[Xen-devel] [PATCH] xen: handle inbound migration of VMs without ioreq server pages

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

VMs created on older versions on Xen will not have been provisioned with
pages to support creation of non-default ioreq servers. In this case
the ioreq server API is not supported and QEMU's only option is to fall
back to using the default ioreq server pages as it did prior to
commit 3996e85c ("Xen: Use the ioreq-server API when available").

This patch therefore changes the code in xen_common.h to stop considering
a failure of xc_hvm_create_ioreq_server() as a hard failure but simply
as an indication that the guest is too old to support the ioreq server
API. Instead a boolean is set to cause reversion to old behaviour such
that the default ioreq server is then used.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
---
 include/hw/xen/xen_common.h | 123 +++++++++++++++++++++++++++++++-------------
 trace-events                |   1 +
 xen-hvm.c                   |   6 +--
 3 files changed, 90 insertions(+), 40 deletions(-)

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 640c31e..8707adc 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -107,6 +107,42 @@ static inline int xen_get_vmport_regs_pfn(xc_interface 
*xc, domid_t dom,
 
 #endif
 
+static inline int xen_get_default_ioreq_server_info(xc_interface *xc, domid_t 
dom,
+                                                    xen_pfn_t *ioreq_pfn,
+                                                    xen_pfn_t *bufioreq_pfn,
+                                                    evtchn_port_t 
*bufioreq_evtchn)
+{
+    unsigned long param;
+    int rc;
+
+    rc = xc_get_hvm_param(xc, dom, HVM_PARAM_IOREQ_PFN, &param);
+    if (rc < 0) {
+        fprintf(stderr, "failed to get HVM_PARAM_IOREQ_PFN\n");
+        return -1;
+    }
+
+    *ioreq_pfn = param;
+
+    rc = xc_get_hvm_param(xc, dom, HVM_PARAM_BUFIOREQ_PFN, &param);
+    if (rc < 0) {
+        fprintf(stderr, "failed to get HVM_PARAM_BUFIOREQ_PFN\n");
+        return -1;
+    }
+
+    *bufioreq_pfn = param;
+
+    rc = xc_get_hvm_param(xc, dom, HVM_PARAM_BUFIOREQ_EVTCHN,
+                          &param);
+    if (rc < 0) {
+        fprintf(stderr, "failed to get HVM_PARAM_BUFIOREQ_EVTCHN\n");
+        return -1;
+    }
+
+    *bufioreq_evtchn = param;
+
+    return 0;
+}
+
 /* Xen before 4.5 */
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 450
 
@@ -154,10 +190,9 @@ static inline void xen_unmap_pcidev(xc_interface *xc, 
domid_t dom,
 {
 }
 
-static inline int xen_create_ioreq_server(xc_interface *xc, domid_t dom,
-                                          ioservid_t *ioservid)
+static inline void xen_create_ioreq_server(xc_interface *xc, domid_t dom,
+                                           ioservid_t *ioservid)
 {
-    return 0;
 }
 
 static inline void xen_destroy_ioreq_server(xc_interface *xc, domid_t dom,
@@ -171,35 +206,8 @@ static inline int xen_get_ioreq_server_info(xc_interface 
*xc, domid_t dom,
                                             xen_pfn_t *bufioreq_pfn,
                                             evtchn_port_t *bufioreq_evtchn)
 {
-    unsigned long param;
-    int rc;
-
-    rc = xc_get_hvm_param(xc, dom, HVM_PARAM_IOREQ_PFN, &param);
-    if (rc < 0) {
-        fprintf(stderr, "failed to get HVM_PARAM_IOREQ_PFN\n");
-        return -1;
-    }
-
-    *ioreq_pfn = param;
-
-    rc = xc_get_hvm_param(xc, dom, HVM_PARAM_BUFIOREQ_PFN, &param);
-    if (rc < 0) {
-        fprintf(stderr, "failed to get HVM_PARAM_BUFIOREQ_PFN\n");
-        return -1;
-    }
-
-    *bufioreq_pfn = param;
-
-    rc = xc_get_hvm_param(xc, dom, HVM_PARAM_BUFIOREQ_EVTCHN,
-                          &param);
-    if (rc < 0) {
-        fprintf(stderr, "failed to get HVM_PARAM_BUFIOREQ_EVTCHN\n");
-        return -1;
-    }
-
-    *bufioreq_evtchn = param;
-
-    return 0;
+    return xen_get_default_ioreq_server_info(xc, dom, ioreq_pfn, bufioreq_pfn,
+                                             bufioreq_evtchn);
 }
 
