Re: [PATCH v7 20/22] KVM: s390: add KVM_S390_ZPCI_OP to manage guest zPCI devices

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On 5/16/22 5:52 AM, Thomas Huth wrote:
On 13/05/2022 21.15, Matthew Rosato wrote:
The KVM_S390_ZPCI_OP ioctl provides a mechanism for managing
hardware-assisted virtualization features for s390X zPCI passthrough.

s/s390X/s390x/

Add the first 2 operations, which can be used to enable/disable
the specified device for Adapter Event Notification interpretation.

Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
  Documentation/virt/kvm/api.rst | 45 +++++++++++++++++++
  arch/s390/kvm/kvm-s390.c       | 23 ++++++++++
  arch/s390/kvm/pci.c            | 81 ++++++++++++++++++++++++++++++++++
  arch/s390/kvm/pci.h            |  2 +
  include/uapi/linux/kvm.h       | 31 +++++++++++++
  5 files changed, 182 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 4a900cdbc62e..a7cd5ebce031 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5645,6 +5645,51 @@ enabled with ``arch_prctl()``, but this may change in the future.   The offsets of the state save areas in struct kvm_xsave follow the contents
  of CPUID leaf 0xD on the host.
+4.135 KVM_S390_ZPCI_OP
+--------------------
+
+:Capability: KVM_CAP_S390_ZPCI_OP
+:Architectures: s390
+:Type: vcpu ioctl

vcpu? ... you're wiring it up in  kvm_arch_vm_ioctl() later, so I assume it's rather a VM ioctl?

Yup, VM ioctl, bad copy/paste job...


+:Parameters: struct kvm_s390_zpci_op (in)
+:Returns: 0 on success, <0 on error
+
+Used to manage hardware-assisted virtualization features for zPCI devices.
+
+Parameters are specified via the following structure::
+
+  struct kvm_s390_zpci_op {
+    /* in */

If all is "in", why is there a copy_to_user() in the code later?


Oh no, this is a leftover from a prior version... Good catch. There should no longer be a copy_to_user.

+    __u32 fh;        /* target device */
+    __u8  op;        /* operation to perform */
+    __u8  pad[3];
+    union {
+        /* for KVM_S390_ZPCIOP_REG_AEN */
+        struct {
+            __u64 ibv;    /* Guest addr of interrupt bit vector */
+            __u64 sb;    /* Guest addr of summary bit */

If this is really a vcpu ioctl, what kind of addresses are you talking about here? virtual addresses? real addresses? absolute addresses?

It's a VM ioctl. These are guest kernel physical addresses that are later pinned in arch/s390/kvm/pci.c:kvm_s390_pci_aif_enable() as part of handling the ioctl.


+            __u32 flags;
+            __u32 noi;    /* Number of interrupts */
+            __u8 isc;    /* Guest interrupt subclass */
+            __u8 sbo;    /* Offset of guest summary bit vector */
+            __u16 pad;
+        } reg_aen;
+        __u64 reserved[8];
+    } u;
+  };
+
+The type of operation is specified in the "op" field.
+KVM_S390_ZPCIOP_REG_AEN is used to register the VM for adapter event
+notification interpretation, which will allow firmware delivery of adapter +events directly to the vm, with KVM providing a backup delivery mechanism; +KVM_S390_ZPCIOP_DEREG_AEN is used to subsequently disable interpretation of
+adapter event notifications.
+
+The target zPCI function must also be specified via the "fh" field. For the +KVM_S390_ZPCIOP_REG_AEN operation, additional information to establish firmware
+delivery must be provided via the "reg_aen" struct.
+
+The "reserved" field is meant for future extensions.

Maybe also mention the "pad" fields? And add should these also be initialized to 0 by the calling userspace program?

Sure, I can mention them. And yes, I agree that userspace should initialize them to 0, I'll update the QEMU series accordingly.


