pci: Convert msi_init() to Error and fix callers to check it

msi_init() reports errors with error_report(), which is wrong
when it's used in realize().

Fix by converting it to Error.

Fix its callers to handle failure instead of ignoring it.

For those callers who don't handle the failure, it might happen:
when user want msi on, but he doesn't get what he want because of
msi_init fails silently.

cc: Gerd Hoffmann <kraxel@redhat.com>
cc: John Snow <jsnow@redhat.com>
cc: Dmitry Fleytman <dmitry@daynix.com>
cc: Jason Wang <jasowang@redhat.com>
cc: Michael S. Tsirkin <mst@redhat.com>
cc: Hannes Reinecke <hare@suse.de>
cc: Paolo Bonzini <pbonzini@redhat.com>
cc: Alex Williamson <alex.williamson@redhat.com>
cc: Markus Armbruster <armbru@redhat.com>
cc: Marcel Apfelbaum <marcel@redhat.com>

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>

14 files changed, 148 insertions, 66 deletions

diff --git a/hw/audio/intel-hda.c b/hw/audio/intel-hda.c
index 4e19e8b0f2..cd95340cd9 100644
--- a/hw/audio/intel-hda.c
+++ b/hw/audio/intel-hda.c
@@ -1132,6 +1132,8 @@ static void intel_hda_realize(PCIDevice *pci, Error **errp)
 {
     IntelHDAState *d = INTEL_HDA(pci);
     uint8_t *conf = d->pci.config;
+    Error *err = NULL;
+    int ret;
 
     d->name = object_get_typename(OBJECT(d));
 
@@ -1140,13 +1142,27 @@ static void intel_hda_realize(PCIDevice *pci, Error **errp)
     /* HDCTL off 0x40 bit 0 selects signaling mode (1-HDA, 0 - Ac97) 18.1.19 */
     conf[0x40] = 0x01;
 
+    if (d->msi != ON_OFF_AUTO_OFF) {
+        ret = msi_init(&d->pci, d->old_msi_addr ? 0x50 : 0x60,
+                       1, true, false, &err);
+        /* Any error other than -ENOTSUP(board's MSI support is broken)
+         * is a programming error */
+        assert(!ret || ret == -ENOTSUP);
+        if (ret && d->msi == ON_OFF_AUTO_ON) {
+            /* Can't satisfy user's explicit msi=on request, fail */
+            error_append_hint(&err, "You have to use msi=auto (default) or "
+                    "msi=off with this machine type.\n");
+            error_propagate(errp, err);
+            return;
+        }
+        assert(!err || d->msi == ON_OFF_AUTO_AUTO);
+        /* With msi=auto, we fall back to MSI off silently */
+        error_free(err);
+    }
+
     memory_region_init_io(&d->mmio, OBJECT(d), &intel_hda_mmio_ops, d,
                           "intel-hda", 0x4000);
     pci_register_bar(&d->pci, 0, 0, &d->mmio);
-    if (d->msi != ON_OFF_AUTO_OFF) {
-         /* TODO check for errors */
-        msi_init(&d->pci, d->old_msi_addr ? 0x50 : 0x60, 1, true, false);
-    }
 
     hda_codec_bus_init(DEVICE(pci), &d->codecs, sizeof(d->codecs),
                        intel_hda_response, intel_hda_xfer);
diff --git a/hw/ide/ich.c b/hw/ide/ich.c
index 0a13334baa..920ec276ed 100644
--- a/hw/ide/ich.c
+++ b/hw/ide/ich.c
@@ -68,7 +68,6 @@
 #include <hw/isa/isa.h>
 #include "sysemu/block-backend.h"
 #include "sysemu/dma.h"
-
 #include <hw/ide/pci.h>
 #include <hw/ide/ahci.h>
 
@@ -111,6 +110,7 @@ static void pci_ich9_ahci_realize(PCIDevice *dev, Error **errp)
     int sata_cap_offset;
     uint8_t *sata_cap;
     d = ICH_AHCI(dev);
+    int ret;
 
     ahci_realize(&d->ahci, DEVICE(dev), pci_get_address_space(dev), 6);
 