 static inline int xen_set_ioreq_server_state(xc_interface *xc, domid_t dom,
@@ -212,6 +220,8 @@ static inline int xen_set_ioreq_server_state(xc_interface 
*xc, domid_t dom,
 /* Xen 4.5 */
 #else
 
+static bool use_default_ioreq_server;
+
 static inline void xen_map_memory_section(xc_interface *xc, domid_t dom,
                                           ioservid_t ioservid,
                                           MemoryRegionSection *section)
@@ -220,6 +230,10 @@ static inline void xen_map_memory_section(xc_interface 
*xc, domid_t dom,
     ram_addr_t size = int128_get64(section->size);
     hwaddr end_addr = start_addr + size - 1;
 
+    if (use_default_ioreq_server) {
+        return;
+    }
+
     trace_xen_map_mmio_range(ioservid, start_addr, end_addr);
     xc_hvm_map_io_range_to_ioreq_server(xc, dom, ioservid, 1,
                                         start_addr, end_addr);
@@ -233,6 +247,11 @@ static inline void xen_unmap_memory_section(xc_interface 
*xc, domid_t dom,
     ram_addr_t size = int128_get64(section->size);
     hwaddr end_addr = start_addr + size - 1;
 
+    if (use_default_ioreq_server) {
+        return;
+    }
+
+
     trace_xen_unmap_mmio_range(ioservid, start_addr, end_addr);
     xc_hvm_unmap_io_range_from_ioreq_server(xc, dom, ioservid, 1,
                                             start_addr, end_addr);
@@ -246,6 +265,11 @@ static inline void xen_map_io_section(xc_interface *xc, 
domid_t dom,
     ram_addr_t size = int128_get64(section->size);
     hwaddr end_addr = start_addr + size - 1;
 
+    if (use_default_ioreq_server) {
+        return;
+    }
+
+
     trace_xen_map_portio_range(ioservid, start_addr, end_addr);
     xc_hvm_map_io_range_to_ioreq_server(xc, dom, ioservid, 0,
                                         start_addr, end_addr);
@@ -259,6 +283,10 @@ static inline void xen_unmap_io_section(xc_interface *xc, 
domid_t dom,
     ram_addr_t size = int128_get64(section->size);
     hwaddr end_addr = start_addr + size - 1;
 
+    if (use_default_ioreq_server) {
+        return;
+    }
+
     trace_xen_unmap_portio_range(ioservid, start_addr, end_addr);
     xc_hvm_unmap_io_range_from_ioreq_server(xc, dom, ioservid, 0,
                                             start_addr, end_addr);
@@ -268,6 +296,10 @@ static inline void xen_map_pcidev(xc_interface *xc, 
domid_t dom,
                                   ioservid_t ioservid,
                                   PCIDevice *pci_dev)
 {
+    if (use_default_ioreq_server) {
+        return;
+    }
+
     trace_xen_map_pcidev(ioservid, pci_bus_num(pci_dev->bus),
                          PCI_SLOT(pci_dev->devfn), PCI_FUNC(pci_dev->devfn));
     xc_hvm_map_pcidev_to_ioreq_server(xc, dom, ioservid,
@@ -280,6 +312,10 @@ static inline void xen_unmap_pcidev(xc_interface *xc, 
domid_t dom,
                                     ioservid_t ioservid,
                                     PCIDevice *pci_dev)
 {
+    if (use_default_ioreq_server) {
+        return;
+    }
+
     trace_xen_unmap_pcidev(ioservid, pci_bus_num(pci_dev->bus),
                            PCI_SLOT(pci_dev->devfn), PCI_FUNC(pci_dev->devfn));
     xc_hvm_unmap_pcidev_from_ioreq_server(xc, dom, ioservid,
@@ -288,22 +324,29 @@ static inline void xen_unmap_pcidev(xc_interface *xc, 
domid_t dom,
                                           PCI_FUNC(pci_dev->devfn));
 }
 
