[PATCH v3 0/2] Add SMCCC cache clean/invalidate provider

[PATCH v3 0/2] Add SMCCC cache clean/invalidate provider

[Srirangan Madhavan]

Apologies for the delay in posting v3. We waited until the corresponding
firmware support was available in TF-A. This allowed the provider to be
tested end to end with the CXL Reset series [2].

This series adds an arm64 backend for memregion cache invalidation users
based on the Arm SMCCC cache clean+invalidate interface.

Per DEN0028, this interface targets systems where a Normal Cacheable
memory region can be modified in ways that are not handled by usual PE
coherency mechanisms, and where VA-based CMOs may be too slow or
insufficient for large ranges and/or system-cache implementations.

Representative use cases include device-backed memory state transitions
where stale CPU/system cache lines must be invalidated reliably (for
example secure erase, reset/offline flows, and dynamic memory
reconfiguration).

Patch 1 introduces the Arm SMCCC cache clean/invalidate function IDs and
transient return codes needed by callers [1].

Patch 2 adds a cache maintenance provider that:
- discovers SMCCC support and attributes at init time
- registers with the generic cache coherency framework used by
  cpu_cache_invalidate_memregion()
- handles transient BUSY/RATE_LIMITED responses with bounded retries

This patch set does not add a software fallback path; when firmware does
not implement the SMCCC cache maintenance interface, the provider is not
registered and existing behavior is preserved.

References:
[1] https://developer.arm.com/documentation/den0028/h
[2] https://lore.kernel.org/linux-cxl/20260902072804.665639-1-smadhavan@nvidia.com/

DEN0028 v1.7 has since been confirmed as stable.

Testing:
- With corresponding TF-A support enabled, exercised the provider through
  the CXL Reset path and verified that it invokes the SMCCC call and
  completes the cache flush successfully.
- ARM64 defconfig with CONFIG_CACHEMAINT_FOR_HOTPLUG=y and
  CONFIG_ARM_SMCCC_CACHE=y
- W=1 build of drivers/cache/arm_smccc_cache.o
- W=1 build of the ARM64 Image

Changes since v2:
- Rebased onto Linux v7.3-rc1.
- Preserved the final BUSY or RATE_LIMITED error after retry exhaustion.
- Dropped the redundant feature query for the mandatory ATTRIBUTES call.
- Preserved the full 64-bit maximum-call-rate value returned in X3.
- Reordered local declarations in reverse-fir-tree order.
- Removed the routine provider registration message.

Changes since v1:
- Added Jonathan Cameron's Reviewed-by tags.
- Clarified the ARM_SMCCC_CACHE Kconfig help text.
- Added a Makefile comment identifying the providers that depend on
  CACHEMAINT_FOR_HOTPLUG.
- Dropped the final-backoff-sleep skip in the retry loop.

Changes since RFC:
- Dropped the RFC tag.
- Moved the provider from arch/arm64/mm to drivers/cache.
- Added a dedicated CONFIG_ARM_SMCCC_CACHE option under the existing
  CACHEMAINT_FOR_HOTPLUG menu.
- Dropped the global-operation coalescing optimization.
- Dropped provider handling for SMCCC_RET_NOT_REQUIRED.
- Removed the unnecessary global provider pointer.
- Removed arm64_ prefixes from static provider-local names.
- Documented why these SMCCC Arch cache maintenance calls use SMC64.
- Anchored the SMCCC return-code comment to DEN0028 v1.7.
- Used fsleep() for retry backoff.
- Used unsigned long for retry delay values passed to fsleep().
- Skipped the final backoff sleep when no retry remains.
- Documented the bounded mutex hold time across the serialized retry
  sequence.
- Added mutex_destroy() on the registration failure path.

Srirangan Madhavan (2):
  arm64: smccc: add cache clean/invalidate IDs and return codes
  cache: add SMCCC-backed cache invalidate provider

 drivers/cache/Kconfig           |  11 +++
 drivers/cache/Makefile          |   2 +
 drivers/cache/arm_smccc_cache.c | 149 ++++++++++++++++++++++++++++++++
 include/linux/arm-smccc.h       |  21 ++++-
 tools/include/linux/arm-smccc.h |  21 ++++-
 5 files changed, 200 insertions(+), 4 deletions(-)
 create mode 100644 drivers/cache/arm_smccc_cache.c


base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
-- 
2.43.0

[PATCH v3 1/2] arm64: smccc: add cache clean/invalidate IDs and return codes

[Srirangan Madhavan]

Define SMCCC Arch function IDs for CLEAN_INV_MEMREGION and its ATTRIBUTES
call, and add RATE_LIMITED/BUSY return codes from DEN0028 for callers that
need transient error handling.

Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
Reviewed-by: Jonathan Cameron <jic23@kernel.org>
---
 include/linux/arm-smccc.h       | 21 +++++++++++++++++++--
 tools/include/linux/arm-smccc.h | 21 +++++++++++++++++++--
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 4de81848fe2e..2e205320d88a 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -116,6 +116,22 @@
 			   ARM_SMCCC_SMC_32,				\
 			   ARM_SMCCC_OWNER_CPU, 0x10)
 
+/*
+ * DEN0028 v1.7 defines these cache maintenance functions as SMC64
+ * because they carry 64-bit memory range arguments.
+ */
+#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_64,				\
+			   ARM_SMCCC_OWNER_ARCH,			\
+			   0x5)
+
+#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES			\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_64,				\
+			   ARM_SMCCC_OWNER_ARCH,			\
+			   0x6)
+
 #define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID				\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
 			   ARM_SMCCC_SMC_32,				\
@@ -305,13 +321,14 @@
 			   0x53)
 
 /*
- * Return codes defined in ARM DEN 0070A
- * ARM DEN 0070A is now merged/consolidated into ARM DEN 0028 C
+ * Return codes defined by Arm SMCCC (DEN0028 v1.7).
  */
 #define SMCCC_RET_SUCCESS			0
 #define SMCCC_RET_NOT_SUPPORTED			-1
 #define SMCCC_RET_NOT_REQUIRED			-2
 #define SMCCC_RET_INVALID_PARAMETER		-3
+#define SMCCC_RET_RATE_LIMITED			-4
+#define SMCCC_RET_BUSY				-5
 
 #ifndef __ASSEMBLY__
 
diff --git a/tools/include/linux/arm-smccc.h b/tools/include/linux/arm-smccc.h
index 63ce9bebccd3..ae5637b3240f 100644
--- a/tools/include/linux/arm-smccc.h
+++ b/tools/include/linux/arm-smccc.h
@@ -96,6 +96,22 @@
 			   ARM_SMCCC_SMC_32,				\
 			   0, 0x3fff)
 
+/*
+ * DEN0028 v1.7 defines these cache maintenance functions as SMC64
+ * because they carry 64-bit memory range arguments.
+ */
+#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_64,				\
+			   ARM_SMCCC_OWNER_ARCH,			\
+			   0x5)
+
+#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES			\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_64,				\
+			   ARM_SMCCC_OWNER_ARCH,			\
+			   0x6)
+
 #define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID				\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
 			   ARM_SMCCC_SMC_32,				\
@@ -182,12 +198,13 @@
 			   0x53)
 
 /*
- * Return codes defined in ARM DEN 0070A
- * ARM DEN 0070A is now merged/consolidated into ARM DEN 0028 C
+ * Return codes defined by Arm SMCCC (DEN0028 v1.7).
  */
 #define SMCCC_RET_SUCCESS			0
 #define SMCCC_RET_NOT_SUPPORTED			-1
 #define SMCCC_RET_NOT_REQUIRED			-2
 #define SMCCC_RET_INVALID_PARAMETER		-3
+#define SMCCC_RET_RATE_LIMITED			-4
+#define SMCCC_RET_BUSY				-5
 
 #endif /*__LINUX_ARM_SMCCC_H*/
-- 
2.43.0

Re: [PATCH v3 1/2] arm64: smccc: add cache clean/invalidate IDs and return codes

[Andre Przywara]

