[PATCH v7 11/45] arm64: RME: RTT tear down

Steven Price
2025-02-13T16:15:32Z

The RMM owns the stage 2 page tables for a realm, and KVM must request
that the RMM creates/destroys entries as necessary. The physical pages
to store the page tables are delegated to the realm as required, and can
be undelegated when no longer used.

Creating new RTTs is the easy part, tearing down is a little more
tricky. The result of realm_rtt_destroy() can be used to effectively
walk the tree and destroy the entries (undelegating pages that were
given to the realm).

Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Changes since v6:
* Move rme_rtt_level_mapsize() and supporting defines from kvm_rme.h
into rme.c as they are only used in that file.
Changes since v5:
* Rename some RME_xxx defines to do with page sizes as RMM_xxx - they are
a property of the RMM specification not the RME architecture.
Changes since v2:
* Moved {alloc,free}_delegated_page() and ensure_spare_page() to a
later patch when they are actually used.
* Some simplifications now rmi_xxx() functions allow NULL as an output
parameter.
* Improved comments and code layout.
---
arch/arm64/include/asm/kvm_rme.h | 7 ++
arch/arm64/kvm/mmu.c | 6 +-
arch/arm64/kvm/rme.c | 128 +++++++++++++++++++++++++++++++
3 files changed, 138 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
index 209cd99f03dd..698bb48a8ae1 100644
--- a/arch/arm64/include/asm/kvm_rme.h
+++ b/arch/arm64/include/asm/kvm_rme.h
@@ -71,5 +71,12 @@ u32 kvm_realm_ipa_limit(void);
int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
int kvm_init_realm_vm(struct kvm *kvm);
void kvm_destroy_realm(struct kvm *kvm);
+void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits);
+
+static inline bool kvm_realm_is_private_address(struct realm *realm,
+ unsigned long addr)
+{
+ return !(addr & BIT(realm->ia_bits - 1));
+}

#endif
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f8ad8f88bbb8..b4506484913d 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1070,14 +1070,15 @@ void stage2_unmap_vm(struct kvm *kvm)
void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
{
struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu);
- struct kvm_pgtable *pgt = NULL;
+ struct kvm_pgtable *pgt;

write_lock(&kvm->mmu_lock);
+ pgt = mmu->pgt;
if (kvm_is_realm(kvm) &&
(kvm_realm_state(kvm) != REALM_STATE_DEAD &&
kvm_realm_state(kvm) != REALM_STATE_NONE)) {
- /* Tearing down RTTs will be added in a later patch */
write_unlock(&kvm->mmu_lock);
+ kvm_realm_destroy_rtts(kvm, pgt->ia_bits);

/*
* The physical PGD pages are delegated to the RMM, so cannot
@@ -1087,7 +1088,6 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
*/
return;
}
- pgt = mmu->pgt;
if (pgt) {
mmu->pgd_phys = 0;
mmu->pgt = NULL;
diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
index 86a40a3c8890..f5d79efee454 100644
--- a/arch/arm64/kvm/rme.c
+++ b/arch/arm64/kvm/rme.c
@@ -17,6 +17,22 @@ static unsigned long rmm_feat_reg0;
#define RMM_PAGE_SHIFT 12
#define RMM_PAGE_SIZE BIT(RMM_PAGE_SHIFT)

+#define RMM_RTT_BLOCK_LEVEL 2
+#define RMM_RTT_MAX_LEVEL 3
+
+/* See ARM64_HW_PGTABLE_LEVEL_SHIFT() */
+#define RMM_RTT_LEVEL_SHIFT(l) \
+ ((RMM_PAGE_SHIFT - 3) * (4 - (l)) + 3)
+#define RMM_L2_BLOCK_SIZE BIT(RMM_RTT_LEVEL_SHIFT(2))
+
+static inline unsigned long rme_rtt_level_mapsize(int level)
+{
+ if (WARN_ON(level > RMM_RTT_MAX_LEVEL))
+ return RMM_PAGE_SIZE;
+
+ return (1UL << RMM_RTT_LEVEL_SHIFT(level));
+}
+
static bool rme_has_feature(unsigned long feature)
{
return !!u64_get_bits(rmm_feat_reg0, feature);
@@ -173,6 +189,118 @@ static int realm_create_rd(struct kvm *kvm)
return r;
}

