1 files changed, 799 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
new file mode 100644
index 000000000000..07f9dc9848ef
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -0,0 +1,799 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Google LLC
+ * Author: Quentin Perret <qperret@google.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <asm/kvm_emulate.h>
+#include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
+#include <asm/kvm_pgtable.h>
+#include <asm/kvm_pkvm.h>
+#include <asm/stage2_pgtable.h>
+
+#include <hyp/fault.h>
+
+#include <nvhe/gfp.h>
+#include <nvhe/memory.h>
+#include <nvhe/mem_protect.h>
+#include <nvhe/mm.h>
+
+#define KVM_HOST_S2_FLAGS (KVM_PGTABLE_S2_NOFWB | KVM_PGTABLE_S2_IDMAP)
+
+extern unsigned long hyp_nr_cpus;
+struct host_kvm host_kvm;
+
+static struct hyp_pool host_s2_pool;
+
+const u8 pkvm_hyp_id = 1;
+
+static void host_lock_component(void)
+{
+	hyp_spin_lock(&host_kvm.lock);
+}
+
+static void host_unlock_component(void)
+{
+	hyp_spin_unlock(&host_kvm.lock);
+}
+
+static void hyp_lock_component(void)
+{
+	hyp_spin_lock(&pkvm_pgd_lock);
+}
+
+static void hyp_unlock_component(void)
+{
+	hyp_spin_unlock(&pkvm_pgd_lock);
+}
+
+static void *host_s2_zalloc_pages_exact(size_t size)
+{
+	void *addr = hyp_alloc_pages(&host_s2_pool, get_order(size));
+
+	hyp_split_page(hyp_virt_to_page(addr));
+
+	/*
+	 * The size of concatenated PGDs is always a power of two of PAGE_SIZE,
+	 * so there should be no need to free any of the tail pages to make the
+	 * allocation exact.
+	 */
+	WARN_ON(size != (PAGE_SIZE << get_order(size)));
+
+	return addr;
+}
+
+static void *host_s2_zalloc_page(void *pool)
+{
+	return hyp_alloc_pages(pool, 0);
+}
+
+static void host_s2_get_page(void *addr)
+{
+	hyp_get_page(&host_s2_pool, addr);
+}
+
+static void host_s2_put_page(void *addr)
+{
+	hyp_put_page(&host_s2_pool, addr);
+}
+
+static int prepare_s2_pool(void *pgt_pool_base)
+{
+	unsigned long nr_pages, pfn;
+	int ret;
+
+	pfn = hyp_virt_to_pfn(pgt_pool_base);
+	nr_pages = host_s2_pgtable_pages();
+	ret = hyp_pool_init(&host_s2_pool, pfn, nr_pages, 0);
+	if (ret)
+		return ret;
+
+	host_kvm.mm_ops = (struct kvm_pgtable_mm_ops) {
+		.zalloc_pages_exact = host_s2_zalloc_pages_exact,
+		.zalloc_page = host_s2_zalloc_page,
+		.phys_to_virt = hyp_phys_to_virt,
+		.virt_to_phys = hyp_virt_to_phys,
+		.page_count = hyp_page_count,
+		.get_page = host_s2_get_page,
+		.put_page = host_s2_put_page,
+	};
+
+	return 0;
+}
+
+static void prepare_host_vtcr(void)
+{
+	u32 parange, phys_shift;
+
+	/* The host stage 2 is id-mapped, so use parange for T0SZ */
+	parange = kvm_get_parange(id_aa64mmfr0_el1_sys_val);
+	phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
+
+	host_kvm.arch.vtcr = kvm_get_vtcr(id_aa64mmfr0_el1_sys_val,
+					  id_aa64mmfr1_el1_sys_val, phys_shift);
+}
+
+static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot);
+
+int kvm_host_prepare_stage2(void *pgt_pool_base)
+{
+	struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu;
+	int ret;
+
+	prepare_host_vtcr();
+	hyp_spin_lock_init(&host_kvm.lock);
+	mmu->arch = &host_kvm.arch;
+
+	ret = prepare_s2_pool(pgt_pool_base);
+	if (ret)