  5. The kvm_run structure
  ========================
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b95b25490018..1af7cea9d579 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -618,6 +618,12 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
      case KVM_CAP_S390_PROTECTED:
          r = is_prot_virt_host();
          break;
+    case KVM_CAP_S390_ZPCI_OP:
+        if (kvm_s390_pci_interp_allowed())
+            r = 1;
+        else
+            r = 0;

Could be shortened to:

         r = kvm_s390_pci_interp_allowed();

+        break;
      default:
          r = 0;
      }
@@ -2633,6 +2639,23 @@ long kvm_arch_vm_ioctl(struct file *filp,
              r = -EFAULT;
          break;
      }
+    case KVM_S390_ZPCI_OP: {
+        struct kvm_s390_zpci_op args;
+
+        r = -EINVAL;
+        if (!IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM))
+            break;
+        if (copy_from_user(&args, argp, sizeof(args))) {
+            r = -EFAULT;
+            break;
+        }
+        r = kvm_s390_pci_zpci_op(kvm, &args);
+        if (r)
+            break;
+        if (copy_to_user(argp, &args, sizeof(args)))
+            r = -EFAULT;

So this copy_to_user() indicates that information is returned to userspace ... but below, the ioctl is declared with _IOW only ... this does not match. Should it be declared with _IOWR or should the copy_to_user() be dropped?

copy_to_user should be dropped.  Thanks!


+        break;
+    }
      default:
          r = -ENOTTY;
      }
diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index 1393a1604494..6e6254016be4 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -585,6 +585,87 @@ void kvm_s390_pci_clear_list(struct kvm *kvm)
      spin_unlock(&kvm->arch.kzdev_list_lock);
  }
+static struct zpci_dev *get_zdev_from_kvm_by_fh(struct kvm *kvm, u32 fh)
+{
+    struct zpci_dev *zdev = NULL;
+    struct kvm_zdev *kzdev;
+
+    spin_lock(&kvm->arch.kzdev_list_lock);
+    list_for_each_entry(kzdev, &kvm->arch.kzdev_list, entry) {
+        if (kzdev->zdev->fh == fh) {
+            zdev = kzdev->zdev;
+            break;
+        }
+    }
+    spin_unlock(&kvm->arch.kzdev_list_lock);
+
+    return zdev;
+}
+
+static int kvm_s390_pci_zpci_reg_aen(struct zpci_dev *zdev,
+                     struct kvm_s390_zpci_op *args)
+{
+    struct zpci_fib fib = {};
+
+    fib.fmt0.aibv = args->u.reg_aen.ibv;
+    fib.fmt0.isc = args->u.reg_aen.isc;
+    fib.fmt0.noi = args->u.reg_aen.noi;
+    if (args->u.reg_aen.sb != 0) {
+        fib.fmt0.aisb = args->u.reg_aen.sb;
+        fib.fmt0.aisbo = args->u.reg_aen.sbo;
+        fib.fmt0.sum = 1;
+    } else {
+        fib.fmt0.aisb = 0;
+        fib.fmt0.aisbo = 0;
+        fib.fmt0.sum = 0;
+    }
+
+    if (args->u.reg_aen.flags & KVM_S390_ZPCIOP_REGAEN_HOST)
+        return kvm_s390_pci_aif_enable(zdev, &fib, true);
+    else
+        return kvm_s390_pci_aif_enable(zdev, &fib, false);

Alternatively (just a matter of taste):

     bool hostflag;
     ...
     hostflag = (args->u.reg_aen.flags & KVM_S390_ZPCIOP_REGAEN_HOST);
     return kvm_s390_pci_aif_enable(zdev, &fib, hostflag);

+}
+
+int kvm_s390_pci_zpci_op(struct kvm *kvm, struct kvm_s390_zpci_op *args)
+{
+    struct kvm_zdev *kzdev;
+    struct zpci_dev *zdev;
+    int r;
+
+    zdev = get_zdev_from_kvm_by_fh(kvm, args->fh);
+    if (!zdev)
+        return -ENODEV;
+
+    mutex_lock(&zdev->kzdev_lock);
+    mutex_lock(&kvm->lock);
+
+    kzdev = zdev->kzdev;
+    if (!kzdev) {
+        r = -ENODEV;
+        goto out;
+    }
+    if (kzdev->kvm != kvm) {
+        r = -EPERM;
+        goto out;
+    }
+
+    switch (args->op) {
+    case KVM_S390_ZPCIOP_REG_AEN:

Please also check here that args->u.reg_aen.flags does not have any bits set that we don't support here (otherwise, this could cause some trouble when introducing additional flags later).

