Re: [PATCHv6 09/16] x86/mm: Adding callbacks to prepare encrypted memory for kexec

[Nikolay Borisov]

On 24.01.24 г. 14:55 ч., Kirill A. Shutemov wrote:
> AMD SEV and Intel TDX guests allocate shared buffers for performing I/O.
> This is done by allocating pages normally from the buddy allocator and
> then converting them to shared using set_memory_decrypted().
>
> On kexec, the second kernel is unaware of which memory has been
> converted in this manner. It only sees E820_TYPE_RAM. Accessing shared
> memory as private is fatal.
>
> Therefore, the memory state must be reset to its original state before
> starting the new kernel with kexec.
>
> The process of converting shared memory back to private occurs in two
> steps:
>
> - enc_kexec_stop_conversion() stops new conversions.
>
> - enc_kexec_unshare_mem() unshares all existing shared memory, reverting
>    it back to private.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>