Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation

[Catalin Marinas <catalin.marinas@arm.com>]

On Tue, Jul 05, 2022 at 06:02:02PM +0300, Mike Rapoport wrote:
> +void __init remap_crashkernel(void)
> +{
> +#ifdef CONFIG_KEXEC_CORE
> +	phys_addr_t start, end, size;
> +	phys_addr_t aligned_start, aligned_end;
> +
> +	if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
> +	    return;
> +
> +	if (!crashk_res.end)
> +	    return;
> +
> +	start = crashk_res.start & PAGE_MASK;
> +	end = PAGE_ALIGN(crashk_res.end);
> +
> +	aligned_start = ALIGN_DOWN(crashk_res.start, PUD_SIZE);
> +	aligned_end = ALIGN(end, PUD_SIZE);
> +
> +	/* Clear PUDs containing crash kernel memory */
> +	unmap_hotplug_range(__phys_to_virt(aligned_start),
> +			    __phys_to_virt(aligned_end), false, NULL);

What I don't understand is what happens if there's valid kernel data
between aligned_start and crashk_res.start (or the other end of the
range).

-- 
Catalin