[PATCH v4 21/38] KVM: arm64: Generalise kvm_pgtable_stage2_set_owner()

Will Deacon
2026-03-27T14:02:00Z

kvm_pgtable_stage2_set_owner() can be generalised into a way to store
up to 59 bits in the page tables alongside a 4-bit 'type' identifier
specific to the format of the 59-bit payload.

Introduce kvm_pgtable_stage2_annotate() and move the existing invalid
ptes (for locked ptes and donated pages) over to the new scheme.

Tested-by: Fuad Tabba <tabba@google.com>
Tested-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/kvm_pgtable.h | 39 +++++++++++++++++++--------
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 16 +++++++++--
arch/arm64/kvm/hyp/pgtable.c | 33 ++++++++++++++---------
3 files changed, 62 insertions(+), 26 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 50caca311ef5..e36c2908bdb2 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -100,13 +100,25 @@ typedef u64 kvm_pte_t;
KVM_PTE_LEAF_ATTR_HI_S2_XN)

#define KVM_INVALID_PTE_OWNER_MASK GENMASK(9, 2)
-#define KVM_MAX_OWNER_ID 2

-/*
- * Used to indicate a pte for which a 'break-before-make' sequence is in
- * progress.
- */
-#define KVM_INVALID_PTE_LOCKED BIT(10)
+/* pKVM invalid pte encodings */
+#define KVM_INVALID_PTE_TYPE_MASK GENMASK(63, 60)
+#define KVM_INVALID_PTE_ANNOT_MASK ~(KVM_PTE_VALID | \
+ KVM_INVALID_PTE_TYPE_MASK)
+
+enum kvm_invalid_pte_type {
+ /*
+ * Used to indicate a pte for which a 'break-before-make'
+ * sequence is in progress.
+ */
+ KVM_INVALID_PTE_TYPE_LOCKED = 1,
+
+ /*
+ * pKVM has unmapped the page from the host due to a change of
+ * ownership.
+ */
+ KVM_HOST_INVALID_PTE_TYPE_DONATION,
+};

static inline bool kvm_pte_valid(kvm_pte_t pte)
{
@@ -658,14 +670,18 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
void *mc, enum kvm_pgtable_walk_flags flags);

/**
- * kvm_pgtable_stage2_set_owner() - Unmap and annotate pages in the IPA space to
- * track ownership.
+ * kvm_pgtable_stage2_annotate() - Unmap and annotate pages in the IPA space
+ * to track ownership (and more).
* @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
* @addr: Base intermediate physical address to annotate.
* @size: Size of the annotated range.
* @mc: Cache of pre-allocated and zeroed memory from which to allocate
* page-table pages.
- * @owner_id: Unique identifier for the owner of the page.
+ * @type: The type of the annotation, determining its meaning and format.
+ * @annotation: A 59-bit value that will be stored in the page tables.
+ * @annotation[0] and @annotation[63:60] must be 0.
+ * @annotation[59:1] is stored in the page tables, along
+ * with @type.
*
* By default, all page-tables are owned by identifier 0. This function can be
* used to mark portions of the IPA space as owned by other entities. When a
@@ -674,8 +690,9 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
*
* Return: 0 on success, negative error code on failure.
*/
-int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size,
- void *mc, u8 owner_id);
+int kvm_pgtable_stage2_annotate(struct kvm_pgtable *pgt, u64 addr, u64 size,
+ void *mc, enum kvm_invalid_pte_type type,
+ kvm_pte_t annotation);

/**
* kvm_pgtable_stage2_unmap() - Remove a mapping from a guest stage-2 page-table.
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index bf5102594fc8..aea6ec981801 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -549,10 +549,19 @@ static void __host_update_page_state(phys_addr_t addr, u64 size, enum pkvm_page_
set_host_state(page, state);
}

+static kvm_pte_t kvm_init_invalid_leaf_owner(u8 owner_id)
+{
+ return FIELD_PREP(KVM_INVALID_PTE_OWNER_MASK, owner_id);
+}
+
int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id)
{
+ kvm_pte_t annotation;
int ret = -EINVAL;

+ if (!FIELD_FIT(KVM_INVALID_PTE_OWNER_MASK, owner_id))
+ return -EINVAL;
+
if (!range_is_memory(addr, addr + size))
return -EPERM;

