Re: [PATCH v6 04/11] arm64: rsi: Add support for checking whether an MMIO is protected

On 08/10/2024 01:24, Gavin Shan wrote:

On 10/5/24 12:42 AM, Steven Price wrote:

quoted

From: Suzuki K Poulose <suzuki.poulose@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.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
New patch for v5
---
  arch/arm64/include/asm/io.h       |  8 ++++++++
  arch/arm64/include/asm/rsi.h      |  2 ++
  arch/arm64/include/asm/rsi_cmds.h | 21 +++++++++++++++++++++
  arch/arm64/kernel/rsi.c           | 26 ++++++++++++++++++++++++++
  4 files changed, 57 insertions(+)

With the following nitpick addressed:

Reviewed-by: Gavin Shan <redacted>

quoted

diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index 1ada23a6ec19..cce445ff8e3f 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_mmio_private(phys_addr_t phys_addr,
size_t size)
+{
+    if (unlikely(is_realm_world()))
+        return arm64_is_protected_mmio(phys_addr, size);
+    return false;
+}
+

The function names (arm64_is_{mmio_private, protected_mmio} are
indicators to the
MMIO region's state or property. arm64_is_mmio_private() indicates the
MMIO region
is 'private MMIO' while arm64_is_protected_mmio() indicates the MMIO
region is
'protected MMIO'. They are equivalent and it may be worthy to unify the
function
names (indicators) as below.

  option#1                         option#2
  --------                         --------
  arm64_is_private_mmio            arm64_is_protected_mmio
  __arm64_is_private_mmio          __arm64_is_protected_mmio

Very valid point, I think I prefer option #2 here - "protected" is the
architectural term in CCA.

Thanks,
Steve

quoted

  #endif    /* __ASM_IO_H */

diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
index acba065eb00e..42ff93c7b0ba 100644
--- a/arch/arm64/include/asm/rsi.h
+++ b/arch/arm64/include/asm/rsi.h

@@ -14,6 +14,8 @@ DECLARE_STATIC_KEY_FALSE(rsi_present);

    void __init arm64_rsi_init(void);
  +bool arm64_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 b661331c9204..fdb47f690307 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 a6495a64d9bb..d7bba4cee627 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c

@@ -66,6 +66,32 @@ static void __init arm64_rsi_setup_memory(void)

      }
  }
  +bool arm64_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_DEV)
+            break;
+        base = top;
+    }
+
+    return base >= end;
+}
+EXPORT_SYMBOL(arm64_is_protected_mmio);
+

The function may be worthy to be renamed to __arm64_is_private_mmio, as
explained
as above.

quoted

  void __init arm64_rsi_init(void)
  {
      if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_SMC)

Thanks,
Gavin