[PATCH v9 6/6] KVM: SEV: Perform RMP optimizations on SNP guest shutdown

[Ashish Kalra]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

Pages are converted from shared to private as SNP guests are launched.
This destroys exisiting 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.

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.

Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e107f368ed2d..23e236b13ccd 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3005,6 +3005,16 @@ void sev_vm_destroy(struct kvm *kvm)
 		 */
 		if (snp_decommission_context(kvm))
 			return;
+
+		/*
+		 * 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.
+		 */
+		snp_rmpopt_all_physmem();
 	} else {
 		sev_unbind_asid(kvm, sev->handle);
 	}
-- 
2.43.0