[PATCH] KVM: Add system call KVM_VERIFY_MSI to verify MSI vector

[chenxiang]

From: Xiang Chen <chenxiang66@hisilicon.com>

Currently the numbers of MSI vectors come from register PCI_MSI_FLAGS
which should be power-of-2, but in some scenaries it is not the same as
the number that driver requires in guest, for example, a PCI driver wants
to allocate 6 MSI vecotrs in guest, but as the limitation, it will allocate
8 MSI vectors. So it requires 8 MSI vectors in qemu while the driver in
guest only wants to allocate 6 MSI vectors.

When GICv4.1 is enabled, we can see some exception print as following for
above scenaro:
vfio-pci 0000:3a:00.1: irq bypass producer (token 000000008f08224d) 
registration fails:66311

In order to verify whether a MSI vector is valid, add KVM_VERIFY_MSI to do
that. If there is a mapping, return 0, otherwise return negative value.

This is the kernel part of adding system call KVM_VERIFY_MSI.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
---
 arch/arm64/kvm/vgic/vgic-irqfd.c |  5 +++++
 arch/arm64/kvm/vgic/vgic-its.c   | 36 ++++++++++++++++++++++++++++++++++++
 arch/arm64/kvm/vgic/vgic.h       |  1 +
 include/linux/kvm_host.h         |  2 +-
 include/uapi/linux/kvm.h         |  2 ++
 virt/kvm/kvm_main.c              |  9 +++++++++
 6 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/vgic/vgic-irqfd.c b/arch/arm64/kvm/vgic/vgic-irqfd.c
index 475059b..2312da6 100644
--- a/arch/arm64/kvm/vgic/vgic-irqfd.c
+++ b/arch/arm64/kvm/vgic/vgic-irqfd.c
@@ -98,6 +98,11 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
        return vgic_its_inject_msi(kvm, &msi);
 }
 
+int kvm_verify_msi(struct kvm *kvm, struct kvm_msi *msi)
+{
+       return vgic_its_verify_msi(kvm, msi);
+}
+
 /**
  * kvm_arch_set_irq_inatomic: fast-path for irqfd injection
  */
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index 24d7778..cae6183 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -767,6 +767,42 @@ int vgic_its_inject_cached_translation(struct kvm *kvm, 
struct kvm_msi *msi)
        return 0;
 }
 
+int vgic_its_verify_msi(struct kvm *kvm, struct kvm_msi *msi)
+{
+       struct vgic_its *its;
+       struct its_ite *ite;
+       struct kvm_vcpu *vcpu;
+       int ret = 0;
+
+       if (!irqchip_in_kernel(kvm) || (msi->flags & ~KVM_MSI_VALID_DEVID))
+               return -EINVAL;
+
+       if (!vgic_has_its(kvm))
+               return -ENODEV;
+
+       its = vgic_msi_to_its(kvm, msi);
+       if (IS_ERR(its))
+               return PTR_ERR(its);
+
+       mutex_lock(&its->its_lock);
+       if (!its->enabled) {
+               ret = -EBUSY;
+               goto unlock;
+       }
+       ite = find_ite(its, msi->devid, msi->data);
+       if (!ite || !its_is_collection_mapped(ite->collection)) {
+               ret = -E_ITS_INT_UNMAPPED_INTERRUPT;
+               goto unlock;
+       }
+
+       vcpu = kvm_get_vcpu(kvm, ite->collection->target_addr);
+       if (!vcpu)
+               ret = -E_ITS_INT_UNMAPPED_INTERRUPT;
+unlock:
+       mutex_unlock(&its->its_lock);
+       return ret;
+}
+
 /*
  * Queries the KVM IO bus framework to get the ITS pointer from the given
  * doorbell address.
diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index 0c8da72..d452150 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -240,6 +240,7 @@ int kvm_vgic_register_its_device(void);
 void vgic_enable_lpis(struct kvm_vcpu *vcpu);
 void vgic_flush_pending_lpis(struct kvm_vcpu *vcpu);
 int vgic_its_inject_msi(struct kvm *kvm, struct kvm_msi *msi);
+int vgic_its_verify_msi(struct kvm *kvm, struct kvm_msi *msi);
 int vgic_v3_has_attr_regs(struct kvm_device *dev, struct kvm_device_attr 
*attr);
 int vgic_v3_dist_uaccess(struct kvm_vcpu *vcpu, bool is_write,
                         int offset, u32 *val);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 32f259f..7923352 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1597,7 +1597,7 @@ void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
 int kvm_request_irq_source_id(struct kvm *kvm);
 void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id);
 bool kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args);
-
+int kvm_verify_msi(struct kvm *kvm, struct kvm_msi *msi);
 /*
  * Returns a pointer to the memslot if it contains gfn.
  * Otherwise returns NULL.
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 0d5d441..72b28f8 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1543,6 +1543,8 @@ struct kvm_s390_ucas_mapping {
 #define KVM_PPC_SVM_OFF                  _IO(KVMIO,  0xb3)
 #define KVM_ARM_MTE_COPY_TAGS    _IOR(KVMIO,  0xb4, struct 
kvm_arm_copy_mte_tags)
 
+#define KVM_VERIFY_MSI            _IOW(KVMIO,  0xb5, struct kvm_msi)
+
 /* ioctl for vm fd */
 #define KVM_CREATE_DEVICE        _IOWR(KVMIO,  0xe0, struct kvm_create_device)
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e30f1b4..439bdd7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4728,6 +4728,15 @@ static long kvm_vm_ioctl(struct file *filp,
                r = kvm_send_userspace_msi(kvm, &msi);
                break;
        }
+       case KVM_VERIFY_MSI: {
+               struct kvm_msi msi;
+
+               r = -EFAULT;
+               if (copy_from_user(&msi, argp, sizeof(msi)))
+                       goto out;
+               r = kvm_verify_msi(kvm, &msi);
+               break;
+       }
 #endif
 #ifdef __KVM_HAVE_IRQ_LINE
        case KVM_IRQ_LINE_STATUS:
-- 
2.8.1