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SubjectRe: [RFC v2 4/5] x86/crash: make the page that stores the LUKS volume key inaccessible
Hi Dave,

Thanks for the quick review!

On Fri, Nov 04, 2022 at 07:38:17AM -0700, Dave Hansen wrote:
>On 11/4/22 04:29, Coiby Xu wrote:
>> + if (kexec_crash_image->luks_volume_key_addr) {
>> + start = kexec_crash_image->luks_volume_key_addr;
>> + end = start + kexec_crash_image->luks_volume_key_sz - 1;
>> + page = pfn_to_page(start >> PAGE_SHIFT);
>> + nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
>> + set_memory_np((unsigned long)page_address(page), nr_pages);
>> + }
>
>Why does this go pfn -> page -> vaddr? What good does having the page
>do?

Sorry it's an imitation of kexec_mark_crashkres.

> Can you just do phys_to_virt() on the start address? Maybe:
>
> start_paddr = kexec_crash_image->luks_volume_key_addr;
> end_paddr = start_paddr + kexec_crash_image->luks_volume_key_sz - 1;
> nr_pages = (PAGE_ALIGN(end_paddr) - PAGE_ALIGN_DOWN(start_paddr))/
>PAGE_SIZE;
> set_memory_np((unsigned long)phys_to_virt(start_paddr), nr_pages);

Thanks for suggesting a smarter implementation! I'll apply it to next
version.

>
>Also, if you resend this, please just cc the x86 folks on the series.
>The other patches and cover letter have desperately needed context
>around this.

Sure, I'll cc the x86 list the complete patch set next time. Sorry
you'll have to go to
https://lore.kernel.org/lkml/20221104113000.487098-5-coxu@redhat.com/t/
to read related emails for now.


>

--
Best regards,
Coiby

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