[PATCH 6.6 094/301] KVM: arm64: vgic-v2: Use cpuid from userspace as vcpu_id

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6.6-stable review patch.  If anyone has any objections, please let me know.


From: Marc Zyngier <maz@xxxxxxxxxx>

[ Upstream commit 4e7728c81a54b17bd33be402ac140bc11bb0c4f4 ]

When parsing a GICv2 attribute that contains a cpuid, handle this
as the vcpu_id, not a vcpu_idx, as userspace cannot really know
the mapping between the two. For this, use kvm_get_vcpu_by_id()
instead of kvm_get_vcpu().

Take this opportunity to get rid of the pointless check against
online_vcpus, which doesn't make much sense either, and switch
to FIELD_GET as a way to extract the vcpu_id.

Reviewed-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230927090911.3355209-5-maz@xxxxxxxxxx
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Stable-dep-of: 6ddb4f372fc6 ("KVM: arm64: vgic-v2: Check for non-NULL vCPU in vgic_v2_parse_attr()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
 arch/arm64/kvm/vgic/vgic-kvm-device.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index 212b73a715c1c..c11962f901e0c 100644
--- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
+++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
@@ -339,13 +339,9 @@ int vgic_v2_parse_attr(struct kvm_device *dev, struct kvm_device_attr *attr,
 	int cpuid;
-	cpuid = (attr->attr & KVM_DEV_ARM_VGIC_CPUID_MASK) >>
+	cpuid = FIELD_GET(KVM_DEV_ARM_VGIC_CPUID_MASK, attr->attr);
-	if (cpuid >= atomic_read(&dev->kvm->online_vcpus))
-		return -EINVAL;
-	reg_attr->vcpu = kvm_get_vcpu(dev->kvm, cpuid);
+	reg_attr->vcpu = kvm_get_vcpu_by_id(dev->kvm, cpuid);
 	reg_attr->addr = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
 	return 0;

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