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SubjectRe: [PATCH 1/4] kexec: reuse crash kernel reserved memory for normal kexec
Hi Albert,

On Mon, Jul 25, 2022 at 04:38:53PM +0800, Albert Huang wrote:
> The kexec userspace tool also needs to add parameter options(-r) that
> support the use of reserved memory (see another patch for kexec)
>
> [...]
>
> - if (kexec_on_panic) {
> + if (kexec_on_panic && kexec_on_reserved) {

Two small questions related to this:

- Why does kexec-tools need an option, or more specifically, why does
userspace need to communicate about this at all? Can't the kernel just
automatically use the available reserved memory in the case that's not
already being used by the panic handler kernel? I'm curious about
whether there are caveats that would make this occasionally
undesirable, hence suggesting an option.

- I don't totally understand how this works, so I might be a bit off
here, but is there any chance that this could be made to co-exist with
kexec_on_panic? Can a larger region just be reserved, specifically for
this, rather than piggy backing on the panic handler region?

> +static struct page *kimage_alloc_reserverd_control_pages(struct kimage *image,
> + case KEXEC_TYPE_RESERVED_MEM:
> + pages = kimage_alloc_reserverd_control_pages(image, order);

Nit:
reserverd -> reserved

Jason

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