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SubjectRe: [RFC PATCH] arm64: fix the missing ktpi= cmdline check in arm64_kernel_unmapped_at_el0()
[Adding Catalin and LAKML]

Mark.

On Tue, Mar 17, 2020 at 07:47:08PM +0800, Hongbo Yao wrote:
> Kpti cannot be disabled from the kernel cmdline after the commit
> 09e3c22a("arm64: Use a variable to store non-global mappings decision").
>
> Bring back the missing check of kpti= command-line option to fix the
> case where the SPE driver complains the missing "kpti-off" even it has
> already been set.
>
> Signed-off-by: Hongbo Yao <yaohongbo@huawei.com>
> ---
> arch/arm64/include/asm/mmu.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
> index 3c9533322558..ebbc0d3ac2f7 100644
> --- a/arch/arm64/include/asm/mmu.h
> +++ b/arch/arm64/include/asm/mmu.h
> @@ -34,7 +34,8 @@ extern bool arm64_use_ng_mappings;
>
> static inline bool arm64_kernel_unmapped_at_el0(void)
> {
> - return arm64_use_ng_mappings;
> + return arm64_use_ng_mappings &&
> + cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0);
> }
>
> typedef void (*bp_hardening_cb_t)(void);
> --
> 2.20.1
>

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