+		return ret;
+
+	ret = __kvm_pgtable_stage2_init(&host_kvm.pgt, mmu,
+					&host_kvm.mm_ops, KVM_HOST_S2_FLAGS,
+					host_stage2_force_pte_cb);
+	if (ret)
+		return ret;
+
+	mmu->pgd_phys = __hyp_pa(host_kvm.pgt.pgd);
+	mmu->pgt = &host_kvm.pgt;
+	atomic64_set(&mmu->vmid.id, 0);
+
+	return 0;
+}
+
+int __pkvm_prot_finalize(void)
+{
+	struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu;
+	struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
+
+	if (params->hcr_el2 & HCR_VM)
+		return -EPERM;
+
+	params->vttbr = kvm_get_vttbr(mmu);
+	params->vtcr = host_kvm.arch.vtcr;
+	params->hcr_el2 |= HCR_VM;
+	kvm_flush_dcache_to_poc(params, sizeof(*params));
+
+	write_sysreg(params->hcr_el2, hcr_el2);
+	__load_stage2(&host_kvm.arch.mmu, &host_kvm.arch);
+
+	/*
+	 * Make sure to have an ISB before the TLB maintenance below but only
+	 * when __load_stage2() doesn't include one already.
+	 */
+	asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
+
+	/* Invalidate stale HCR bits that may be cached in TLBs */
+	__tlbi(vmalls12e1);
+	dsb(nsh);
+	isb();
+
+	return 0;
+}
+
+static int host_stage2_unmap_dev_all(void)
+{
+	struct kvm_pgtable *pgt = &host_kvm.pgt;
+	struct memblock_region *reg;
+	u64 addr = 0;
+	int i, ret;
+
+	/* Unmap all non-memory regions to recycle the pages */
+	for (i = 0; i < hyp_memblock_nr; i++, addr = reg->base + reg->size) {
+		reg = &hyp_memory[i];
+		ret = kvm_pgtable_stage2_unmap(pgt, addr, reg->base - addr);
+		if (ret)
+			return ret;
+	}
+	return kvm_pgtable_stage2_unmap(pgt, addr, BIT(pgt->ia_bits) - addr);
+}
+
+struct kvm_mem_range {
+	u64 start;
+	u64 end;
+};
+
+static bool find_mem_range(phys_addr_t addr, struct kvm_mem_range *range)
+{
+	int cur, left = 0, right = hyp_memblock_nr;
+	struct memblock_region *reg;
+	phys_addr_t end;
+
+	range->start = 0;
+	range->end = ULONG_MAX;
+
+	/* The list of memblock regions is sorted, binary search it */
+	while (left < right) {
+		cur = (left + right) >> 1;
+		reg = &hyp_memory[cur];
+		end = reg->base + reg->size;
+		if (addr < reg->base) {
+			right = cur;
+			range->end = reg->base;
+		} else if (addr >= end) {
+			left = cur + 1;
+			range->start = end;
+		} else {
+			range->start = reg->base;
+			range->end = end;
+			return true;
+		}
+	}
+
+	return false;
+}
+
+bool addr_is_memory(phys_addr_t phys)
+{
+	struct kvm_mem_range range;
+
+	return find_mem_range(phys, &range);
+}
+
+static bool is_in_mem_range(u64 addr, struct kvm_mem_range *range)
+{
+	return range->start <= addr && addr < range->end;
+}
+
+static bool range_is_memory(u64 start, u64 end)
+{
+	struct kvm_mem_range r;
+
+	if (!find_mem_range(start, &r))
+		return false;
+
+	return is_in_mem_range(end - 1, &r);
+}
+
+static inline int __host_stage2_idmap(u64 start, u64 end,
+				      enum kvm_pgtable_prot prot)
+{
+	return kvm_pgtable_stage2_map(&host_kvm.pgt, start, end - start, start,
+				      prot, &host_s2_pool);
+}
+
+/*
+ * The pool has been provided with enough pages to cover all of memory with
+ * page granularity, but it is difficult to know how much of the MMIO range
+ * we will need to cover upfront, so we may need to 'recycle' the pages if we
+ * run out.
