linux-kernel - [PATCH RFC v7 57/64] KVM: SEV: Handle restricted memory invalidations for SNP

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Date:   Wed, 14 Dec 2022 13:40:49 -0600
From:   Michael Roth <michael.roth@....com>
To:     <kvm@...r.kernel.org>
CC:     <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
        <linux-crypto@...r.kernel.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <jroedel@...e.de>, <thomas.lendacky@....com>,
        <hpa@...or.com>, <ardb@...nel.org>, <pbonzini@...hat.com>,
        <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <jmattson@...gle.com>, <luto@...nel.org>,
        <dave.hansen@...ux.intel.com>, <slp@...hat.com>,
        <pgonda@...gle.com>, <peterz@...radead.org>,
        <srinivas.pandruvada@...ux.intel.com>, <rientjes@...gle.com>,
        <dovmurik@...ux.ibm.com>, <tobin@....com>, <bp@...en8.de>,
        <vbabka@...e.cz>, <kirill@...temov.name>, <ak@...ux.intel.com>,
        <tony.luck@...el.com>, <marcorr@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <alpergun@...gle.com>, <dgilbert@...hat.com>, <jarkko@...nel.org>,
        <ashish.kalra@....com>, <harald@...fian.com>
Subject: [PATCH RFC v7 57/64] KVM: SEV: Handle restricted memory invalidations for SNP

Implement a platform hook to do the work of restoring the direct map
entries and cleaning up RMP table entries for restricted memory that is
being freed back to the host.

Signed-off-by: Michael Roth <michael.roth@....com>
---
 arch/x86/kvm/svm/sev.c | 64 ++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c |  1 +
 arch/x86/kvm/svm/svm.h |  1 +
 3 files changed, 66 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0dd3d9debe48..8783b64557e5 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4557,3 +4557,67 @@ int sev_update_mem_attr(struct kvm_memory_slot *slot, unsigned int attr,
 
 	return 0;
 }
+
+void sev_invalidate_private_range(struct kvm_memory_slot *slot, gfn_t start, gfn_t end)
+{
+	gfn_t gfn = start;
+
+	if (!sev_snp_guest(slot->kvm))
+		return;
+
+	if (!kvm_slot_can_be_private(slot)) {
+		pr_warn_ratelimited("SEV: Memslot for GFN: 0x%llx is not private.\n",
+				    gfn);
+		return;
+	}
+
+	while (gfn < end) {
+		gpa_t gpa = gfn_to_gpa(gfn);
+		int level = PG_LEVEL_4K;
+		int order, rc;
+		kvm_pfn_t pfn;
+
+		if (!kvm_mem_is_private(slot->kvm, gfn)) {
+			gfn++;
+			continue;
+		}
+
+		rc = kvm_restricted_mem_get_pfn(slot, gfn, &pfn, &order);
+		if (rc) {
+			pr_warn_ratelimited("SEV: Failed to retrieve restricted PFN for GFN 0x%llx, rc: %d\n",
+					    gfn, rc);
+			gfn++;
+			continue;
+		}
+
+		if (order) {
+			int rmp_level;
+
+			if (IS_ALIGNED(gpa, page_level_size(PG_LEVEL_2M)) &&
+			    gpa + page_level_size(PG_LEVEL_2M) <= gfn_to_gpa(end))
+				level = PG_LEVEL_2M;
+			else
+				pr_debug("%s: GPA 0x%llx is not aligned to 2M, skipping 2M directmap restoration\n",
+					 __func__, gpa);
+
+			/* TODO: It may still be possible to restore 2M mapping here, but keep it simple for now. */
+			if (level == PG_LEVEL_2M &&
+			    (!snp_lookup_rmpentry(pfn, &rmp_level) || rmp_level == PG_LEVEL_4K)) {
+				pr_debug("%s: PFN 0x%llx is not mapped as 2M private range, skipping 2M directmap restoration\n",
+					 __func__, pfn);
+				level = PG_LEVEL_4K;
+			}
+		}
+
+		pr_debug("%s: GPA %llx PFN %llx order %d level %d\n",
+			 __func__, gpa, pfn, order, level);
+		rc = snp_make_page_shared(slot->kvm, gpa, pfn, level);
+		if (rc)
+			pr_err("SEV: Failed to restore page to shared, GPA: 0x%llx PFN: 0x%llx order: %d rc: %d\n",
+			       gpa, pfn, order, rc);
+
+		gfn += page_level_size(level) >> PAGE_SHIFT;
+		put_page(pfn_to_page(pfn));
+		cond_resched();
+	}
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 6cf5b73f74c1..543261c87eb3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4873,6 +4873,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 
 	.rmp_page_level_adjust = sev_rmp_page_level_adjust,
 	.update_mem_attr = sev_update_mem_attr,
+	.invalidate_restricted_mem = sev_invalidate_private_range,
 };
 
 /*
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 5f315225ae4d..277f53c903c2 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -743,6 +743,7 @@ 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_update_mem_attr(struct kvm_memory_slot *slot, unsigned int attr,
 			gfn_t start, gfn_t end);
+void sev_invalidate_private_range(struct kvm_memory_slot *slot, gfn_t start, gfn_t end);
 
 int sev_fault_is_private(struct kvm *kvm, gpa_t gpa, u64 error_code, bool *private_fault);
 
-- 
2.25.1