Re: RFC x86/boot/64: BOOT_PGT_SIZE definition for compressed kernel

[Joerg Roedel]

On Tue, Oct 27, 2020 at 03:40:07PM +0300, Kirill A. Shutemov wrote:
> BTW, what happens if we underestimate BOOT_PGT_SIZE? Do we overwrite
> something?

The boot code will print an error and stop the machine when allocating a
page-table page fails.

I also think that bumping BOOT_PGT_SIZE up to have more pages available
is a good short-term solution. Recycling pages will also need to take
page encryption attributes into account, as for SEV-ES the GHCB page
needs to be mapped unencrypted.

Another option to safe some memory is to make use of GB pages in the
decompression code. Machines where the current BOOT_PGT_SIZE is too
small will likely support GB pages too.

Regards,

	Joerg