+ */
+#define host_stage2_try(fn, ...)					\
+	({								\
+		int __ret;						\
+		hyp_assert_lock_held(&host_kvm.lock);			\
+		__ret = fn(__VA_ARGS__);				\
+		if (__ret == -ENOMEM) {					\
+			__ret = host_stage2_unmap_dev_all();		\
+			if (!__ret)					\
+				__ret = fn(__VA_ARGS__);		\
+		}							\
+		__ret;							\
+	 })
+
+static inline bool range_included(struct kvm_mem_range *child,
+				  struct kvm_mem_range *parent)
+{
+	return parent->start <= child->start && child->end <= parent->end;
+}
+
+static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range)
+{
+	struct kvm_mem_range cur;
+	kvm_pte_t pte;
+	u32 level;
+	int ret;
+
+	hyp_assert_lock_held(&host_kvm.lock);
+	ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level);
+	if (ret)
+		return ret;
+
+	if (kvm_pte_valid(pte))
+		return -EAGAIN;
+
+	if (pte)
+		return -EPERM;
+
+	do {
+		u64 granule = kvm_granule_size(level);
+		cur.start = ALIGN_DOWN(addr, granule);
+		cur.end = cur.start + granule;
+		level++;
+	} while ((level < KVM_PGTABLE_MAX_LEVELS) &&
+			!(kvm_level_supports_block_mapping(level) &&
+			  range_included(&cur, range)));
+
+	*range = cur;
+
+	return 0;
+}
+
+int host_stage2_idmap_locked(phys_addr_t addr, u64 size,
+			     enum kvm_pgtable_prot prot)
+{
+	return host_stage2_try(__host_stage2_idmap, addr, addr + size, prot);
+}
+
+int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id)
+{
+	return host_stage2_try(kvm_pgtable_stage2_set_owner, &host_kvm.pgt,
+			       addr, size, &host_s2_pool, owner_id);
+}
+
+static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot)
+{
+	/*
+	 * Block mappings must be used with care in the host stage-2 as a
+	 * kvm_pgtable_stage2_map() operation targeting a page in the range of
+	 * an existing block will delete the block under the assumption that
+	 * mappings in the rest of the block range can always be rebuilt lazily.
+	 * That assumption is correct for the host stage-2 with RWX mappings
+	 * targeting memory or RW mappings targeting MMIO ranges (see
+	 * host_stage2_idmap() below which implements some of the host memory
+	 * abort logic). However, this is not safe for any other mappings where
+	 * the host stage-2 page-table is in fact the only place where this
+	 * state is stored. In all those cases, it is safer to use page-level
+	 * mappings, hence avoiding to lose the state because of side-effects in
+	 * kvm_pgtable_stage2_map().