@@ -146,7 +146,10 @@ static void pci_ich9_ahci_realize(PCIDevice *dev, Error **errp)
     /* Although the AHCI 1.3 specification states that the first capability
      * should be PMCAP, the Intel ICH9 data sheet specifies that the ICH9
      * AHCI device puts the MSI capability first, pointing to 0x80. */
-    msi_init(dev, ICH9_MSI_CAP_OFFSET, 1, true, false);
+    ret = msi_init(dev, ICH9_MSI_CAP_OFFSET, 1, true, false, NULL);
+    /* Any error other than -ENOTSUP(board's MSI support is broken)
+     * is a programming error.  Fall back to INTx silently on -ENOTSUP */
+    assert(!ret || ret == -ENOTSUP);
 }
 
 static void pci_ich9_uninit(PCIDevice *dev)
diff --git a/hw/net/e1000e.c b/hw/net/e1000e.c
index 692283fdd7..a06d1848d2 100644
--- a/hw/net/e1000e.c
+++ b/hw/net/e1000e.c
@@ -268,13 +268,9 @@ e1000e_init_msi(E1000EState *s)
 {
     int res;
 
-    res = msi_init(PCI_DEVICE(s),
-                   0xD0,   /* MSI capability offset              */
-                   1,      /* MAC MSI interrupts                 */
-                   true,   /* 64-bit message addresses supported */
-                   false); /* Per vector mask supported          */
+    res = msi_init(PCI_DEVICE(s), 0xD0, 1, true, false, NULL);
 
-    if (res > 0) {
+    if (!res) {
         s->intr_state |= E1000E_USE_MSI;
     } else {
         trace_e1000e_msi_init_fail(res);
diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
index 92236d3919..f24298cc49 100644
--- a/hw/net/vmxnet3.c
+++ b/hw/net/vmxnet3.c
@@ -2216,27 +2216,6 @@ vmxnet3_cleanup_msix(VMXNET3State *s)
     }
 }
 
-#define VMXNET3_USE_64BIT         (true)
-#define VMXNET3_PER_VECTOR_MASK   (false)
-
-static bool
-vmxnet3_init_msi(VMXNET3State *s)
-{
-    PCIDevice *d = PCI_DEVICE(s);
-    int res;
-
-    res = msi_init(d, VMXNET3_MSI_OFFSET(s), VMXNET3_MAX_NMSIX_INTRS,
-                   VMXNET3_USE_64BIT, VMXNET3_PER_VECTOR_MASK);
-    if (0 > res) {
-        VMW_WRPRN("Failed to initialize MSI, error %d", res);
-        s->msi_used = false;
-    } else {
-        s->msi_used = true;
-    }
-
-    return s->msi_used;
-}
-
 static void
 vmxnet3_cleanup_msi(VMXNET3State *s)
 {
@@ -2298,10 +2277,15 @@ static uint64_t vmxnet3_device_serial_num(VMXNET3State *s)
     return dsn_payload;
 }
 
+
+#define VMXNET3_USE_64BIT         (true)
+#define VMXNET3_PER_VECTOR_MASK   (false)
+
 static void vmxnet3_pci_realize(PCIDevice *pci_dev, Error **errp)
 {
     DeviceState *dev = DEVICE(pci_dev);
     VMXNET3State *s = VMXNET3(pci_dev);
+    int ret;
 
     VMW_CBPRN("Starting init...");
 
@@ -2325,14 +2309,17 @@ static void vmxnet3_pci_realize(PCIDevice *pci_dev, Error **errp)
     /* Interrupt pin A */
     pci_dev->config[PCI_INTERRUPT_PIN] = 0x01;
 
+    ret = msi_init(pci_dev, VMXNET3_MSI_OFFSET(s), VMXNET3_MAX_NMSIX_INTRS,
+                   VMXNET3_USE_64BIT, VMXNET3_PER_VECTOR_MASK, NULL);
+    /* Any error other than -ENOTSUP(board's MSI support is broken)
+     * is a programming error. Fall back to INTx silently on -ENOTSUP */
+    assert(!ret || ret == -ENOTSUP);
+    s->msi_used = !ret;
+
     if (!vmxnet3_init_msix(s)) {
         VMW_WRPRN("Failed to initialize MSI-X, configuration is inconsistent.");
     }
 
-    if (!vmxnet3_init_msi(s)) {
-        VMW_WRPRN("Failed to initialize MSI, configuration is inconsistent.");
-    }
-
     vmxnet3_net_init(s);
 
     if (pci_is_express(pci_dev)) {
diff --git a/hw/pci-bridge/ioh3420.c b/hw/pci-bridge/ioh3420.c
index b4a7806e2e..93c6f0b7a2 100644
--- a/hw/pci-bridge/ioh3420.c
+++ b/hw/pci-bridge/ioh3420.c
@@ -25,6 +25,7 @@
 #include "hw/pci/msi.h"
 #include "hw/pci/pcie.h"
 #include "ioh3420.h"
+#include "qapi/error.h"
 
