Re: [PATCH v5 0/2] nosnp sev command line support

[Dave Hansen]

On 9/30/24 16:11, Pavan Kumar Paluri wrote:
> Provide "nosnp" boot option via "sev=nosnp" kernel command line to
> prevent SEV-SNP[1] capable host kernel from enabling SEV-SNP and
> initializing Reverse Map Table (RMP) [1].
> 
> On providing sev=nosnp via kernel command line:
> cat /sys/module/kvm_amd/parameters/sev_snp should be "N".

I don't see any mention in the changelog, cover letter or Documentation/
about why someone would want to do this.

I assume it's because of performance (walking the RMP table is non-zero
cost).

The BIOS allocates the RMP table, right?  So this option presumably gets
the performance back, but not the memory.  That's probably also worth
mentioning ... somewhere.