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SubjectRe: [patch 2/2] x86/mm/pti: Do not invoke PTI functions when PTI is disabled

* Thomas Gleixner <tglx@linutronix.de> wrote:

> When PTI is disabled at boot time either because the CPU is not affected or
> PTI has been disabled on the command line, the boot code still calls into
> pti_finalize() which then unconditionally invokes:
>
> pti_clone_entry_text()
> pti_clone_kernel_text()
>
> pti_clone_kernel_text() was called unconditionally before the 32bit support
> was added and 32bit added the call to pti_clone_entry_text().
>
> The call has no side effects as cloning the page tables into the available
> second one, which was allocated for PTI does not create damage. But it does
> not make sense either and in case that this functionality would be extended
> later this might actually lead to hard to diagnose issue.

s/issue/issues

> Neither function should be called when PTI is runtime disabled. Make the
> invocation conditional.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/x86/mm/pti.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> --- a/arch/x86/mm/pti.c
> +++ b/arch/x86/mm/pti.c
> @@ -668,6 +668,8 @@ void __init pti_init(void)
> */
> void pti_finalize(void)
> {
> + if (!boot_cpu_has(X86_FEATURE_PTI))
> + return;
> /*
> * We need to clone everything (again) that maps parts of the
> * kernel image.

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

Ingo

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