Hi,

On 9/10/26 10:21, Srirangan Madhavan wrote:
> Define SMCCC Arch function IDs for CLEAN_INV_MEMREGION and its ATTRIBUTES
> call, and add RATE_LIMITED/BUSY return codes from DEN0028 for callers that
> need transient error handling.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> Reviewed-by: Jonathan Cameron <jic23@kernel.org>
> ---
>   include/linux/arm-smccc.h       | 21 +++++++++++++++++++--
>   tools/include/linux/arm-smccc.h | 21 +++++++++++++++++++--
>   2 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 4de81848fe2e..2e205320d88a 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.hARM_SMCCC_FAST_CALL
> @@ -116,6 +116,22 @@
>   			   ARM_SMCCC_SMC_32,				\
>   			   ARM_SMCCC_OWNER_CPU, 0x10)
>   
> +/*
> + * DEN0028 v1.7 defines these cache maintenance functions as SMC64
> + * because they carry 64-bit memory range arguments.
> + */
> +#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION				\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_ARCH,			\
> +			   0x5)
> +
> +#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES			\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_ARCH,			\
> +			   0x6)
> +
>   #define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID				\
>   	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
>   			   ARM_SMCCC_SMC_32,				\
> @@ -305,13 +321,14 @@
>   			   0x53)
>   
>   /*
> - * Return codes defined in ARM DEN 0070A
> - * ARM DEN 0070A is now merged/consolidated into ARM DEN 0028 C
> + * Return codes defined by Arm SMCCC (DEN0028 v1.7).
>    */
>   #define SMCCC_RET_SUCCESS			0
>   #define SMCCC_RET_NOT_SUPPORTED			-1
>   #define SMCCC_RET_NOT_REQUIRED			-2
>   #define SMCCC_RET_INVALID_PARAMETER		-3
> +#define SMCCC_RET_RATE_LIMITED			-4
> +#define SMCCC_RET_BUSY				-5
>   
>   #ifndef __ASSEMBLY__
>   
> diff --git a/tools/include/linux/arm-smccc.h b/tools/include/linux/arm-smccc.h
> index 63ce9bebccd3..ae5637b3240f 100644
> --- a/tools/include/linux/arm-smccc.h
> +++ b/tools/include/linux/arm-smccc.h

Why is that? Is there any tool using that? I don't think we 
unconditionally sync the two files?

The numbers in the file above match the spec, so for that part:

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre


> @@ -96,6 +96,22 @@
>   			   ARM_SMCCC_SMC_32,				\
>   			   0, 0x3fff)
>   
> +/*
> + * DEN0028 v1.7 defines these cache maintenance functions as SMC64
> + * because they carry 64-bit memory range arguments.
> + */
> +#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION				\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_ARCH,			\
> +			   0x5)
> +
> +#define ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES			\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_ARCH,			\
> +			   0x6)
> +
>   #define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID				\
>   	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
>   			   ARM_SMCCC_SMC_32,				\
> @@ -182,12 +198,13 @@
>   			   0x53)
>   
>   /*
> - * Return codes defined in ARM DEN 0070A
> - * ARM DEN 0070A is now merged/consolidated into ARM DEN 0028 C
> + * Return codes defined by Arm SMCCC (DEN0028 v1.7).
>    */
>   #define SMCCC_RET_SUCCESS			0
>   #define SMCCC_RET_NOT_SUPPORTED			-1
>   #define SMCCC_RET_NOT_REQUIRED			-2
>   #define SMCCC_RET_INVALID_PARAMETER		-3
> +#define SMCCC_RET_RATE_LIMITED			-4
> +#define SMCCC_RET_BUSY				-5
>   
>   #endif /*__LINUX_ARM_SMCCC_H*/

[PATCH v3 2/2] cache: add SMCCC-backed cache invalidate provider

[Srirangan Madhavan]

Add a cache maintenance provider for the Arm SMCCC cache clean+invalidate
interface.

The provider discovers SMCCC support and attributes at init time,
serializes firmware calls, handles transient BUSY and RATE_LIMITED
responses with bounded retries, and registers with the generic cache
coherency framework used by memregion callers.

Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
Reviewed-by: Jonathan Cameron <jic23@kernel.org>
---
 drivers/cache/Kconfig           |  11 +++
 drivers/cache/Makefile          |   2 +
 drivers/cache/arm_smccc_cache.c | 149 ++++++++++++++++++++++++++++++++
 3 files changed, 162 insertions(+)
 create mode 100644 drivers/cache/arm_smccc_cache.c

diff --git a/drivers/cache/Kconfig b/drivers/cache/Kconfig
index 1518449d47b5..57fd1823dec5 100644
--- a/drivers/cache/Kconfig
+++ b/drivers/cache/Kconfig
@@ -42,6 +42,17 @@ menuconfig CACHEMAINT_FOR_HOTPLUG
 