 #define PCI_DEVICE_ID_IOH_EPORT         0x3420  /* D0:F0 express mode */
 #define PCI_DEVICE_ID_IOH_REV           0x2
@@ -97,6 +98,7 @@ static int ioh3420_initfn(PCIDevice *d)
     PCIEPort *p = PCIE_PORT(d);
     PCIESlot *s = PCIE_SLOT(d);
     int rc;
+    Error *err = NULL;
 
     pci_bridge_initfn(d, TYPE_PCIE_BUS);
     pcie_port_init_reg(d);
@@ -109,8 +111,10 @@ static int ioh3420_initfn(PCIDevice *d)
 
     rc = msi_init(d, IOH_EP_MSI_OFFSET, IOH_EP_MSI_NR_VECTOR,
                   IOH_EP_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_64BIT,
-                  IOH_EP_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT);
+                  IOH_EP_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT, &err);
     if (rc < 0) {
+        assert(rc == -ENOTSUP);
+        error_report_err(err);
         goto err_bridge;
     }
 
diff --git a/hw/pci-bridge/pci_bridge_dev.c b/hw/pci-bridge/pci_bridge_dev.c
index 0fbecc4bbd..5dbd933cc1 100644
--- a/hw/pci-bridge/pci_bridge_dev.c
+++ b/hw/pci-bridge/pci_bridge_dev.c
@@ -54,6 +54,7 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
     PCIBridge *br = PCI_BRIDGE(dev);
     PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(dev);
     int err;
+    Error *local_err = NULL;
 
     pci_bridge_initfn(dev, TYPE_PCI_BUS);
 
@@ -75,12 +76,23 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
         goto slotid_error;
     }
 
-    if (bridge_dev->msi != ON_OFF_AUTO_OFF &&
-        msi_nonbroken) {
-        err = msi_init(dev, 0, 1, true, true);
-        if (err < 0) {
+    if (bridge_dev->msi != ON_OFF_AUTO_OFF) {
+        /* it means SHPC exists, because MSI is needed by SHPC */
+
+        err = msi_init(dev, 0, 1, true, true, &local_err);
+        /* Any error other than -ENOTSUP(board's MSI support is broken)
+         * is a programming error */
+        assert(!err || err == -ENOTSUP);
+        if (err && bridge_dev->msi == ON_OFF_AUTO_ON) {
+            /* Can't satisfy user's explicit msi=on request, fail */
+            error_append_hint(&local_err, "You have to use msi=auto (default) "
+                    "or msi=off with this machine type.\n");
+            error_report_err(local_err);
             goto msi_error;
         }
+        assert(!local_err || bridge_dev->msi == ON_OFF_AUTO_AUTO);
+        /* With msi=auto, we fall back to MSI off silently */
+        error_free(local_err);
     }
 
     if (shpc_present(dev)) {
diff --git a/hw/pci-bridge/xio3130_downstream.c b/hw/pci-bridge/xio3130_downstream.c
index e6d653de4f..f6149a302d 100644
--- a/hw/pci-bridge/xio3130_downstream.c
+++ b/hw/pci-bridge/xio3130_downstream.c
@@ -24,6 +24,7 @@
 #include "hw/pci/msi.h"
 #include "hw/pci/pcie.h"
 #include "xio3130_downstream.h"
+#include "qapi/error.h"
 
 #define PCI_DEVICE_ID_TI_XIO3130D       0x8233  /* downstream port */
 #define XIO3130_REVISION                0x1
@@ -60,14 +61,17 @@ static int xio3130_downstream_initfn(PCIDevice *d)
     PCIEPort *p = PCIE_PORT(d);
     PCIESlot *s = PCIE_SLOT(d);
     int rc;
+    Error *err = NULL;
 
     pci_bridge_initfn(d, TYPE_PCIE_BUS);
     pcie_port_init_reg(d);
 
     rc = msi_init(d, XIO3130_MSI_OFFSET, XIO3130_MSI_NR_VECTOR,
                   XIO3130_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_64BIT,
-                  XIO3130_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT);
+                  XIO3130_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT, &err);
     if (rc < 0) {
+        assert(rc == -ENOTSUP);
+        error_report_err(err);
         goto err_bridge;
     }
 
diff --git a/hw/pci-bridge/xio3130_upstream.c b/hw/pci-bridge/xio3130_upstream.c
index d97684474f..487edacc1d 100644
--- a/hw/pci-bridge/xio3130_upstream.c
+++ b/hw/pci-bridge/xio3130_upstream.c
@@ -24,6 +24,7 @@
 #include "hw/pci/msi.h"
 #include "hw/pci/pcie.h"
 #include "xio3130_upstream.h"
+#include "qapi/error.h"
 