+static int realm_rtt_destroy(struct realm *realm, unsigned long addr,
+ int level, phys_addr_t *rtt_granule,
+ unsigned long *next_addr)
+{
+ unsigned long out_rtt;
+ int ret;
+
+ ret = rmi_rtt_destroy(virt_to_phys(realm->rd), addr, level,
+ &out_rtt, next_addr);
+
+ *rtt_granule = out_rtt;
+
+ return ret;
+}
+
+static int realm_tear_down_rtt_level(struct realm *realm, int level,
+ unsigned long start, unsigned long end)
+{
+ ssize_t map_size;
+ unsigned long addr, next_addr;
+
+ if (WARN_ON(level > RMM_RTT_MAX_LEVEL))
+ return -EINVAL;
+
+ map_size = rme_rtt_level_mapsize(level - 1);
+
+ for (addr = start; addr < end; addr = next_addr) {
+ phys_addr_t rtt_granule;
+ int ret;
+ unsigned long align_addr = ALIGN(addr, map_size);
+
+ next_addr = ALIGN(addr + 1, map_size);
+
+ if (next_addr > end || align_addr != addr) {
+ /*
+ * The target range is smaller than what this level
+ * covers, recurse deeper.
+ */
+ ret = realm_tear_down_rtt_level(realm,
+ level + 1,
+ addr,
+ min(next_addr, end));
+ if (ret)
+ return ret;
+ continue;
+ }
+
+ ret = realm_rtt_destroy(realm, addr, level,
+ &rtt_granule, &next_addr);
+
+ switch (RMI_RETURN_STATUS(ret)) {
+ case RMI_SUCCESS:
+ free_delegated_granule(rtt_granule);
+ break;
+ case RMI_ERROR_RTT:
+ if (next_addr > addr) {
+ /* Missing RTT, skip */
+ break;
+ }
+ /*
+ * We tear down the RTT range for the full IPA
+ * space, after everything is unmapped. Also we
+ * descend down only if we cannot tear down a
+ * top level RTT. Thus RMM must be able to walk
+ * to the requested level. e.g., a block mapping
+ * exists at L1 or L2.
+ */
+ if (WARN_ON(RMI_RETURN_INDEX(ret) != level))
+ return -EBUSY;
+ if (WARN_ON(level == RMM_RTT_MAX_LEVEL))
+ return -EBUSY;
+
+ /*
+ * The table has active entries in it, recurse deeper
+ * and tear down the RTTs.
+ */
+ next_addr = ALIGN(addr + 1, map_size);
+ ret = realm_tear_down_rtt_level(realm,
+ level + 1,
+ addr,
+ next_addr);
+ if (ret)
+ return ret;
+ /*
+ * Now that the child RTTs are destroyed,
+ * retry at this level.
+ */
+ next_addr = addr;
+ break;
+ default:
+ WARN_ON(1);
+ return -ENXIO;
+ }
+ }
+
+ return 0;
+}
+
+static int realm_tear_down_rtt_range(struct realm *realm,
+ unsigned long start, unsigned long end)
+{
+ return realm_tear_down_rtt_level(realm, get_start_level(realm) + 1,
+ start, end);
+}
+
+void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits)
+{
+ struct realm *realm = &kvm->arch.realm;
+
+ WARN_ON(realm_tear_down_rtt_range(realm, 0, (1UL << ia_bits)));
+}
+
/* Protects access to rme_vmid_bitmap */
static DEFINE_SPINLOCK(rme_vmid_lock);
static unsigned long *rme_vmid_bitmap;
--
2.43.0