 if CACHEMAINT_FOR_HOTPLUG
 
+config ARM_SMCCC_CACHE
+	bool "Arm SMCCC cache maintenance provider"
+	depends on ARM64 && HAVE_ARM_SMCCC_DISCOVERY
+	help
+	  Enable support for the Arm SMCCC cache clean+invalidate
+	  interface as a provider for memory hotplug-like cache
+	  maintenance operations.
+	  The provider registers only when firmware advertises the
+	  SMCCC calls and attributes, so systems without firmware support
+	  continue without this registered provider.
+
 config HISI_SOC_HHA
 	tristate "HiSilicon Hydra Home Agent (HHA) device driver"
 	depends on (ARM64 && ACPI) || COMPILE_TEST
diff --git a/drivers/cache/Makefile b/drivers/cache/Makefile
index b3362b15d6c1..55736a032d6f 100644
--- a/drivers/cache/Makefile
+++ b/drivers/cache/Makefile
@@ -4,4 +4,6 @@ obj-$(CONFIG_AX45MP_L2_CACHE)		+= ax45mp_cache.o
 obj-$(CONFIG_SIFIVE_CCACHE)		+= sifive_ccache.o
 obj-$(CONFIG_STARFIVE_STARLINK_CACHE)	+= starfive_starlink_cache.o
 
+# Providers below depend on CACHEMAINT_FOR_HOTPLUG.
+obj-$(CONFIG_ARM_SMCCC_CACHE)		+= arm_smccc_cache.o
 obj-$(CONFIG_HISI_SOC_HHA)		+= hisi_soc_hha.o
diff --git a/drivers/cache/arm_smccc_cache.c b/drivers/cache/arm_smccc_cache.c
new file mode 100644
index 000000000000..1cfa8f8809d0
--- /dev/null
+++ b/drivers/cache/arm_smccc_cache.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2026 NVIDIA Corporation
+ *
+ * Arm SMCCC cache maintenance provider using cache clean+invalidate calls.
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/cache_coherency.h>
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+#include <linux/nmi.h>
+
+#define SMCCC_CACHE_MAX_RETRIES		5
+#define SMCCC_CACHE_DEFAULT_DELAY_US	1000UL
+#define SMCCC_CACHE_MAX_DELAY_US	20000UL
+
+struct smccc_cache {
+	/* Must be first member */
+	struct cache_coherency_ops_inst cci;
+	struct mutex lock; /* Serializes SMCCC cache maintenance calls. */
+	u64 rate_limit;
+	u32 latency_us;
+};
+
+static int smccc_cache_status_to_errno(s32 status)
+{
+	switch (status) {
+	case SMCCC_RET_SUCCESS:
+		return 0;
+	case SMCCC_RET_NOT_SUPPORTED:
+		return -EOPNOTSUPP;
+	case SMCCC_RET_INVALID_PARAMETER:
+		return -EINVAL;
+	case SMCCC_RET_RATE_LIMITED:
+		return -EAGAIN;
+	case SMCCC_RET_BUSY:
+		return -EBUSY;
+	default:
+		return -EIO;
+	}
+}
+
+static unsigned long smccc_cache_delay_us(const struct smccc_cache *cache)
+{
+	unsigned long delay_us = 0;
+
+	if (cache->rate_limit)
+		delay_us = DIV_ROUND_UP_ULL(USEC_PER_SEC, cache->rate_limit);
+
+	if (cache->latency_us)
+		delay_us = max(delay_us, (unsigned long)cache->latency_us);
+
+	/*
+	 * Firmware may advertise neither a rate limit nor a latency hint; use
+	 * a small bounded backoff instead of retrying in a tight loop.
+	 */
+	if (!delay_us)
+		delay_us = SMCCC_CACHE_DEFAULT_DELAY_US;
+
+	return min(delay_us, SMCCC_CACHE_MAX_DELAY_US);
+}
+
+static int smccc_cache_wbinv(struct cache_coherency_ops_inst *cci,
+			     struct cc_inval_params *invp)
+{
+	struct smccc_cache *cache = container_of(cci, struct smccc_cache, cci);
+	unsigned long delay_us = smccc_cache_delay_us(cache);
+	struct arm_smccc_res res = {};
+	int ret;
+
+	if (!invp->size)
+		return -EINVAL;
+
+	/*
+	 * Serialize the full retry sequence. With the default bounds, a caller
+	 * may hold the mutex across up to five 20ms backoff sleeps.
+	 */
+	guard(mutex)(&cache->lock);
+
+	for (unsigned int i = 0; i < SMCCC_CACHE_MAX_RETRIES; i++) {
+		/* Long firmware operations can trigger watchdog checks. */
+		touch_nmi_watchdog();
+
+		arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION,
+				     invp->addr, invp->size, 0UL, &res);
+
+		ret = smccc_cache_status_to_errno((s32)res.a0);
+		if (!ret)
+			return 0;
+
+		if (ret != -EBUSY && ret != -EAGAIN)
+			return ret;
+
+		fsleep(delay_us);
+	}
+
+	return ret;
+}
+
+static const struct cache_coherency_ops smccc_cache_ops = {
+	.wbinv = smccc_cache_wbinv,
+};
+
+static int __init smccc_cache_init(void)
+{
+	struct arm_smccc_res res = {};
+	struct smccc_cache *cache;
+	int ret;
+
+	if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_1)
+		return -ENODEV;
+
+	if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
+		return -ENODEV;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+			     ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION, &res);
+	if ((s32)res.a0 < 0)
+		return -ENODEV;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES,
+			     &res);
+	if ((s32)res.a0)
+		return -ENODEV;
+
+	cache = cache_coherency_ops_instance_alloc(&smccc_cache_ops,
+						   struct smccc_cache, cci);
+	if (!cache)
+		return -ENOMEM;
+
+	mutex_init(&cache->lock);
+	cache->latency_us = lower_32_bits(res.a2);
+	cache->rate_limit = res.a3;
+
+	ret = cache_coherency_ops_instance_register(&cache->cci);
+	if (ret) {
+		mutex_destroy(&cache->lock);
+		cache_coherency_ops_instance_put(&cache->cci);
+		return ret;
+	}
+
+	return 0;
+}
+arch_initcall(smccc_cache_init);
-- 
2.43.0