 #define PCI_DEVICE_ID_TI_XIO3130U       0x8232  /* upstream port */
 #define XIO3130_REVISION                0x2
@@ -56,14 +57,17 @@ static int xio3130_upstream_initfn(PCIDevice *d)
 {
     PCIEPort *p = PCIE_PORT(d);
     int rc;
+    Error *err = NULL;
 
     pci_bridge_initfn(d, TYPE_PCIE_BUS);
     pcie_port_init_reg(d);
 
     rc = msi_init(d, XIO3130_MSI_OFFSET, XIO3130_MSI_NR_VECTOR,
                   XIO3130_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_64BIT,
-                  XIO3130_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT);
+                  XIO3130_MSI_SUPPORTED_FLAGS & PCI_MSI_FLAGS_MASKBIT, &err);
     if (rc < 0) {
+        assert(rc == -ENOTSUP);
+        error_report_err(err);
         goto err_bridge;
     }
 
diff --git a/hw/pci/msi.c b/hw/pci/msi.c
index ed792251dd..a87b2278a3 100644
--- a/hw/pci/msi.c
+++ b/hw/pci/msi.c
@@ -22,6 +22,7 @@
 #include "hw/pci/msi.h"
 #include "hw/xen/xen.h"
 #include "qemu/range.h"
+#include "qapi/error.h"
 
 /* PCI_MSI_ADDRESS_LO */
 #define PCI_MSI_ADDRESS_LO_MASK         (~0x3)
@@ -173,7 +174,8 @@ bool msi_enabled(const PCIDevice *dev)
  * If @msi64bit, make the device capable of sending a 64-bit message
  * address.
  * If @msi_per_vector_mask, make the device support per-vector masking.
- * Return 0 on success, return -errno on error.
+ * @errp is for returning errors.
+ * Return 0 on success; set @errp and return -errno on error.
  *
  * -ENOTSUP means lacking msi support for a msi-capable platform.
  * -EINVAL means capability overlap, happens when @offset is non-zero,
@@ -181,7 +183,8 @@ bool msi_enabled(const PCIDevice *dev)
  *  if a real HW is broken.
  */
 int msi_init(struct PCIDevice *dev, uint8_t offset,
-             unsigned int nr_vectors, bool msi64bit, bool msi_per_vector_mask)
+             unsigned int nr_vectors, bool msi64bit,
+             bool msi_per_vector_mask, Error **errp)
 {
     unsigned int vectors_order;
     uint16_t flags;
@@ -189,6 +192,7 @@ int msi_init(struct PCIDevice *dev, uint8_t offset,
     int config_offset;
 
     if (!msi_nonbroken) {
+        error_setg(errp, "MSI is not supported by interrupt controller");
         return -ENOTSUP;
     }
 
@@ -212,7 +216,8 @@ int msi_init(struct PCIDevice *dev, uint8_t offset,
     }
 
     cap_size = msi_cap_sizeof(flags);
-    config_offset = pci_add_capability(dev, PCI_CAP_ID_MSI, offset, cap_size);
+    config_offset = pci_add_capability2(dev, PCI_CAP_ID_MSI, offset,
+                                        cap_size, errp);
     if (config_offset < 0) {
         return config_offset;
     }
diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
index 636ea73adb..6eb57ff61b 100644
--- a/hw/scsi/megasas.c
+++ b/hw/scsi/megasas.c
@@ -29,7 +29,7 @@
 #include "hw/scsi/scsi.h"
 #include "block/scsi.h"
 #include "trace.h"
-
+#include "qapi/error.h"
 #include "mfi.h"
 
 #define MEGASAS_VERSION_GEN1 "1.70"
@@ -2330,6 +2330,8 @@ static void megasas_scsi_realize(PCIDevice *dev, Error **errp)
     MegasasBaseClass *b = MEGASAS_DEVICE_GET_CLASS(s);
     uint8_t *pci_conf;
     int i, bar_type;
+    Error *err = NULL;
+    int ret;
 
     pci_conf = dev->config;
 
@@ -2338,6 +2340,24 @@ static void megasas_scsi_realize(PCIDevice *dev, Error **errp)
     /* Interrupt pin 1 */
     pci_conf[PCI_INTERRUPT_PIN] = 0x01;
 
