s390x/pci: add routine to get host function handle from CLP info

In order to interface with the underlying host zPCI device, we need
to know its function handle. Add a routine to grab this from the
vfio CLP capabilities chain.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20220902172737.170349-3-mjrosato@linux.ibm.com>
[thuth: Replace free(info) with g_free(info)]
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/s390x/s390-pci-vfio.c

@@ -124,6 +124,27 @@ static void s390_pci_read_base(S390PCIBusDevice *pbdev,
     pbdev->zpci_fn.pft = 0;
 }
 
+static bool get_host_fh(S390PCIBusDevice *pbdev, struct vfio_device_info *info,
+                        uint32_t *fh)
+{
+    struct vfio_info_cap_header *hdr;
+    struct vfio_device_info_cap_zpci_base *cap;
+    VFIOPCIDevice *vpci = container_of(pbdev->pdev, VFIOPCIDevice, pdev);
+
+    hdr = vfio_get_device_info_cap(info, VFIO_DEVICE_INFO_CAP_ZPCI_BASE);
+
+    /* Can only get the host fh with version 2 or greater */
+    if (hdr == NULL || hdr->version < 2) {
+        trace_s390_pci_clp_cap(vpci->vbasedev.name,
+                               VFIO_DEVICE_INFO_CAP_ZPCI_BASE);
+        return false;
+    }
+    cap = (void *) hdr;
+
+    *fh = cap->fh;
+    return true;
+}
+
 static void s390_pci_read_group(S390PCIBusDevice *pbdev,
                                 struct vfio_device_info *info)
 {
@@ -217,25 +238,13 @@ static void s390_pci_read_pfip(S390PCIBusDevice *pbdev,
     memcpy(pbdev->zpci_fn.pfip, cap->pfip, CLP_PFIP_NR_SEGMENTS);
 }
 
-/*
- * This function will issue the VFIO_DEVICE_GET_INFO ioctl and look for
- * capabilities that contain information about CLP features provided by the
- * underlying host.
- * On entry, defaults have already been placed into the guest CLP response
- * buffers.  On exit, defaults will have been overwritten for any CLP features
- * found in the capability chain; defaults will remain for any CLP features not
- * found in the chain.
- */
-void s390_pci_get_clp_info(S390PCIBusDevice *pbdev)
+static struct vfio_device_info *get_device_info(S390PCIBusDevice *pbdev,
+                                                uint32_t argsz)
 {
-    g_autofree struct vfio_device_info *info = NULL;
+    struct vfio_device_info *info = g_malloc0(argsz);
     VFIOPCIDevice *vfio_pci;
-    uint32_t argsz;
     int fd;
 
-    argsz = sizeof(*info);
-    info = g_malloc0(argsz);
-
     vfio_pci = container_of(pbdev->pdev, VFIOPCIDevice, pdev);
     fd = vfio_pci->vbasedev.fd;
 
@@ -250,7 +259,8 @@ retry:
 
     if (ioctl(fd, VFIO_DEVICE_GET_INFO, info)) {
         trace_s390_pci_clp_dev_info(vfio_pci->vbasedev.name);
-        return;
+        g_free(info);
+        return NULL;
     }
 
     if (info->argsz > argsz) {
@@ -259,6 +269,47 @@ retry:
         goto retry;
     }
 
+    return info;
+}
+
+/*
+ * Get the host function handle from the vfio CLP capabilities chain.  Returns
+ * true if a fh value was placed into the provided buffer.  Returns false
+ * if a fh could not be obtained (ioctl failed or capabilitiy version does
+ * not include the fh)
+ */
+bool s390_pci_get_host_fh(S390PCIBusDevice *pbdev, uint32_t *fh)
+{
+    g_autofree struct vfio_device_info *info = NULL;
+
+    assert(fh);
+
+    info = get_device_info(pbdev, sizeof(*info));
+    if (!info) {
+        return false;
+    }
+
+    return get_host_fh(pbdev, info, fh);
+}
+
+/*
+ * This function will issue the VFIO_DEVICE_GET_INFO ioctl and look for
+ * capabilities that contain information about CLP features provided by the
+ * underlying host.
+ * On entry, defaults have already been placed into the guest CLP response
+ * buffers.  On exit, defaults will have been overwritten for any CLP features
+ * found in the capability chain; defaults will remain for any CLP features not
+ * found in the chain.
+ */
+void s390_pci_get_clp_info(S390PCIBusDevice *pbdev)
+{
+    g_autofree struct vfio_device_info *info = NULL;
+
+    info = get_device_info(pbdev, sizeof(*info));
+    if (!info) {
+        return;
+    }
+
     /*
      * Find the CLP features provided and fill in the guest CLP responses.
      * Always call s390_pci_read_base first as information from this could

include/hw/s390x/s390-pci-vfio.h

@@ -20,6 +20,7 @@ bool s390_pci_update_dma_avail(int fd, unsigned int *avail);
 S390PCIDMACount *s390_pci_start_dma_count(S390pciState *s,
                                           S390PCIBusDevice *pbdev);
 void s390_pci_end_dma_count(S390pciState *s, S390PCIDMACount *cnt);
+bool s390_pci_get_host_fh(S390PCIBusDevice *pbdev, uint32_t *fh);
 void s390_pci_get_clp_info(S390PCIBusDevice *pbdev);
 #else
 static inline bool s390_pci_update_dma_avail(int fd, unsigned int *avail)
@@ -33,6 +34,10 @@ static inline S390PCIDMACount *s390_pci_start_dma_count(S390pciState *s,
 }
 static inline void s390_pci_end_dma_count(S390pciState *s,
                                           S390PCIDMACount *cnt) { }
+static inline bool s390_pci_get_host_fh(S390PCIBusDevice *pbdev, uint32_t *fh)
+{
+    return false;
+}
 static inline void s390_pci_get_clp_info(S390PCIBusDevice *pbdev) { }
 #endif