Re: [PATCH v3 5/6] KVM: SEV: Perform RMP optimizations on SNP guest shutdown

[Dave Hansen]

On 3/30/26 15:27, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
> 
> As SNP guests are launched, pages converted to private cause RMPUPDATE
> to disable the corresponding RMPOPT optimizations.
> 
> Conversely, during SNP guest termination, when guest pages are
> converted back to shared and are not assigned, RMPOPT will be used
> to re-enable RMP optimizations.

This is all super passive. It makes it impossible to tell what is
background versus imperative voice on what the patch is doing.

	== Background / Problem ==

	Pages are converted from shared to private as SNP guests are
	launched. This destroys existing RMPOPT optimizations in the
	regions where pages are converted.

	Conversely, guest pages are converted back to shared during SNP
	guest termination and their region may become eligible for
	RMPOPT optimization.

	== Solution ==

	To take advantage of this, perform RMPOPT after guest
	termination. Do it after a delay so that a single RMPOPT pass
	can be done if multiple guests terminate in a short period of
	time.
	
With a fixed changelog:

Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

I'm just saying "ack" on this one because it's a pretty KVM-specific
thing about when the guest is destroyed to the point of being good for
RMPOPT. This needs many more eyeballs from the KVM folks than me.