[PATCH v5 07/19] arm64: rsi: Add support for checking whether an MMIO is protected

[Steven Price]

From: Suzuki K Poulose <suzuki.poulose at arm.com>

On Arm CCA, with RMM-v1.0, all MMIO regions are shared. However, in
the future, an Arm CCA-v1.0 compliant guest may be run in a lesser
privileged partition in the Realm World (with Arm CCA-v1.1 Planes
feature). In this case, some of the MMIO regions may be emulated
by a higher privileged component in the Realm world, i.e, protected.

Thus the guest must decide today, whether a given MMIO region is shared
vs Protected and create the stage1 mapping accordingly. On Arm CCA, this
detection is based on the "IPA State" (RIPAS == RIPAS_IO). Provide a
helper to run this check on a given range of MMIO.

Also, provide a arm64 helper which may be hooked in by other solutions.

Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Signed-off-by: Steven Price <steven.price at arm.com>
---
New patch for v5
---
 arch/arm64/include/asm/io.h       |  8 ++++++++
 arch/arm64/include/asm/rsi.h      |  3 +++
 arch/arm64/include/asm/rsi_cmds.h | 21 +++++++++++++++++++++
 arch/arm64/kernel/rsi.c           | 26 ++++++++++++++++++++++++++
 4 files changed, 58 insertions(+)

diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index 1ada23a6ec19..a6c551c5e44e 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -17,6 +17,7 @@
 #include <asm/early_ioremap.h>
 #include <asm/alternative.h>
 #include <asm/cpufeature.h>
+#include <asm/rsi.h>
 
 /*
  * Generic IO read/write.  These perform native-endian accesses.
@@ -318,4 +319,11 @@ extern bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
 					unsigned long flags);
 #define arch_memremap_can_ram_remap arch_memremap_can_ram_remap
 
+static inline bool arm64_is_iomem_private(phys_addr_t phys_addr, size_t size)
+{
+	if (unlikely(is_realm_world()))
+		return arm64_rsi_is_protected_mmio(phys_addr, size);
+	return false;
+}
+
 #endif	/* __ASM_IO_H */
diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
index 2bc013badbc3..e31231b50b6a 100644
--- a/arch/arm64/include/asm/rsi.h
+++ b/arch/arm64/include/asm/rsi.h
@@ -13,6 +13,9 @@ DECLARE_STATIC_KEY_FALSE(rsi_present);
 
 void __init arm64_rsi_init(void);
 void __init arm64_rsi_setup_memory(void);
+
+bool arm64_rsi_is_protected_mmio(phys_addr_t base, size_t size);
+
 static inline bool is_realm_world(void)
 {
 	return static_branch_unlikely(&rsi_present);
diff --git a/arch/arm64/include/asm/rsi_cmds.h b/arch/arm64/include/asm/rsi_cmds.h
index 968b03f4e703..c2363f36d167 100644
--- a/arch/arm64/include/asm/rsi_cmds.h
+++ b/arch/arm64/include/asm/rsi_cmds.h
@@ -45,6 +45,27 @@ static inline unsigned long rsi_get_realm_config(struct realm_config *cfg)
 	return res.a0;
 }
 
+static inline unsigned long rsi_ipa_state_get(phys_addr_t start,
+					      phys_addr_t end,
+					      enum ripas *state,
+					      phys_addr_t *top)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(SMC_RSI_IPA_STATE_GET,
+		      start, end, 0, 0, 0, 0, 0,
+		      &res);
+
+	if (res.a0 == RSI_SUCCESS) {
+		if (top)
+			*top = res.a1;
+		if (state)
+			*state = res.a2;
+	}
+
+	return res.a0;
+}
+
 static inline unsigned long rsi_set_addr_range_state(phys_addr_t start,
 						     phys_addr_t end,
 						     enum ripas state,
diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index e968a5c9929e..381a5b9a5333 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -67,6 +67,32 @@ void __init arm64_rsi_setup_memory(void)
 	}
 }
 
+bool arm64_rsi_is_protected_mmio(phys_addr_t base, size_t size)
+{
+	enum ripas ripas;
+	phys_addr_t end, top;
+
+	/* Overflow ? */
+	if (WARN_ON(base + size < base))
+		return false;
+
+	end = ALIGN(base + size, RSI_GRANULE_SIZE);
+	base = ALIGN_DOWN(base, RSI_GRANULE_SIZE);
+
+	while (base < end) {
+		if (WARN_ON(rsi_ipa_state_get(base, end, &ripas, &top)))
+			break;
+		if (WARN_ON(top <= base))
+			break;
+		if (ripas != RSI_RIPAS_IO)
+			break;
+		base = top;
+	}
+
+	return (size && base >= end);
+}
+EXPORT_SYMBOL(arm64_rsi_is_protected_mmio);
+
 void __init arm64_rsi_init(void)
 {
 	/*
-- 
2.34.1