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

[Song Liu]

> On Aug 28, 2019, at 7:24 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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.
> 
> Neither function should be called when PTI is runtime disabled. Make the
> invocation conditional.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Acked-by: Song Liu <songliubraving@xxxxxx>