[PATCH 19/30] KVM: arm64: Annotate guest donations with handle and gfn in host stage-2

[Will Deacon]

Handling host kernel faults arising from accesses to donated guest
memory will require an rmap-like mechanism to identify the guest mapping
of the faulting page.

Extend the page donation logic to encode the guest handle and gfn
alongside the owner information in the host stage-2 pte.

Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 7d1844e2888d..1a341337b272 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -1063,6 +1063,19 @@ static void hyp_poison_page(phys_addr_t phys)
 	hyp_fixmap_unmap();
 }
 
+#define KVM_HOST_INVALID_PTE_GUEST_HANDLE_MASK	GENMASK(15, 0)
+#define KVM_HOST_INVALID_PTE_GUEST_GFN_MASK	GENMASK(56, 16)
+static u64 host_stage2_encode_gfn_meta(struct pkvm_hyp_vm *vm, u64 gfn)
+{
+	pkvm_handle_t handle = vm->kvm.arch.pkvm.handle;
+
+	WARN_ON(!FIELD_FIT(KVM_HOST_INVALID_PTE_GUEST_HANDLE_MASK, handle));
+	WARN_ON(!FIELD_FIT(KVM_HOST_INVALID_PTE_GUEST_GFN_MASK, gfn));
+
+	return FIELD_PREP(KVM_HOST_INVALID_PTE_GUEST_HANDLE_MASK, handle) |
+	       FIELD_PREP(KVM_HOST_INVALID_PTE_GUEST_GFN_MASK, gfn);
+}
+
 int __pkvm_host_reclaim_page_guest(u64 gfn, struct pkvm_hyp_vm *vm)
 {
 	u64 ipa = hyp_pfn_to_phys(gfn);
@@ -1105,6 +1118,7 @@ int __pkvm_host_donate_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu)
 	struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
 	u64 phys = hyp_pfn_to_phys(pfn);
 	u64 ipa = hyp_pfn_to_phys(gfn);
+	u64 meta;
 	int ret;
 
 	host_lock_component();
@@ -1118,7 +1132,9 @@ int __pkvm_host_donate_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu)
 	if (ret)
 		goto unlock;
 
-	WARN_ON(host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_GUEST));
+	meta = host_stage2_encode_gfn_meta(vm, gfn);
+	WARN_ON(host_stage2_set_owner_metadata_locked(phys, PAGE_SIZE,
+						      PKVM_ID_GUEST, meta));
 	WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys,
 				       pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_OWNED),
 				       &vcpu->vcpu.arch.pkvm_memcache, 0));
-- 
2.52.0.351.gbe84eed79e-goog