-static inline int xen_create_ioreq_server(xc_interface *xc, domid_t dom,
-                                          ioservid_t *ioservid)
+static inline void xen_create_ioreq_server(xc_interface *xc, domid_t dom,
+                                           ioservid_t *ioservid)
 {
     int rc = xc_hvm_create_ioreq_server(xc, dom, HVM_IOREQSRV_BUFIOREQ_ATOMIC,
                                         ioservid);
 
     if (rc == 0) {
         trace_xen_ioreq_server_create(*ioservid);
+        return;
     }
 
-    return rc;
+    *ioservid = 0;
+    use_default_ioreq_server = true;
+    trace_xen_default_ioreq_server();
 }
 
 static inline void xen_destroy_ioreq_server(xc_interface *xc, domid_t dom,
                                             ioservid_t ioservid)
 {
+    if (use_default_ioreq_server) {
+        return;
+    }
+
     trace_xen_ioreq_server_destroy(ioservid);
     xc_hvm_destroy_ioreq_server(xc, dom, ioservid);
 }
@@ -314,6 +357,12 @@ static inline int xen_get_ioreq_server_info(xc_interface 
*xc, domid_t dom,
                                             xen_pfn_t *bufioreq_pfn,
                                             evtchn_port_t *bufioreq_evtchn)
 {
+    if (use_default_ioreq_server) {
+        return xen_get_default_ioreq_server_info(xc, dom, ioreq_pfn,
+                                                 bufioreq_pfn,
+                                                 bufioreq_evtchn);
+    }
+
     return xc_hvm_get_ioreq_server_info(xc, dom, ioservid,
                                         ioreq_pfn, bufioreq_pfn,
                                         bufioreq_evtchn);
@@ -323,6 +372,10 @@ static inline int xen_set_ioreq_server_state(xc_interface 
*xc, domid_t dom,
                                              ioservid_t ioservid,
                                              bool enable)
 {
+    if (use_default_ioreq_server) {
+        return 0;
+    }
+
     trace_xen_ioreq_server_state(ioservid, enable);
     return xc_hvm_set_ioreq_server_state(xc, dom, ioservid, enable);
 }
diff --git a/trace-events b/trace-events
index 52c6a6c..616cc52 100644
--- a/trace-events
+++ b/trace-events
@@ -60,6 +60,7 @@ spice_vmc_event(int event) "spice vmc event %d"
 # xen-hvm.c
 xen_ram_alloc(unsigned long ram_addr, unsigned long size) "requested: %#lx, 
size %#lx"
 xen_client_set_memory(uint64_t start_addr, unsigned long size, bool log_dirty) 
"%#"PRIx64" size %#lx, log_dirty %i"
+xen_default_ioreq_server(void) ""
 xen_ioreq_server_create(uint32_t id) "id: %u"
 xen_ioreq_server_destroy(uint32_t id) "id: %u"
 xen_ioreq_server_state(uint32_t id, bool enable) "id: %u: enable: %i"
diff --git a/xen-hvm.c b/xen-hvm.c
index eb57792..cc3d4b0 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -1203,11 +1203,7 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion 
**ram_memory)
         goto err;
     }
 
-    rc = xen_create_ioreq_server(xen_xc, xen_domid, &state->ioservid);
-    if (rc < 0) {
-        perror("xen: ioreq server create");
-        goto err;
-    }
+    xen_create_ioreq_server(xen_xc, xen_domid, &state->ioservid);
 
     state->exit.notify = xen_exit_notifier;
     qemu_add_exit_notifier(&state->exit);
-- 
2.1.4


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