[RFC PATCH v7 03/13] 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 IPA state
change alignment reported by the host. This alignment can be larger than
PAGE_SIZE, so transitioning only a PAGE_SIZE-sized subrange may leave
part of the host-managed granule in the wrong state.

Cache the RHI-reported alignment during Realm initialization and expose
it through the arm64 memory encryption operations. Implement
arch_cc_shared_granule_size() so the common CoCo shared-memory allocator
uses the same constraint. Use PAGE_SIZE when no suitable backend is
registered.

The common cc_make_shared() and cc_make_private() wrappers validate both
the base and size against the architecture's shared granule size. Remove
the PAGE_SIZE-only address checks from the lower-level arm64 transition
hooks so that range validation remains in the common wrappers.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@xxxxxxxxxx>
---
 arch/arm64/include/asm/mem_encrypt.h |  1 +
 arch/arm64/mm/mem_encrypt.c          | 13 +++++++++++--
 drivers/firmware/arm_rmm/rsi.c       | 13 ++++++++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/mem_encrypt.h b/arch/arm64/include/asm/mem_encrypt.h
index ef8b8463e52b..32064338c9b0 100644
--- a/arch/arm64/include/asm/mem_encrypt.h
+++ b/arch/arm64/include/asm/mem_encrypt.h
@@ -10,6 +10,7 @@ struct device;
 struct arm64_mem_crypt_ops {
 	int (*encrypt)(unsigned long addr, int numpages);
 	int (*decrypt)(unsigned long addr, int numpages);
+	size_t (*shared_granule_size)(void);
 };
 
 int arm64_mem_crypt_ops_register(const struct arm64_mem_crypt_ops *ops);
diff --git a/arch/arm64/mm/mem_encrypt.c b/arch/arm64/mm/mem_encrypt.c
index ee3c0ab04384..e6c059d20595 100644
--- a/arch/arm64/mm/mem_encrypt.c
+++ b/arch/arm64/mm/mem_encrypt.c
@@ -16,6 +16,7 @@
 #include <linux/bug.h>
 #include <linux/compiler.h>
 #include <linux/err.h>
+#include <linux/cc_shared.h>
 #include <linux/mm.h>
 
 #include <asm/mem_encrypt.h>
@@ -33,7 +34,7 @@ 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)))
+	if (likely(!crypt_ops))
 		return 0;
 
 	return crypt_ops->encrypt(addr, numpages);
@@ -42,9 +43,17 @@ EXPORT_SYMBOL_GPL(set_memory_encrypted);
 
 int set_memory_decrypted(unsigned long addr, int numpages)
 {
-	if (likely(!crypt_ops) || WARN_ON(!PAGE_ALIGNED(addr)))
+	if (likely(!crypt_ops))
 		return 0;
 
 	return crypt_ops->decrypt(addr, numpages);
 }
 EXPORT_SYMBOL_GPL(set_memory_decrypted);
+
+size_t arch_cc_shared_granule_size(void)
+{
+	if (likely(!crypt_ops) || !crypt_ops->shared_granule_size)
+		return PAGE_SIZE;
+
+	return crypt_ops->shared_granule_size();
+}
diff --git a/drivers/firmware/arm_rmm/rsi.c b/drivers/firmware/arm_rmm/rsi.c
index 883f6091ff95..b59099d1f318 100644
--- a/drivers/firmware/arm_rmm/rsi.c
+++ b/drivers/firmware/arm_rmm/rsi.c
@@ -18,6 +18,7 @@
 #include <asm/pgtable.h>
 
 static struct realm_config config;
+static size_t ipa_state_change_alignment = PAGE_SIZE;
 
 unsigned long prot_ns_shared;
 EXPORT_SYMBOL(prot_ns_shared);
@@ -154,9 +155,17 @@ static int realm_set_memory_decrypted(unsigned long addr, int numpages)
 	return ret;
 }
 
+static size_t realm_shared_granule_size(void)
+{
+	if (is_realm_world())
+		return ipa_state_change_alignment;
+	return PAGE_SIZE;
+}
+
 static const struct arm64_mem_crypt_ops realm_crypt_ops = {
 	.encrypt = realm_set_memory_encrypted,
 	.decrypt = realm_set_memory_decrypted,
+	.shared_granule_size = realm_shared_granule_size,
 };
 
 static int realm_register_memory_enc_ops(void)
@@ -166,7 +175,7 @@ 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;
@@ -217,6 +226,8 @@ void __init arm64_rsi_init(void)
 		return;
 	if (WARN_ON(rsi_get_realm_config(lm_alias(&config))))
 		return;
+
+	ipa_state_change_alignment = 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))
-- 
2.43.0