linux-kernel - [PATCH v9 39/43] arm64: RME: Provide register list for unfinalized RME RECs

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Message-ID: <20250611104844.245235-40-steven.price@arm.com>
Date: Wed, 11 Jun 2025 11:48:36 +0100
From: Steven Price <steven.price@....com>
To: kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Cc: Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>,
	linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
	Gavin Shan <gshan@...hat.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Alper Gun <alpergun@...gle.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
	Emi Kisanuki <fj0570is@...itsu.com>,
	Steven Price <steven.price@....com>
Subject: [PATCH v9 39/43] arm64: RME: Provide register list for unfinalized RME RECs

From: Jean-Philippe Brucker <jean-philippe@...aro.org>

KVM_GET_REG_LIST should not be called before SVE is finalized. The ioctl
handler currently returns -EPERM in this case. But because it uses
kvm_arm_vcpu_is_finalized(), it now also rejects the call for
unfinalized REC even though finalizing the REC can only be done late,
after Realm descriptor creation.

Move the check to copy_sve_reg_indices(). One adverse side effect of
this change is that a KVM_GET_REG_LIST call that only probes for the
array size will now succeed even if SVE is not finalized, but that seems
harmless since the following KVM_GET_REG_LIST with the full array will
fail.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
Signed-off-by: Steven Price <steven.price@....com>
Reviewed-by: Gavin Shan <gshan@...hat.com>
---
 arch/arm64/kvm/arm.c   |  4 ----
 arch/arm64/kvm/guest.c | 10 +++++-----
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 50f039050cfb..7c85f6407775 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1847,10 +1847,6 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		if (unlikely(!kvm_vcpu_initialized(vcpu)))
 			break;
 
-		r = -EPERM;
-		if (!kvm_arm_vcpu_is_finalized(vcpu))
-			break;
-
 		r = -EFAULT;
 		if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
 			break;
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 35847ae03d2c..66637d5097ef 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -675,8 +675,8 @@ static unsigned long num_sve_regs(const struct kvm_vcpu *vcpu)
 	if (!vcpu_has_sve(vcpu))
 		return 0;
 
-	/* Policed by KVM_GET_REG_LIST: */
-	WARN_ON(!kvm_arm_vcpu_sve_finalized(vcpu));
+	if (!kvm_arm_vcpu_sve_finalized(vcpu))
+		return 1; /* KVM_REG_ARM64_SVE_VLS */
 
 	return slices * (SVE_NUM_PREGS + SVE_NUM_ZREGS + 1 /* FFR */)
 		+ 1; /* KVM_REG_ARM64_SVE_VLS */
@@ -693,9 +693,6 @@ static int copy_sve_reg_indices(const struct kvm_vcpu *vcpu,
 	if (!vcpu_has_sve(vcpu))
 		return 0;
 
-	/* Policed by KVM_GET_REG_LIST: */
-	WARN_ON(!kvm_arm_vcpu_sve_finalized(vcpu));
-
 	/*
 	 * Enumerate this first, so that userspace can save/restore in
 	 * the order reported by KVM_GET_REG_LIST:
@@ -705,6 +702,9 @@ static int copy_sve_reg_indices(const struct kvm_vcpu *vcpu,
 		return -EFAULT;
 	++num_regs;
 
+	if (!kvm_arm_vcpu_sve_finalized(vcpu))
+		return num_regs;
+
 	for (i = 0; i < slices; i++) {
 		for (n = 0; n < SVE_NUM_ZREGS; n++) {
 			reg = KVM_REG_ARM64_SVE_ZREG(n, i);
-- 
2.43.0