[PATCH RFC v9 45/51] KVM: SEV: Implement gmem hook for invalidating private pages

[Michael Roth]

Implement a platform hook to do the work of restoring the direct map
entries of gmem-managed pages and transitioning the corresponding RMP
table entries back to the default shared/hypervisor-owned state.

Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 43 ++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c |  1 +
 arch/x86/kvm/svm/svm.h |  1 +
 3 files changed, 45 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index c5a1706387bf..543926fa3200 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4117,3 +4117,46 @@ int sev_gmem_prepare(struct kvm *kvm, struct kvm_memory_slot *slot,
 
 	return rc;
 }
+
+void sev_gmem_invalidate(struct kvm *kvm, kvm_pfn_t start, kvm_pfn_t end)
+{
+	kvm_pfn_t pfn;
+
+	if (!sev_snp_guest(kvm))
+		return;
+
+	pr_debug("%s: kvm %p pfn 0x%llx pfn_end 0x%llx\n",
+		 __func__, kvm, start, end);
+
+	for (pfn = start; pfn < end; pfn++) {
+		int rc, rmp_level;
+		bool assigned;
+
+		rc = snp_lookup_rmpentry(pfn, &assigned, &rmp_level);
+		if (rc) {
+			pr_warn_ratelimited("SEV: Failed to retrieve RMP entry for PFN 0x%llx error %d\n",
+					    pfn, rc);
+			continue;
+		}
+
+		if (!assigned)
+			continue;
+
+		/*
+		 * If PFN is currently assigned as a 2M page, PSMASH it into
+		 * individual 4K RMP entries before attempting to convert a
+		 * 4K sub-page.
+		 */
+		if (rmp_level > PG_LEVEL_4K) {
+			rc = snp_rmptable_psmash(kvm, pfn);
+			if (rc)
+				pr_warn_ratelimited("SEV: Failed to PSMASH RMP entry for PFN 0x%llx error %d\n",
+						    pfn, rc);
+		}
+
+		rc = rmp_make_shared(pfn, PG_LEVEL_4K);
+		if (rc)
+			pr_warn_ratelimited("SEV: Failed to update RMP entry for PFN 0x%llx error %d\n",
+					    pfn, rc);
+	}
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9085a122907c..1390e47d0aa5 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4936,6 +4936,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.alloc_apic_backing_page = svm_alloc_apic_backing_page,
 
 	.gmem_prepare = sev_gmem_prepare,
+	.gmem_invalidate = sev_gmem_invalidate,
 };
 
 /*
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 0438f52e4396..0d4c29a4300a 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -772,6 +772,7 @@ void handle_rmp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code);
 void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu);
 int sev_gmem_prepare(struct kvm *kvm, struct kvm_memory_slot *slot,
 		     kvm_pfn_t pfn, gfn_t gfn, u8 *max_level);
+void sev_gmem_invalidate(struct kvm *kvm, kvm_pfn_t start, kvm_pfn_t end);
 
 /* vmenter.S */
 
-- 
2.25.1