linux-kernel - [PATCH v2 40/43] arm64: RME: Provide register list for unfinalized RME RECs

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Date: Fri, 12 Apr 2024 09:43:06 +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>,
	Steven Price <steven.price@....com>
Subject: [PATCH v2 40/43] 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>
---
 arch/arm64/kvm/arm.c   | 4 ----
 arch/arm64/kvm/guest.c | 9 +++------
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 69d29797c2ed..2dd014d3c366 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1696,10 +1696,6 @@ 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 d72e59e79185..f1fe51775649 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -652,12 +652,9 @@ static unsigned long num_sve_regs(const struct kvm_vcpu *vcpu)
 {
 	const unsigned int slices = vcpu_sve_slices(vcpu);
 
-	if (!vcpu_has_sve(vcpu))
+	if (!vcpu_has_sve(vcpu) || !kvm_arm_vcpu_sve_finalized(vcpu))
 		return 0;
 
-	/* Policed by KVM_GET_REG_LIST: */
-	WARN_ON(!kvm_arm_vcpu_sve_finalized(vcpu));
-
 	return slices * (SVE_NUM_PREGS + SVE_NUM_ZREGS + 1 /* FFR */)
 		+ 1; /* KVM_REG_ARM64_SVE_VLS */
 }
@@ -673,8 +670,8 @@ 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));
+	if (!kvm_arm_vcpu_sve_finalized(vcpu))
+		return -EPERM;
 
 	/*
 	 * Enumerate this first, so that userspace can save/restore in
-- 
2.34.1