@@ -564,8 +573,11 @@ int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id)
break;
case PKVM_ID_GUEST:
case PKVM_ID_HYP:
- ret = host_stage2_try(kvm_pgtable_stage2_set_owner, &host_mmu.pgt,
- addr, size, &host_s2_pool, owner_id);
+ annotation = kvm_init_invalid_leaf_owner(owner_id);
+ ret = host_stage2_try(kvm_pgtable_stage2_annotate, &host_mmu.pgt,
+ addr, size, &host_s2_pool,
+ KVM_HOST_INVALID_PTE_TYPE_DONATION,
+ annotation);
if (!ret)
__host_update_page_state(addr, size, PKVM_NOPAGE);
break;
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 9b480f947da2..84c7a1df845d 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -114,11 +114,6 @@ static kvm_pte_t kvm_init_valid_leaf_pte(u64 pa, kvm_pte_t attr, s8 level)
return pte;
}

-static kvm_pte_t kvm_init_invalid_leaf_owner(u8 owner_id)
-{
- return FIELD_PREP(KVM_INVALID_PTE_OWNER_MASK, owner_id);
-}
-
static int kvm_pgtable_visitor_cb(struct kvm_pgtable_walk_data *data,
const struct kvm_pgtable_visit_ctx *ctx,
enum kvm_pgtable_walk_flags visit)
@@ -581,7 +576,7 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
struct stage2_map_data {
const u64 phys;
kvm_pte_t attr;
- u8 owner_id;
+ kvm_pte_t pte_annot;

kvm_pte_t *anchor;
kvm_pte_t *childp;
@@ -798,7 +793,11 @@ static bool stage2_pte_is_counted(kvm_pte_t pte)

static bool stage2_pte_is_locked(kvm_pte_t pte)
{
- return !kvm_pte_valid(pte) && (pte & KVM_INVALID_PTE_LOCKED);
+ if (kvm_pte_valid(pte))
+ return false;
+
+ return FIELD_GET(KVM_INVALID_PTE_TYPE_MASK, pte) ==
+ KVM_INVALID_PTE_TYPE_LOCKED;
}

static bool stage2_try_set_pte(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t new)
@@ -829,6 +828,7 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
struct kvm_s2_mmu *mmu)
{
struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops;
+ kvm_pte_t locked_pte;

if (stage2_pte_is_locked(ctx->old)) {
/*
@@ -839,7 +839,9 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
return false;
}

- if (!stage2_try_set_pte(ctx, KVM_INVALID_PTE_LOCKED))
+ locked_pte = FIELD_PREP(KVM_INVALID_PTE_TYPE_MASK,
+ KVM_INVALID_PTE_TYPE_LOCKED);
+ if (!stage2_try_set_pte(ctx, locked_pte))
return false;

if (!kvm_pgtable_walk_skip_bbm_tlbi(ctx)) {
@@ -964,7 +966,7 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
if (!data->annotation)
new = kvm_init_valid_leaf_pte(phys, data->attr, ctx->level);
else
- new = kvm_init_invalid_leaf_owner(data->owner_id);
+ new = data->pte_annot;

/*
* Skip updating the PTE if we are trying to recreate the exact
@@ -1118,16 +1120,18 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
return ret;
}

-int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size,
- void *mc, u8 owner_id)
+int kvm_pgtable_stage2_annotate(struct kvm_pgtable *pgt, u64 addr, u64 size,
+ void *mc, enum kvm_invalid_pte_type type,
+ kvm_pte_t pte_annot)
{
int ret;
struct stage2_map_data map_data = {
.mmu = pgt->mmu,
.memcache = mc,
- .owner_id = owner_id,
.force_pte = true,
.annotation = true,
+ .pte_annot = pte_annot |
+ FIELD_PREP(KVM_INVALID_PTE_TYPE_MASK, type),
};
struct kvm_pgtable_walker walker = {
.cb = stage2_map_walker,
@@ -1136,7 +1140,10 @@ int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size,
.arg = &map_data,
};

- if (owner_id > KVM_MAX_OWNER_ID)
+ if (pte_annot & ~KVM_INVALID_PTE_ANNOT_MASK)
+ return -EINVAL;
+
+ if (!type || type == KVM_INVALID_PTE_TYPE_LOCKED)
return -EINVAL;

ret = kvm_pgtable_walk(pgt, addr, size, &walker);
--
2.53.0.1018.g2bb0e51243-goog