Re: [PATCHv9 09/17] x86/mm: Adding callbacks to prepare encrypted memory for kexec

["Huang, Kai" <kai.huang@intel.com>]

On 25/03/2024 11:39 pm, 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@linux.intel.com>
> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>x
> ---

Reviewed-by: Kai Huang <kai.huang@intel.com>