Re: [PATCH v13 5/5] x86/sev: Re-enable RMP optimizations on SNP guest shutdown

[Borislav Petkov]

On Wed, Sep 02, 2026 at 09:29:21PM +0000, Ashish Kalra wrote:
> +		/*
> +		 * Perform RMP optimizations on memory freed by terminating
> +		 * guests.  The scan is deferred, so it normally runs after
> +		 * sev_gmem_invalidate() has converted this guest's pages back to
> +		 * shared, and picks them up then.  A very large guest whose
> +		 * conversion has not finished by then is picked up by a later
> +		 * teardown's scan.
> +		 */

Move that comment over the function definition.

> +/*
> + * Delay, in milliseconds, before the RMP re-optimization pass runs after an
> + * SNP guest is torn down.  snp_rmpopt_all_physmem() re-arms the delayed work
> + * with mod_delayed_work() on each teardown, so the pass fires this long after
> + * the last teardown.  This coalesces a burst of teardowns into a single scan
> + * and gives each guest's pages time to be converted back to the shared,
> + * hypervisor-owned state before the scan re-optimizes their 1GB regions.  The
> + * 10 second value is a heuristic trading re-optimization latency against
> + * scanning too eagerly.
> + */

Simplify:

"Delay, in milliseconds, before the RMP re-optimization pass runs after an SNP
guest is torn down, passed as the delay to mod_delayed_work(). This coalesces
a burst of teardowns into a single scan and gives each guest's pages time to
be converted back to the shared, hypervisor-owned state. The 10 second value
is a heuristic trading re-optimization latency against scanning too eagerly."


> +#define RMPOPT_WORK_TIMEOUT	(10 * MSEC_PER_SEC)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette