Re: [patch V4 part 1 27/36] arm64: Prepare arch_nmi_enter() for recursion

Frederic Weisbecker
2020-05-15T21:31:18Z

On Fri, May 15, 2020 at 11:29:13PM +0200, Thomas Gleixner wrote:
> Thomas Gleixner <tglx@linutronix.de> writes:
>
> > From: Frederic Weisbecker <frederic@kernel.org>
>
> This changelog was very empty. Here is what Peter provided:
>
> When using nmi_enter() recursively, arch_nmi_enter() must also be recursion
> safe. In particular, it must be ensured that HCR_TGE is always set while in
> NMI context when in HYP mode, and be restored to it's former state when
> done.
>
> The current code fails this when interleaved wrong. Notably it overwrites
> the original hcr state on nesting.
>
> Introduce a nesting counter to make sure to store the original value.

Nice!

Thanks.