linux-kernel - [PATCH Part2 RFC v2 24/37] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates

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Message-Id: <20210430123822.13825-25-brijesh.singh@amd.com>
Date:   Fri, 30 Apr 2021 07:38:09 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, bp@...en8.de, jroedel@...e.de,
        thomas.lendacky@....com, pbonzini@...hat.com, mingo@...hat.com,
        dave.hansen@...el.com, rientjes@...gle.com, seanjc@...gle.com,
        peterz@...radead.org, hpa@...or.com, tony.luck@...el.com,
        Brijesh Singh <brijesh.singh@....com>
Subject: [PATCH Part2 RFC v2 24/37] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates

The guest pages of the SEV-SNP VM maybe added as a private page in the
RMP entry (assigned bit is set). The guest private pages must be
transitioned to the hypervisor state before its freed.

Signed-off-by: Brijesh Singh <brijesh.singh@....com>
---
 arch/x86/kvm/svm/sev.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index d97f37df1f3b..4ce91c2583a3 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1920,6 +1920,45 @@ find_enc_region(struct kvm *kvm, struct kvm_enc_region *range)
 static void __unregister_enc_region_locked(struct kvm *kvm,
 					   struct enc_region *region)
 {
+	struct rmpupdate val = {};
+	unsigned long i, pfn;
+	struct rmpentry *e;
+	int level, rc;
+
+	/*
+	 * The guest memory pages are assigned in the RMP table. Unassign it
+	 * before releasing the memory.
+	 */
+	if (sev_snp_guest(kvm)) {
+		for (i = 0; i < region->npages; i++) {
+			pfn = page_to_pfn(region->pages[i]);
+
+			if (need_resched())
+				schedule();
+
+			e = snp_lookup_page_in_rmptable(region->pages[i], &level);
+			if (unlikely(!e))
+				continue;
+
+			/* If its not a guest assigned page then skip it. */
+			if (!rmpentry_assigned(e))
+				continue;
+
+			/* Is the page part of a 2MB RMP entry? */
+			if (level == PG_LEVEL_2M) {
+				val.pagesize = RMP_PG_SIZE_2M;
+				pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1);
+			} else {
+				val.pagesize = RMP_PG_SIZE_4K;
+			}
+
+			/* Transition the page to hypervisor owned. */
+			rc = rmpupdate(pfn_to_page(pfn), &val);
+			if (rc)
+				pr_err("Failed to release pfn 0x%lx ret=%d\n", pfn, rc);
+		}
+	}
+
 	sev_unpin_memory(kvm, region->pages, region->npages);
 	list_del(&region->list);
 	kfree(region);
-- 
2.17.1