+	 */
+	if (range_is_memory(addr, end))
+		return prot != PKVM_HOST_MEM_PROT;
+	else
+		return prot != PKVM_HOST_MMIO_PROT;
+}
+
+static int host_stage2_idmap(u64 addr)
+{
+	struct kvm_mem_range range;
+	bool is_memory = find_mem_range(addr, &range);
+	enum kvm_pgtable_prot prot;
+	int ret;
+
+	prot = is_memory ? PKVM_HOST_MEM_PROT : PKVM_HOST_MMIO_PROT;
+
+	host_lock_component();
+	ret = host_stage2_adjust_range(addr, &range);
+	if (ret)
+		goto unlock;
+
+	ret = host_stage2_idmap_locked(range.start, range.end - range.start, prot);
+unlock:
+	host_unlock_component();
+
+	return ret;
+}
+
+void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
+{
+	struct kvm_vcpu_fault_info fault;
+	u64 esr, addr;
+	int ret = 0;
+
+	esr = read_sysreg_el2(SYS_ESR);
+	BUG_ON(!__get_fault_info(esr, &fault));
+
+	addr = (fault.hpfar_el2 & HPFAR_MASK) << 8;
+	ret = host_stage2_idmap(addr);
+	BUG_ON(ret && ret != -EAGAIN);
+}
+
+/* This corresponds to locking order */
+enum pkvm_component_id {
+	PKVM_ID_HOST,
+	PKVM_ID_HYP,
+};
+
+struct pkvm_mem_transition {
+	u64				nr_pages;
+
+	struct {
+		enum pkvm_component_id	id;
+		/* Address in the initiator's address space */
+		u64			addr;
+
+		union {
+			struct {
+				/* Address in the completer's address space */
+				u64	completer_addr;
+			} host;
+		};
+	} initiator;
+
+	struct {
+		enum pkvm_component_id	id;
+	} completer;
+};
+
+struct pkvm_mem_share {
+	const struct pkvm_mem_transition	tx;
+	const enum kvm_pgtable_prot		completer_prot;
+};
+
+struct check_walk_data {
+	enum pkvm_page_state	desired;
+	enum pkvm_page_state	(*get_page_state)(kvm_pte_t pte);
+};
+
+static int __check_page_state_visitor(u64 addr, u64 end, u32 level,
+				      kvm_pte_t *ptep,
+				      enum kvm_pgtable_walk_flags flag,
+				      void * const arg)
+{
+	struct check_walk_data *d = arg;
+	kvm_pte_t pte = *ptep;
+
+	if (kvm_pte_valid(pte) && !addr_is_memory(kvm_pte_to_phys(pte)))
+		return -EINVAL;
+
+	return d->get_page_state(pte) == d->desired ? 0 : -EPERM;
+}
+
+static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size,
+				  struct check_walk_data *data)
+{
+	struct kvm_pgtable_walker walker = {
+		.cb	= __check_page_state_visitor,
+		.arg	= data,
+		.flags	= KVM_PGTABLE_WALK_LEAF,
+	};
+
+	return kvm_pgtable_walk(pgt, addr, size, &walker);
+}
+
+static enum pkvm_page_state host_get_page_state(kvm_pte_t pte)
+{
+	if (!kvm_pte_valid(pte) && pte)
+		return PKVM_NOPAGE;
+
+	return pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte));
+}
+
+static int __host_check_page_state_range(u64 addr, u64 size,
+					 enum pkvm_page_state state)
+{
+	struct check_walk_data d = {
+		.desired	= state,
+		.get_page_state	= host_get_page_state,
+	};
+
+	hyp_assert_lock_held(&host_kvm.lock);
+	return check_page_state_range(&host_kvm.pgt, addr, size, &d);
+}
+
+static int __host_set_page_state_range(u64 addr, u64 size,
+				       enum pkvm_page_state state)
+{
+	enum kvm_pgtable_prot prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, state);
+
+	return host_stage2_idmap_locked(addr, size, prot);
+}
+
+static int host_request_owned_transition(u64 *completer_addr,
+					 const struct pkvm_mem_transition *tx)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+	u64 addr = tx->initiator.addr;
+
+	*completer_addr = tx->initiator.host.completer_addr;
+	return __host_check_page_state_range(addr, size, PKVM_PAGE_OWNED);
+}
+
+static int host_request_unshare(u64 *completer_addr,
+				const struct pkvm_mem_transition *tx)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+	u64 addr = tx->initiator.addr;
+
+	*completer_addr = tx->initiator.host.completer_addr;