Re: [PATCH v3 2/2] cache: add SMCCC-backed cache invalidate provider

[Jonathan Cameron]

On Thu, 10 Sep 2026 08:21:42 +0000
Srirangan Madhavan <smadhavan@nvidia.com> wrote:

> Add a cache maintenance provider for the Arm SMCCC cache clean+invalidate
> interface.
> 
> The provider discovers SMCCC support and attributes at init time,
> serializes firmware calls, handles transient BUSY and RATE_LIMITED
> responses with bounded retries, and registers with the generic cache
> coherency framework used by memregion callers.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> Reviewed-by: Jonathan Cameron <jic23@kernel.org>

One tiny thing inline.

Thanks,

Jonathan


> diff --git a/drivers/cache/arm_smccc_cache.c b/drivers/cache/arm_smccc_cache.c
> new file mode 100644
> index 000000000000..1cfa8f8809d0
> --- /dev/null
> +++ b/drivers/cache/arm_smccc_cache.c
> @@ -0,0 +1,149 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2026 NVIDIA Corporation
> + *
> + * Arm SMCCC cache maintenance provider using cache clean+invalidate calls.
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/cache_coherency.h>
> +#include <linux/cleanup.h>
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>

Small thing, but can we avoid including the catch all that is kernel.h.
Generally aim for more specific headers for what is actually used.

> +#include <linux/mutex.h>
> +#include <linux/nmi.h>
> +

Re: [PATCH v3 2/2] cache: add SMCCC-backed cache invalidate provider

[Conor Dooley]

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Will/Catalin,

On Thu, Sep 10, 2026 at 08:21:42AM +0000, Srirangan Madhavan wrote:
> Add a cache maintenance provider for the Arm SMCCC cache clean+invalidate
> interface.
> 
> The provider discovers SMCCC support and attributes at init time,
> serializes firmware calls, handles transient BUSY and RATE_LIMITED
> responses with bounded retries, and registers with the generic cache
> coherency framework used by memregion callers.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> Reviewed-by: Jonathan Cameron <jic23@kernel.org>

If yous wanna take this,
Acked-by: Conor Dooley <conor.dooley@microchip.com>

Cheers,
Conor.

[-- Attachment #2: signature.asc --]
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Re: [PATCH v3 2/2] cache: add SMCCC-backed cache invalidate provider

[Andre Przywara]

Hi,

On 9/10/26 10:21, Srirangan Madhavan wrote:
> Add a cache maintenance provider for the Arm SMCCC cache clean+invalidate
> interface.
> 
> The provider discovers SMCCC support and attributes at init time,
> serializes firmware calls, handles transient BUSY and RATE_LIMITED
> responses with bounded retries, and registers with the generic cache
> coherency framework used by memregion callers.