+    if (megasas_use_msi(s)) {
+        ret = msi_init(dev, 0x50, 1, true, false, &err);
+        /* Any error other than -ENOTSUP(board's MSI support is broken)
+         * is a programming error */
+        assert(!ret || ret == -ENOTSUP);
+        if (ret && s->msi == ON_OFF_AUTO_ON) {
+            /* Can't satisfy user's explicit msi=on request, fail */
+            error_append_hint(&err, "You have to use msi=auto (default) or "
+                    "msi=off with this machine type.\n");
+            error_propagate(errp, err);
+            return;
+        } else if (ret) {
+            /* With msi=auto, we fall back to MSI off silently */
+            s->msi = ON_OFF_AUTO_OFF;
+            error_free(err);
+        }
+    }
+
     memory_region_init_io(&s->mmio_io, OBJECT(s), &megasas_mmio_ops, s,
                           "megasas-mmio", 0x4000);
     memory_region_init_io(&s->port_io, OBJECT(s), &megasas_port_ops, s,
@@ -2345,10 +2365,6 @@ static void megasas_scsi_realize(PCIDevice *dev, Error **errp)
     memory_region_init_io(&s->queue_io, OBJECT(s), &megasas_queue_ops, s,
                           "megasas-queue", 0x40000);
 
-    if (megasas_use_msi(s) &&
-        msi_init(dev, 0x50, 1, true, false)) {
-        s->msi = ON_OFF_AUTO_OFF;
-    }
     if (megasas_use_msix(s) &&
         msix_init(dev, 15, &s->mmio_io, b->mmio_bar, 0x2000,
                   &s->mmio_io, b->mmio_bar, 0x3800, 0x68)) {
diff --git a/hw/scsi/mptsas.c b/hw/scsi/mptsas.c
index 40033c4399..bb056c4e41 100644
--- a/hw/scsi/mptsas.c
+++ b/hw/scsi/mptsas.c
@@ -32,7 +32,7 @@
 #include "hw/scsi/scsi.h"
 #include "block/scsi.h"
 #include "trace.h"
-
+#include "qapi/error.h"
 #include "mptsas.h"
 #include "mpi.h"
 
@@ -1273,10 +1273,33 @@ static void mptsas_scsi_init(PCIDevice *dev, Error **errp)
 {
     DeviceState *d = DEVICE(dev);
     MPTSASState *s = MPT_SAS(dev);
+    Error *err = NULL;
+    int ret;
 
     dev->config[PCI_LATENCY_TIMER] = 0;
     dev->config[PCI_INTERRUPT_PIN] = 0x01;
 
+    if (s->msi != ON_OFF_AUTO_OFF) {
+        ret = msi_init(dev, 0, 1, true, false, &err);
+        /* Any error other than -ENOTSUP(board's MSI support is broken)
+         * is a programming error */
+        assert(!ret || ret == -ENOTSUP);
+        if (ret && s->msi == ON_OFF_AUTO_ON) {
+            /* Can't satisfy user's explicit msi=on request, fail */
+            error_append_hint(&err, "You have to use msi=auto (default) or "
+                    "msi=off with this machine type.\n");
+            error_propagate(errp, err);
+            s->msi_in_use = false;
+            return;
+        } else if (ret) {
+            /* With msi=auto, we fall back to MSI off silently */
+            error_free(err);
+            s->msi_in_use = false;
+        } else {
+            s->msi_in_use = true;
+        }
+    }
+
     memory_region_init_io(&s->mmio_io, OBJECT(s), &mptsas_mmio_ops, s,
                           "mptsas-mmio", 0x4000);
     memory_region_init_io(&s->port_io, OBJECT(s), &mptsas_port_ops, s,
@@ -1284,12 +1307,6 @@ static void mptsas_scsi_init(PCIDevice *dev, Error **errp)
     memory_region_init_io(&s->diag_io, OBJECT(s), &mptsas_diag_ops, s,
                           "mptsas-diag", 0x10000);
 
