Subject: [PATCH v14 07/44] arm64: RMI: Configure the RMM with the host's page size

From: Steven Price <[email-masked]>
Date: Wed, 13 May 2026 14:17:15 +0100

RMM v2.0 brings the ability to set the RMM's granule size. Check the
feature registers and configure the RMM so that it matches the host's
page size. This means that operations can be done with a granulatity
equal to PAGE_SIZE.

Signed-off-by: Steven Price <[email-masked]>
---
Changes since v13:
 * Moved out of KVM.
---
 arch/arm64/kernel/rmi.c | 42 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/arch/arm64/kernel/rmi.c b/arch/arm64/kernel/rmi.c
index 99c1ccc35c11..a14ead5dedda 100644
--- a/arch/arm64/kernel/rmi.c
+++ b/arch/arm64/kernel/rmi.c
@@ -49,6 +49,45 @@ static int rmi_check_version(void)
 	return 0;
 }
 
+static int rmi_configure(void)
+{
+	struct rmm_config *config __free(free_page) = NULL;
+	unsigned long ret;
+
+	config = (struct rmm_config *)get_zeroed_page(GFP_KERNEL);
+	if (!config)
+		return -ENOMEM;
+
+	switch (PAGE_SIZE) {
+	case SZ_4K:
+		config->rmi_granule_size = RMI_GRANULE_SIZE_4KB;
+		break;
+	case SZ_16K:
+		config->rmi_granule_size = RMI_GRANULE_SIZE_16KB;
+		break;
+	case SZ_64K:
+		config->rmi_granule_size = RMI_GRANULE_SIZE_64KB;
+		break;
+	default:
+		pr_err("Unsupported PAGE_SIZE for RMM\n");
+		return -EINVAL;
+	}
+
+	ret = rmi_rmm_config_set(virt_to_phys(config));
+	if (ret) {
+		pr_err("RMM config set failed\n");
+		return -EINVAL;
+	}
+
+	ret = rmi_rmm_activate();
+	if (ret) {
+		pr_err("RMM activate failed\n");
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
 static int __init arm64_init_rmi(void)
 {
 	/* Continue without realm support if we can't agree on a version */
@@ -60,6 +99,9 @@ static int __init arm64_init_rmi(void)
 	if (WARN_ON(rmi_features(1, &rmm_feat_reg1)))
 		return 0;
 
+	if (rmi_configure())
+		return 0;
+
 	return 0;
 }
 subsys_initcall(arm64_init_rmi);
-- 
2.43.0