Is there any chance you could hook this up to the new Arm SMCCC bus? 
Looks like Aneesh's series[1] is now queued for v7.4. You would just 
need to pick the first two patches, then replicate the work that's done 
in patch 2/8.

The rest looks okay on a first glance, but can you please mention the 
respective spec document (Arm DEN0028) somewhere, ideally at the top of 
the file and maybe in the commit message?

Cheers,
Andre

[1] 
https://lore.kernel.org/linux-arm-kernel/179026658584.3654431.7189876471375206962.b4-ty@b4/

> 
> Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> Reviewed-by: Jonathan Cameron <jic23@kernel.org>
> ---
>   drivers/cache/Kconfig           |  11 +++
>   drivers/cache/Makefile          |   2 +
>   drivers/cache/arm_smccc_cache.c | 149 ++++++++++++++++++++++++++++++++
>   3 files changed, 162 insertions(+)
>   create mode 100644 drivers/cache/arm_smccc_cache.c
> 
> diff --git a/drivers/cache/Kconfig b/drivers/cache/Kconfig
> index 1518449d47b5..57fd1823dec5 100644
> --- a/drivers/cache/Kconfig
> +++ b/drivers/cache/Kconfig
> @@ -42,6 +42,17 @@ menuconfig CACHEMAINT_FOR_HOTPLUG
>   
>   if CACHEMAINT_FOR_HOTPLUG
>   
> +config ARM_SMCCC_CACHE
> +	bool "Arm SMCCC cache maintenance provider"
> +	depends on ARM64 && HAVE_ARM_SMCCC_DISCOVERY
> +	help
> +	  Enable support for the Arm SMCCC cache clean+invalidate
> +	  interface as a provider for memory hotplug-like cache
> +	  maintenance operations.
> +	  The provider registers only when firmware advertises the
> +	  SMCCC calls and attributes, so systems without firmware support
> +	  continue without this registered provider.
> +
>   config HISI_SOC_HHA
>   	tristate "HiSilicon Hydra Home Agent (HHA) device driver"
>   	depends on (ARM64 && ACPI) || COMPILE_TEST
> diff --git a/drivers/cache/Makefile b/drivers/cache/Makefile
> index b3362b15d6c1..55736a032d6f 100644
> --- a/drivers/cache/Makefile
> +++ b/drivers/cache/Makefile
> @@ -4,4 +4,6 @@ obj-$(CONFIG_AX45MP_L2_CACHE)		+= ax45mp_cache.o
>   obj-$(CONFIG_SIFIVE_CCACHE)		+= sifive_ccache.o
>   obj-$(CONFIG_STARFIVE_STARLINK_CACHE)	+= starfive_starlink_cache.o
>   
> +# Providers below depend on CACHEMAINT_FOR_HOTPLUG.
> +obj-$(CONFIG_ARM_SMCCC_CACHE)		+= arm_smccc_cache.o
>   obj-$(CONFIG_HISI_SOC_HHA)		+= hisi_soc_hha.o
> diff --git a/drivers/cache/arm_smccc_cache.c b/drivers/cache/arm_smccc_cache.c
> new file mode 100644
> index 000000000000..1cfa8f8809d0
> --- /dev/null
> +++ b/drivers/cache/arm_smccc_cache.c
> @@ -0,0 +1,149 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2026 NVIDIA Corporation
> + *
> + * Arm SMCCC cache maintenance provider using cache clean+invalidate calls.
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/cache_coherency.h>
> +#include <linux/cleanup.h>
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/mutex.h>
> +#include <linux/nmi.h>
> +
> +#define SMCCC_CACHE_MAX_RETRIES		5
> +#define SMCCC_CACHE_DEFAULT_DELAY_US	1000UL
> +#define SMCCC_CACHE_MAX_DELAY_US	20000UL
> +
> +struct smccc_cache {
> +	/* Must be first member */
> +	struct cache_coherency_ops_inst cci;
> +	struct mutex lock; /* Serializes SMCCC cache maintenance calls. */
> +	u64 rate_limit;
> +	u32 latency_us;
> +};
> +
> +static int smccc_cache_status_to_errno(s32 status)