+	return __host_check_page_state_range(addr, size, PKVM_PAGE_SHARED_OWNED);
+}
+
+static int host_initiate_share(u64 *completer_addr,
+			       const struct pkvm_mem_transition *tx)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+	u64 addr = tx->initiator.addr;
+
+	*completer_addr = tx->initiator.host.completer_addr;
+	return __host_set_page_state_range(addr, size, PKVM_PAGE_SHARED_OWNED);
+}
+
+static int host_initiate_unshare(u64 *completer_addr,
+				 const struct pkvm_mem_transition *tx)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+	u64 addr = tx->initiator.addr;
+
+	*completer_addr = tx->initiator.host.completer_addr;
+	return __host_set_page_state_range(addr, size, PKVM_PAGE_OWNED);
+}
+
+static enum pkvm_page_state hyp_get_page_state(kvm_pte_t pte)
+{
+	if (!kvm_pte_valid(pte))
+		return PKVM_NOPAGE;
+
+	return pkvm_getstate(kvm_pgtable_hyp_pte_prot(pte));
+}
+
+static int __hyp_check_page_state_range(u64 addr, u64 size,
+					enum pkvm_page_state state)
+{
+	struct check_walk_data d = {
+		.desired	= state,
+		.get_page_state	= hyp_get_page_state,
+	};
+
+	hyp_assert_lock_held(&pkvm_pgd_lock);
+	return check_page_state_range(&pkvm_pgtable, addr, size, &d);
+}
+
+static bool __hyp_ack_skip_pgtable_check(const struct pkvm_mem_transition *tx)
+{
+	return !(IS_ENABLED(CONFIG_NVHE_EL2_DEBUG) ||
+		 tx->initiator.id != PKVM_ID_HOST);
+}
+
+static int hyp_ack_share(u64 addr, const struct pkvm_mem_transition *tx,
+			 enum kvm_pgtable_prot perms)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+
+	if (perms != PAGE_HYP)
+		return -EPERM;
+
+	if (__hyp_ack_skip_pgtable_check(tx))
+		return 0;
+
+	return __hyp_check_page_state_range(addr, size, PKVM_NOPAGE);
+}
+
+static int hyp_ack_unshare(u64 addr, const struct pkvm_mem_transition *tx)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+
+	if (__hyp_ack_skip_pgtable_check(tx))
+		return 0;
+
+	return __hyp_check_page_state_range(addr, size,
+					    PKVM_PAGE_SHARED_BORROWED);
+}
+
+static int hyp_complete_share(u64 addr, const struct pkvm_mem_transition *tx,
+			      enum kvm_pgtable_prot perms)
+{
+	void *start = (void *)addr, *end = start + (tx->nr_pages * PAGE_SIZE);
+	enum kvm_pgtable_prot prot;
+
+	prot = pkvm_mkstate(perms, PKVM_PAGE_SHARED_BORROWED);
+	return pkvm_create_mappings_locked(start, end, prot);
+}
+
+static int hyp_complete_unshare(u64 addr, const struct pkvm_mem_transition *tx)
+{
+	u64 size = tx->nr_pages * PAGE_SIZE;
+	int ret = kvm_pgtable_hyp_unmap(&pkvm_pgtable, addr, size);
+
+	return (ret != size) ? -EFAULT : 0;
+}
+
+static int check_share(struct pkvm_mem_share *share)
+{
+	const struct pkvm_mem_transition *tx = &share->tx;
+	u64 completer_addr;
+	int ret;
+
+	switch (tx->initiator.id) {
+	case PKVM_ID_HOST:
+		ret = host_request_owned_transition(&completer_addr, tx);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	switch (tx->completer.id) {
+	case PKVM_ID_HYP:
+		ret = hyp_ack_share(completer_addr, tx, share->completer_prot);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int __do_share(struct pkvm_mem_share *share)
+{
+	const struct pkvm_mem_transition *tx = &share->tx;
+	u64 completer_addr;
+	int ret;
+
+	switch (tx->initiator.id) {
+	case PKVM_ID_HOST:
+		ret = host_initiate_share(&completer_addr, tx);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	switch (tx->completer.id) {
+	case PKVM_ID_HYP:
+		ret = hyp_complete_share(completer_addr, tx, share->completer_prot);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+/*
+ * do_share():
+ *
+ * The page owner grants access to another component with a given set
+ * of permissions.
