the cpufeature enable
> callback which remaps the swapper page table using non-global entries.
> 
> Ensure that __kpti_forced has been updated to reflect the kpti=
> command-line option before we start using it.
> 
> Reported-by: Wei Xu <xuwei5@hisilicon.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Does it need a fixes tag?

Fixes: ea1e3de85e94 ("arm64: entry: Add fake CPU feature for unmapping the kernel at EL0")

-- 
Catalin

[PATCH] arm64: kpti: Use early_param for kpti= command-line option

[Will Deacon]

On Wed, Jun 20, 2018 at 04:40:32PM +0100, Catalin Marinas wrote:
> On Wed, Jun 20, 2018 at 04:23:47PM +0100, Will Deacon wrote:
> > We inspect __kpti_forced early on as part of the cpufeature enable
> > callback which remaps the swapper page table using non-global entries.
> > 
> > Ensure that __kpti_forced has been updated to reflect the kpti=
> > command-line option before we start using it.
> > 
> > Reported-by: Wei Xu <xuwei5@hisilicon.com>
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
> 
> Does it need a fixes tag?
> 
> Fixes: ea1e3de85e94 ("arm64: entry: Add fake CPU feature for unmapping the kernel at EL0")

Perhaps, but really this is just a performance optimisation for the kpti=off
case where we don't actually need to put the nG mappings down.

Will

[PATCH] arm64: kpti: Use early_param for kpti= command-line option

[Wei Xu]

Hi Will,

On 2018/6/20 16:23, Will Deacon wrote:
> We inspect __kpti_forced early on as part of the cpufeature enable
> callback which remaps the swapper page table using non-global entries.
> 
> Ensure that __kpti_forced has been updated to reflect the kpti=
> command-line option before we start using it.
> 
> Reported-by: Wei Xu <xuwei5@hisilicon.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/kernel/cpufeature.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index d2856b129097..112b071e793f 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -937,7 +937,7 @@ static int __init parse_kpti(char *str)
>  	__kpti_forced = enabled ? 1 : -1;
>  	return 0;
>  }
> -__setup("kpti=", parse_kpti);
> +early_param("kpti=", parse_kpti);

%s/kpti=/kpti

Thanks!

Best Regards,
Wei

>  #endif	/* CONFIG_UNMAP_KERNEL_AT_EL0 */
>  
>  #ifdef CONFIG_ARM64_HW_AFDBM
>