> +{
> +	switch (status) {
> +	case SMCCC_RET_SUCCESS:
> +		return 0;
> +	case SMCCC_RET_NOT_SUPPORTED:
> +		return -EOPNOTSUPP;
> +	case SMCCC_RET_INVALID_PARAMETER:
> +		return -EINVAL;
> +	case SMCCC_RET_RATE_LIMITED:
> +		return -EAGAIN;
> +	case SMCCC_RET_BUSY:
> +		return -EBUSY;
> +	default:
> +		return -EIO;
> +	}
> +}
> +
> +static unsigned long smccc_cache_delay_us(const struct smccc_cache *cache)
> +{
> +	unsigned long delay_us = 0;
> +
> +	if (cache->rate_limit)
> +		delay_us = DIV_ROUND_UP_ULL(USEC_PER_SEC, cache->rate_limit);
> +
> +	if (cache->latency_us)
> +		delay_us = max(delay_us, (unsigned long)cache->latency_us);
> +
> +	/*
> +	 * Firmware may advertise neither a rate limit nor a latency hint; use
> +	 * a small bounded backoff instead of retrying in a tight loop.
> +	 */
> +	if (!delay_us)
> +		delay_us = SMCCC_CACHE_DEFAULT_DELAY_US;
> +
> +	return min(delay_us, SMCCC_CACHE_MAX_DELAY_US);
> +}
> +
> +static int smccc_cache_wbinv(struct cache_coherency_ops_inst *cci,
> +			     struct cc_inval_params *invp)
> +{
> +	struct smccc_cache *cache = container_of(cci, struct smccc_cache, cci);
> +	unsigned long delay_us = smccc_cache_delay_us(cache);
> +	struct arm_smccc_res res = {};
> +	int ret;
> +
> +	if (!invp->size)
> +		return -EINVAL;
> +
> +	/*
> +	 * Serialize the full retry sequence. With the default bounds, a caller
> +	 * may hold the mutex across up to five 20ms backoff sleeps.
> +	 */
> +	guard(mutex)(&cache->lock);
> +
> +	for (unsigned int i = 0; i < SMCCC_CACHE_MAX_RETRIES; i++) {
> +		/* Long firmware operations can trigger watchdog checks. */
> +		touch_nmi_watchdog();
> +
> +		arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION,
> +				     invp->addr, invp->size, 0UL, &res);
> +
> +		ret = smccc_cache_status_to_errno((s32)res.a0);
> +		if (!ret)
> +			return 0;
> +
> +		if (ret != -EBUSY && ret != -EAGAIN)
> +			return ret;
> +
> +		fsleep(delay_us);
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct cache_coherency_ops smccc_cache_ops = {
> +	.wbinv = smccc_cache_wbinv,
> +};
> +
> +static int __init smccc_cache_init(void)
> +{
> +	struct arm_smccc_res res = {};
> +	struct smccc_cache *cache;
> +	int ret;
> +
> +	if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_1)
> +		return -ENODEV;
> +
> +	if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
> +		return -ENODEV;
> +
> +	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
> +			     ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION, &res);
> +	if ((s32)res.a0 < 0)
> +		return -ENODEV;
> +
> +	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES,
> +			     &res);
> +	if ((s32)res.a0)
> +		return -ENODEV;
> +
> +	cache = cache_coherency_ops_instance_alloc(&smccc_cache_ops,
> +						   struct smccc_cache, cci);
> +	if (!cache)
> +		return -ENOMEM;
> +
> +	mutex_init(&cache->lock);
> +	cache->latency_us = lower_32_bits(res.a2);
> +	cache->rate_limit = res.a3;
> +
> +	ret = cache_coherency_ops_instance_register(&cache->cci);
> +	if (ret) {
> +		mutex_destroy(&cache->lock);
> +		cache_coherency_ops_instance_put(&cache->cci);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +arch_initcall(smccc_cache_init);

Re: [PATCH v3 0/2] Add SMCCC cache clean/invalidate provider

[Bence Csókás]

