Re: [PATCH] x86/unaccepted_memory: Do not accept ranges that are no longer E820 RAM

["Gupta, Pankaj" <pankaj.gupta@amd.com>]

>>>> Can we just disallow memmap= when running in a confidential VM?
>>> My experiments showed: memmap itself don't have a problem but memap
>>> with a hole is causing crash.
>>>
>>> There might be some usecases which are already using this, e.g:
>>>
>>> https://lore.kernel.org/all/20261029-cma-multi-v1-0-2cbced8b5cb7@kernel.org/
>>>
>>>
>> Its also good to have a general safeguard to not accept memory that is
>> not marked as RAM in e820?
>>
> Personally, I think all these command line hacks should be avoided in
> confidential VMs, on the basis that the firmware's view of memory should
> be in sync with the OS.
Fair enough. I can post a separate on top RFC patch to disable memmap= 
holes completely
for confidential guests and see if anybody objects.

That said, this patch fixes a real crash with memmap= holes 
functionality in confidential guests today,
and should be backported to stable kernels as well. It also hardens the 
existing code to only accept the
e820 RAM regions.

Thanks for having a look!

Pankaj