linux-kernel - [PATCH v2 3/4] coco: host: arm64: Handle hostconf RHI calls in kernel

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Message-ID: <20251221160920.297689-4-aneesh.kumar@kernel.org>
Date: Sun, 21 Dec 2025 21:39:19 +0530
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
To: linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev,
	linux-coco@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>,
	will@...nel.org,
	maz@...nel.org,
	tglx@...utronix.de,
	robin.murphy@....com,
	suzuki.poulose@....com,
	akpm@...ux-foundation.org,
	jgg@...pe.ca,
	steven.price@....com,
	"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
Subject: [PATCH v2 3/4] coco: host: arm64: Handle hostconf RHI calls in kernel

 - Mark hostconf RHI SMC IDs as handled in the SMCCC filter.
 - Return version/features plus PAGE_SIZE alignment for guest queries.
 - Drop the 4K page-size guard in RMI init now that realm can query IPA
   change alignment size via the hostconf RHI

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
---
 arch/arm64/kvm/hypercalls.c | 23 ++++++++++++++++++++++-
 arch/arm64/kvm/rmi.c        |  4 ----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 70ac7971416c..2861ca9063dd 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -8,6 +8,7 @@
 
 #include <kvm/arm_hypercalls.h>
 #include <kvm/arm_psci.h>
+#include <asm/rhi.h>
 
 #define KVM_ARM_SMCCC_STD_FEATURES				\
 	GENMASK(KVM_REG_ARM_STD_BMAP_BIT_COUNT - 1, 0)
@@ -77,6 +78,9 @@ static bool kvm_smccc_default_allowed(u32 func_id)
 	 */
 	case ARM_SMCCC_VERSION_FUNC_ID:
 	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
+	case RHI_HOSTCONF_VERSION:
+	case RHI_HOSTCONF_FEATURES:
+	case RHI_HOSTCONF_GET_IPA_CHANGE_ALIGNMENT:
 		return true;
 	default:
 		/* PSCI 0.2 and up is in the 0:0x1f range */
@@ -157,7 +161,15 @@ static int kvm_smccc_filter_insert_reserved(struct kvm *kvm)
 			       GFP_KERNEL_ACCOUNT);
 	if (r)
 		goto out_destroy;
-
+	/*
+	 * Don't forward RHI_HOST_CONF related RHI calls
+	 */
+	r = mtree_insert_range(&kvm->arch.smccc_filter,
+			       RHI_HOSTCONF_VERSION, RHI_HOSTCONF_GET_IPA_CHANGE_ALIGNMENT,
+			       xa_mk_value(KVM_SMCCC_FILTER_HANDLE),
+			       GFP_KERNEL_ACCOUNT);
+	if (r)
+		goto out_destroy;
 	return 0;
 out_destroy:
 	mtree_destroy(&kvm->arch.smccc_filter);
@@ -376,6 +388,15 @@ int kvm_smccc_call_handler(struct kvm_vcpu *vcpu)
 	case ARM_SMCCC_TRNG_RND32:
 	case ARM_SMCCC_TRNG_RND64:
 		return kvm_trng_call(vcpu);
+	case RHI_HOSTCONF_VERSION:
+		val[0] = RHI_HOSTCONF_VER_1_0;
+		break;
+	case RHI_HOSTCONF_FEATURES:
+		val[0] = __RHI_HOSTCONF_GET_IPA_CHANGE_ALIGNMENT;
+		break;
+	case RHI_HOSTCONF_GET_IPA_CHANGE_ALIGNMENT:
+		val[0] = PAGE_SIZE;
+		break;
 	default:
 		return kvm_psci_call(vcpu);
 	}
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index 9957a71d21b1..bd345e051a24 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -1935,10 +1935,6 @@ EXPORT_SYMBOL_GPL(kvm_has_da_feature);
 
 void kvm_init_rmi(void)
 {
-	/* Only 4k page size on the host is supported */
-	if (PAGE_SIZE != SZ_4K)
-		return;
-
 	/* Continue without realm support if we can't agree on a version */
 	if (rmi_check_version())
 		return;
-- 
2.43.0