[PATCH v5 10/10] arm64: realm: Expose the CCA shared granule size through mem_encrypt ops

[Aneesh Kumar K.V (Arm)]

CCA guests must align shared/private memory transitions to the size
reported by the host for IPA state changes. This size can be larger than
PAGE_SIZE, so allowing a guest to convert only a PAGE_SIZE-sized subrange
can leave the remaining part of that host-sized range in the wrong state.

Cache the RHI-reported IPA sate change alignment during Realm
initialization and expose it through a new arm64 mem_encrypt callback. Use
PAGE_SIZE as the default shared granule size when no backend callback is
registered.

Validate both the address and byte size passed to set_memory_encrypted()
and set_memory_decrypted() against mem_cc_shared_granule_size() before
calling into the backend. This prevents callers from converting only part
of a host-managed page.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar at kernel.org>
---
 arch/arm64/include/asm/mem_encrypt.h |  4 ++++
 arch/arm64/kernel/rsi.c              | 13 ++++++++++-
 arch/arm64/mm/mem_encrypt.c          | 32 ++++++++++++++++++++++++----
 3 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/mem_encrypt.h b/arch/arm64/include/asm/mem_encrypt.h
index f6325f30e844..5018581fed87 100644
--- a/arch/arm64/include/asm/mem_encrypt.h
+++ b/arch/arm64/include/asm/mem_encrypt.h
@@ -9,6 +9,7 @@ struct device;
 struct arm64_mem_crypt_ops {
 	int (*encrypt)(unsigned long addr, int numpages);
 	int (*decrypt)(unsigned long addr, int numpages);
+	size_t (*cc_shared_granule_size)(void);
 };
 
 int arm64_mem_crypt_ops_register(const struct arm64_mem_crypt_ops *ops);
@@ -17,6 +18,9 @@ int set_memory_encrypted(unsigned long addr, int numpages);
 int set_memory_decrypted(unsigned long addr, int numpages);
 int __set_memory_enc_dec(unsigned long addr, int numpages, bool encrypt);
 
+#define mem_cc_shared_granule_size mem_cc_shared_granule_size
+size_t mem_cc_shared_granule_size(void);
+
 static inline bool force_dma_unencrypted(struct device *dev)
 {
 	return is_realm_world();
diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index f52f240bb44c..54fb929067c9 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -20,6 +20,7 @@
 
 static struct realm_config config;
 static struct kobject *cca_kobj;
+static unsigned long ipa_state_change_granule_size;
 
 unsigned long prot_ns_shared;
 EXPORT_SYMBOL(prot_ns_shared);
@@ -168,9 +169,17 @@ static int realm_set_memory_decrypted(unsigned long addr, int numpages)
 	return ret;
 }
 
+static size_t realm_cc_shared_granule_size(void)
+{
+	if (is_realm_world())
+		return ipa_state_change_granule_size;
+	return PAGE_SIZE;
+}
+
 static const struct arm64_mem_crypt_ops realm_crypt_ops = {
 	.encrypt = realm_set_memory_encrypted,
 	.decrypt = realm_set_memory_decrypted,
+	.cc_shared_granule_size = realm_cc_shared_granule_size,
 };
 
 static int realm_register_memory_enc_ops(void)
@@ -180,7 +189,7 @@ static int realm_register_memory_enc_ops(void)
 
 /* we need an aligned struct for rsi_host_call. slab is not yet ready */
 static struct rsi_host_call hostconf_call __initdata;
-static unsigned long __maybe_unused __init get_ipa_state_change_alignment(void)
+static unsigned long __init get_ipa_state_change_alignment(void)
 {
 	long ret;
 	unsigned long shared_granule_size;
@@ -230,6 +239,8 @@ void __init arm64_rsi_init(void)
 		return;
 	if (WARN_ON(rsi_get_realm_config(lm_alias(&config))))
 		return;
+
+	ipa_state_change_granule_size = get_ipa_state_change_alignment();
 	prot_ns_shared = __phys_to_pte_val(BIT(config.ipa_bits - 1));
 
 	if (arm64_ioremap_prot_hook_register(realm_ioremap_hook))
diff --git a/arch/arm64/mm/mem_encrypt.c b/arch/arm64/mm/mem_encrypt.c
index ee3c0ab04384..69783c6a3c08 100644
--- a/arch/arm64/mm/mem_encrypt.c
+++ b/arch/arm64/mm/mem_encrypt.c
@@ -17,8 +17,7 @@
 #include <linux/compiler.h>
 #include <linux/err.h>
 #include <linux/mm.h>
-
-#include <asm/mem_encrypt.h>
+#include <linux/mem_encrypt.h>
 
 static const struct arm64_mem_crypt_ops *crypt_ops;
 
@@ -33,18 +32,43 @@ int arm64_mem_crypt_ops_register(const struct arm64_mem_crypt_ops *ops)
 
 int set_memory_encrypted(unsigned long addr, int numpages)
 {
-	if (likely(!crypt_ops) || WARN_ON(!PAGE_ALIGNED(addr)))
+	unsigned long size = (unsigned long)numpages << PAGE_SHIFT;
+
+	if (likely(!crypt_ops))
 		return 0;
 
+	if (WARN_ON(!IS_ALIGNED(addr, mem_cc_shared_granule_size())))
+		return -EINVAL;
+
+	if (WARN_ON(!IS_ALIGNED(size, mem_cc_shared_granule_size())))
+		return -EINVAL;
+
 	return crypt_ops->encrypt(addr, numpages);
 }
 EXPORT_SYMBOL_GPL(set_memory_encrypted);
 
 int set_memory_decrypted(unsigned long addr, int numpages)
 {
-	if (likely(!crypt_ops) || WARN_ON(!PAGE_ALIGNED(addr)))
+	unsigned long size = (unsigned long)numpages << PAGE_SHIFT;
+
+	if (likely(!crypt_ops))
 		return 0;
 
+	if (WARN_ON(!IS_ALIGNED(addr, mem_cc_shared_granule_size())))
+		return -EINVAL;
+
+	if (WARN_ON(!IS_ALIGNED(size, mem_cc_shared_granule_size())))
+		return -EINVAL;
+
 	return crypt_ops->decrypt(addr, numpages);
 }
 EXPORT_SYMBOL_GPL(set_memory_decrypted);
+
+size_t mem_cc_shared_granule_size(void)
+{
+	if (likely(!crypt_ops) || !crypt_ops->cc_shared_granule_size)
+		return PAGE_SIZE;
+
+	return crypt_ops->cc_shared_granule_size();
+}
+EXPORT_SYMBOL_GPL(mem_cc_shared_granule_size);
-- 
2.43.0