+ *
+ * Initiator: OWNED	=> SHARED_OWNED
+ * Completer: NOPAGE	=> SHARED_BORROWED
+ */
+static int do_share(struct pkvm_mem_share *share)
+{
+	int ret;
+
+	ret = check_share(share);
+	if (ret)
+		return ret;
+
+	return WARN_ON(__do_share(share));
+}
+
+static int check_unshare(struct pkvm_mem_share *share)
+{
+	const struct pkvm_mem_transition *tx = &share->tx;
+	u64 completer_addr;
+	int ret;
+
+	switch (tx->initiator.id) {
+	case PKVM_ID_HOST:
+		ret = host_request_unshare(&completer_addr, tx);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	switch (tx->completer.id) {
+	case PKVM_ID_HYP:
+		ret = hyp_ack_unshare(completer_addr, tx);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int __do_unshare(struct pkvm_mem_share *share)
+{
+	const struct pkvm_mem_transition *tx = &share->tx;
+	u64 completer_addr;
+	int ret;
+
+	switch (tx->initiator.id) {
+	case PKVM_ID_HOST:
+		ret = host_initiate_unshare(&completer_addr, tx);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	switch (tx->completer.id) {
+	case PKVM_ID_HYP:
+		ret = hyp_complete_unshare(completer_addr, tx);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+/*
+ * do_unshare():
+ *
+ * The page owner revokes access from another component for a range of
+ * pages which were previously shared using do_share().
+ *
+ * Initiator: SHARED_OWNED	=> OWNED
+ * Completer: SHARED_BORROWED	=> NOPAGE
+ */
+static int do_unshare(struct pkvm_mem_share *share)
+{
+	int ret;
+
+	ret = check_unshare(share);
+	if (ret)
+		return ret;
+
+	return WARN_ON(__do_unshare(share));
+}
+
+int __pkvm_host_share_hyp(u64 pfn)
+{
+	int ret;
+	u64 host_addr = hyp_pfn_to_phys(pfn);
+	u64 hyp_addr = (u64)__hyp_va(host_addr);
+	struct pkvm_mem_share share = {
+		.tx	= {
+			.nr_pages	= 1,
+			.initiator	= {
+				.id	= PKVM_ID_HOST,
+				.addr	= host_addr,
+				.host	= {
+					.completer_addr = hyp_addr,
+				},
+			},
+			.completer	= {
+				.id	= PKVM_ID_HYP,
+			},
+		},
+		.completer_prot	= PAGE_HYP,
+	};
+
+	host_lock_component();
+	hyp_lock_component();
+
+	ret = do_share(&share);
+
+	hyp_unlock_component();
+	host_unlock_component();
+
+	return ret;
+}
+
+int __pkvm_host_unshare_hyp(u64 pfn)
+{
+	int ret;
+	u64 host_addr = hyp_pfn_to_phys(pfn);
+	u64 hyp_addr = (u64)__hyp_va(host_addr);
+	struct pkvm_mem_share share = {
+		.tx	= {
+			.nr_pages	= 1,
+			.initiator	= {
+				.id	= PKVM_ID_HOST,
+				.addr	= host_addr,
+				.host	= {
+					.completer_addr = hyp_addr,
+				},
+			},
+			.completer	= {
+				.id	= PKVM_ID_HYP,
+			},
+		},
+		.completer_prot	= PAGE_HYP,
+	};
+
+	host_lock_component();
+	hyp_lock_component();
+
+	ret = do_unshare(&share);
+
+	hyp_unlock_component();
+	host_unlock_component();
+
+	return ret;
+}