Hi,

On 2026. 09. 10. 10:21, Srirangan Madhavan wrote:
> Apologies for the delay in posting v3. We waited until the corresponding
> firmware support was available in TF-A. This allowed the provider to be
> tested end to end with the CXL Reset series [2].
> 
> This series adds an arm64 backend for memregion cache invalidation users
> based on the Arm SMCCC cache clean+invalidate interface.
> 
> Per DEN0028, this interface targets systems where a Normal Cacheable
> memory region can be modified in ways that are not handled by usual PE
> coherency mechanisms, and where VA-based CMOs may be too slow or
> insufficient for large ranges and/or system-cache implementations.
> 
> Representative use cases include device-backed memory state transitions
> where stale CPU/system cache lines must be invalidated reliably (for
> example secure erase, reset/offline flows, and dynamic memory
> reconfiguration).
> 
> Patch 1 introduces the Arm SMCCC cache clean/invalidate function IDs and
> transient return codes needed by callers [1].
> 
> Patch 2 adds a cache maintenance provider that:
> - discovers SMCCC support and attributes at init time
> - registers with the generic cache coherency framework used by
>    cpu_cache_invalidate_memregion()
> - handles transient BUSY/RATE_LIMITED responses with bounded retries
> 
> This patch set does not add a software fallback path; when firmware does
> not implement the SMCCC cache maintenance interface, the provider is not
> registered and existing behavior is preserved.
> 
> References:
> [1] https://developer.arm.com/documentation/den0028/h
> [2] https://lore.kernel.org/linux-cxl/20260902072804.665639-1-smadhavan@nvidia.com/
> 
> DEN0028 v1.7 has since been confirmed as stable.
> 
> Testing:
> - With corresponding TF-A support enabled, exercised the provider through
>    the CXL Reset path and verified that it invokes the SMCCC call and
>    completes the cache flush successfully.
> - ARM64 defconfig with CONFIG_CACHEMAINT_FOR_HOTPLUG=y and
>    CONFIG_ARM_SMCCC_CACHE=y
> - W=1 build of drivers/cache/arm_smccc_cache.o
> - W=1 build of the ARM64 Image
> 
> Changes since v2:
> - Rebased onto Linux v7.3-rc1.
> - Preserved the final BUSY or RATE_LIMITED error after retry exhaustion.
> - Dropped the redundant feature query for the mandatory ATTRIBUTES call.
> - Preserved the full 64-bit maximum-call-rate value returned in X3.
> - Reordered local declarations in reverse-fir-tree order.
> - Removed the routine provider registration message.

Reviewed-by: Bence Csókás <bence.csokas@arm.com>

I have yet to try it out on actual hardware, but from looking at the 
code, it now seems to match the spec.

> Changes since v1:
> - Added Jonathan Cameron's Reviewed-by tags.
> - Clarified the ARM_SMCCC_CACHE Kconfig help text.
> - Added a Makefile comment identifying the providers that depend on
>    CACHEMAINT_FOR_HOTPLUG.
> - Dropped the final-backoff-sleep skip in the retry loop.
> 
> Changes since RFC:
> - Dropped the RFC tag.
> - Moved the provider from arch/arm64/mm to drivers/cache.
> - Added a dedicated CONFIG_ARM_SMCCC_CACHE option under the existing
>    CACHEMAINT_FOR_HOTPLUG menu.
> - Dropped the global-operation coalescing optimization.
> - Dropped provider handling for SMCCC_RET_NOT_REQUIRED.
> - Removed the unnecessary global provider pointer.
> - Removed arm64_ prefixes from static provider-local names.
> - Documented why these SMCCC Arch cache maintenance calls use SMC64.
> - Anchored the SMCCC return-code comment to DEN0028 v1.7.
> - Used fsleep() for retry backoff.
> - Used unsigned long for retry delay values passed to fsleep().
> - Skipped the final backoff sleep when no retry remains.
> - Documented the bounded mutex hold time across the serialized retry
>    sequence.
> - Added mutex_destroy() on the registration failure path.
> 
> Srirangan Madhavan (2):
>    arm64: smccc: add cache clean/invalidate IDs and return codes
>    cache: add SMCCC-backed cache invalidate provider
> 
>   drivers/cache/Kconfig           |  11 +++
>   drivers/cache/Makefile          |   2 +
>   drivers/cache/arm_smccc_cache.c | 149 ++++++++++++++++++++++++++++++++
>   include/linux/arm-smccc.h       |  21 ++++-
>   tools/include/linux/arm-smccc.h |  21 ++++-
>   5 files changed, 200 insertions(+), 4 deletions(-)
>   create mode 100644 drivers/cache/arm_smccc_cache.c
> 
> 
> base-commit: cee9395acd8043be0644b25c34bfa86623f2b935

Bence