-    if (s->msi != ON_OFF_AUTO_OFF &&
-        msi_init(dev, 0, 1, true, false) >= 0) {
-        /* TODO check for errors */
-        s->msi_in_use = true;
-    }
-
     pci_register_bar(dev, 0, PCI_BASE_ADDRESS_SPACE_IO, &s->port_io);
     pci_register_bar(dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY |
                                  PCI_BASE_ADDRESS_MEM_TYPE_32, &s->mmio_io);
diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c
index e035fcea34..ecd6077f4b 100644
--- a/hw/scsi/vmw_pvscsi.c
+++ b/hw/scsi/vmw_pvscsi.c
@@ -1063,7 +1063,7 @@ pvscsi_init_msi(PVSCSIState *s)
     PCIDevice *d = PCI_DEVICE(s);
 
     res = msi_init(d, PVSCSI_MSI_OFFSET(s), PVSCSI_MSIX_NUM_VECTORS,
-                   PVSCSI_USE_64BIT, PVSCSI_PER_VECTOR_MASK);
+                   PVSCSI_USE_64BIT, PVSCSI_PER_VECTOR_MASK, NULL);
     if (res < 0) {
         trace_pvscsi_init_msi_fail(res);
         s->msi_used = false;
diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index 0a5510fbc2..1a3377f038 100644
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -26,6 +26,7 @@
 #include "hw/pci/msi.h"
 #include "hw/pci/msix.h"
 #include "trace.h"
+#include "qapi/error.h"
 
 //#define DEBUG_XHCI
 //#define DEBUG_DATA
@@ -3581,6 +3582,7 @@ static void usb_xhci_init(XHCIState *xhci)
 static void usb_xhci_realize(struct PCIDevice *dev, Error **errp)
 {
     int i, ret;
+    Error *err = NULL;
 
     XHCIState *xhci = XHCI(dev);
 
@@ -3591,6 +3593,23 @@ static void usb_xhci_realize(struct PCIDevice *dev, Error **errp)
 
     usb_xhci_init(xhci);
 
+    if (xhci->msi != ON_OFF_AUTO_OFF) {
+        ret = msi_init(dev, 0x70, xhci->numintrs, true, false, &err);
+        /* Any error other than -ENOTSUP(board's MSI support is broken)
+         * is a programming error */
+        assert(!ret || ret == -ENOTSUP);
+        if (ret && xhci->msi == ON_OFF_AUTO_ON) {
+            /* Can't satisfy user's explicit msi=on request, fail */
+            error_append_hint(&err, "You have to use msi=auto (default) or "
+                    "msi=off with this machine type.\n");
+            error_propagate(errp, err);
+            return;
+        }
+        assert(!err || xhci->msi == ON_OFF_AUTO_AUTO);
+        /* With msi=auto, we fall back to MSI off silently */
+        error_free(err);
+    }
+
     if (xhci->numintrs > MAXINTRS) {
         xhci->numintrs = MAXINTRS;
     }
@@ -3648,10 +3667,6 @@ static void usb_xhci_realize(struct PCIDevice *dev, Error **errp)
         assert(ret >= 0);
     }
 
-    if (xhci->msi != ON_OFF_AUTO_OFF) {
-        /* TODO check for errors */
-        msi_init(dev, 0x70, xhci->numintrs, true, false);
-    }
     if (xhci->msix != ON_OFF_AUTO_OFF) {
         /* TODO check for errors */
         msix_init(dev, xhci->numintrs,
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index f2c679e47c..44783c50ab 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -31,6 +31,7 @@
 #include "sysemu/sysemu.h"
 #include "pci.h"
 #include "trace.h"
+#include "qapi/error.h"
 
 #define MSIX_CAP_LENGTH 12
 
@@ -1170,6 +1171,7 @@ static int vfio_msi_setup(VFIOPCIDevice *vdev, int pos)
     uint16_t ctrl;
     bool msi_64bit, msi_maskbit;
     int ret, entries;
+    Error *err = NULL;
 
     if (pread(vdev->vbasedev.fd, &ctrl, sizeof(ctrl),
               vdev->config_offset + pos + PCI_CAP_FLAGS) != sizeof(ctrl)) {
@@ -1183,12 +1185,13 @@ static int vfio_msi_setup(VFIOPCIDevice *vdev, int pos)
 
     trace_vfio_msi_setup(vdev->vbasedev.name, pos);
 
-    ret = msi_init(&vdev->pdev, pos, entries, msi_64bit, msi_maskbit);
+    ret = msi_init(&vdev->pdev, pos, entries, msi_64bit, msi_maskbit, &err);
     if (ret < 0) {
         if (ret == -ENOTSUP) {
             return 0;
         }
-        error_report("vfio: msi_init failed");
+        error_prepend(&err, "vfio: msi_init failed: ");
+        error_report_err(err);
         return ret;
     }
     vdev->msi_cap_size = 0xa + (msi_maskbit ? 0xa : 0) + (msi_64bit ? 0x4 : 0);