Good idea, will do


+        r = kvm_s390_pci_zpci_reg_aen(zdev, args);
+        break;
+    case KVM_S390_ZPCIOP_DEREG_AEN:
+        r = kvm_s390_pci_aif_disable(zdev, false);
+        break;
+    default:
+        r = -EINVAL;
+    }
+
+out:
+    mutex_unlock(&kvm->lock);
+    mutex_unlock(&zdev->kzdev_lock);
+    return r;
+}
+
  int kvm_s390_pci_init(void)
  {
      aift = kzalloc(sizeof(struct zpci_aift), GFP_KERNEL);
diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h
index fb2b91b76e0c..0351382e990f 100644
--- a/arch/s390/kvm/pci.h
+++ b/arch/s390/kvm/pci.h
@@ -59,6 +59,8 @@ void kvm_s390_pci_aen_exit(void);
  void kvm_s390_pci_init_list(struct kvm *kvm);
  void kvm_s390_pci_clear_list(struct kvm *kvm);
+int kvm_s390_pci_zpci_op(struct kvm *kvm, struct kvm_s390_zpci_op *args);
+
  int kvm_s390_pci_init(void);
  void kvm_s390_pci_exit(void);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6a184d260c7f..1d3d41523d10 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1152,6 +1152,7 @@ struct kvm_ppc_resize_hpt {
  #define KVM_CAP_DISABLE_QUIRKS2 213
  /* #define KVM_CAP_VM_TSC_CONTROL 214 */
  #define KVM_CAP_SYSTEM_EVENT_DATA 215
+#define KVM_CAP_S390_ZPCI_OP 216
  #ifdef KVM_CAP_IRQ_ROUTING
@@ -2068,4 +2069,34 @@ struct kvm_stats_desc {
  /* Available with KVM_CAP_XSAVE2 */
  #define KVM_GET_XSAVE2          _IOR(KVMIO,  0xcf, struct kvm_xsave)
+/* Available with KVM_CAP_S390_ZPCI_OP */
+#define KVM_S390_ZPCI_OP      _IOW(KVMIO,  0xd0, struct kvm_s390_zpci_op)

Please double-check whether this should be _IOWR instead (see above). >

As mentioned above, the copy_to_user() should be removed.

+struct kvm_s390_zpci_op {
+    /* in */
+    __u32 fh;        /* target device */
+    __u8  op;        /* operation to perform */
+    __u8  pad[3];
+    union {
+        /* for KVM_S390_ZPCIOP_REG_AEN */
+        struct {
+            __u64 ibv;    /* Guest addr of interrupt bit vector */
+            __u64 sb;    /* Guest addr of summary bit */
+            __u32 flags;
+            __u32 noi;    /* Number of interrupts */
+            __u8 isc;    /* Guest interrupt subclass */
+            __u8 sbo;    /* Offset of guest summary bit vector */
+            __u16 pad;
+        } reg_aen;
+        __u64 reserved[8];
+    } u;
+};
+
+/* types for kvm_s390_zpci_op->op */
+#define KVM_S390_ZPCIOP_REG_AEN        0
+#define KVM_S390_ZPCIOP_DEREG_AEN    1
+
+/* flags for kvm_s390_zpci_op->u.reg_aen.flags */
+#define KVM_S390_ZPCIOP_REGAEN_HOST    (1 << 0)
+
  #endif /* __LINUX_KVM_H */

  Thomas





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