Re: [PATCH RFC v9 07/51] x86/sev: Add the host SEV-SNP initialization support

[Dave Hansen]

On 6/21/23 02:15, Borislav Petkov wrote:
> On Mon, Jun 12, 2023 at 08:34:02AM -0700, Dave Hansen wrote:
>> On 6/11/23 21:25, Michael Roth wrote:
>>> +	/*
>>> +	 * Calculate the amount the memory that must be reserved by the BIOS to
>>> +	 * address the whole RAM, including the bookkeeping area. The RMP itself
>>> +	 * must also be covered.
>>> +	 */
>>> +	max_rmp_pfn = max_pfn;
>>> +	if (PHYS_PFN(rmp_end) > max_pfn)
>>> +		max_rmp_pfn = PHYS_PFN(rmp_end);
>> Could you say a little here about how this deals with memory hotplug?
> Does SNP hw even support memory hotplug?
> 
> I think in order to support that, you'd need some special dance because
> of the RMP table etc...

Yep, there's the hardware side and then there are fun nuggets like using
mem= and then doing a software-only hot-add later after boot.

Also, if the hardware doesn't support any kind of hotplug, it would be
great to point to the place in the spec where it says that.