Re: [PATCH 0/5] x86: Impplement support for unaccepted memory

On 8/9/21 11:26 PM, Kirill A. Shutemov wrote:

UEFI Specification version 2.9 introduces concept of memory acceptance:
Some Virtual Machine platforms, such as Intel TDX or AMD SEV-SNP,
requiring memory to be accepted before it can be used by the guest.
Accepting happens via a protocol specific for the Virtrual Machine
platform.

Accepting memory is costly and it makes VMM allocate memory for the
accepted guest physical address range. We don't want to accept all memory
upfront.

This could use a bit more explanation.  Any VM is likely to *eventually*
touch all its memory, so it's not like a VMM has a long-term advantage
by delaying this.

So, it must have to do with resource use at boot.  Is this to help boot
times?

I had expected this series, but I also expected it to be connected to
CONFIG_DEFERRED_STRUCT_PAGE_INIT somehow.  Could you explain a bit how
this problem is different and demands a totally orthogonal solution?

For instance, what prevents us from declaring: "Memory is accepted at
the time that its 'struct page' is initialized" ?  Then, we use all the
infrastructure we already have for DEFERRED_STRUCT_PAGE_INIT.

This series isn't too onerous, but I do want to make sure that we're not
reinventing the wheel.