Merge branch 'xenfv-kvm-15' of git://git.infradead.org/users/dwmw2/qemu into HEAD

This adds support for emulating Xen under Linux/KVM, based on kernel
patches which have been present since Linux v5.12. As with the kernel
support, it's derived from work started by João Martins of Oracle in
2018.

This series just adds the basic platform support — CPUID, hypercalls,
event channels, a stub of XenStore.

A full single-tenant internal implementation of XenStore, and patches
to make QEMU's Xen PV drivers work with this Xen emulation, are waiting
in the wings to be submitted in a follow-on patch series.

As noted in the documentation, it's enabled by setting the xen-version
property on the KVM accelerator, e.g.:

 qemu-system-x86_64 -serial mon:stdio -M q35 -display none -m 1G -smp 2 \
    -accel kvm,xen-version=0x4000e,kernel-irqchip=split \
    -kernel vmlinuz-6.0.7-301.fc37.x86_64 \
    -append "console=ttyS0 root=/dev/sda1" \
    -drive file=/var/lib/libvirt/images/fedora28.qcow2,if=none,id=disk \
    -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.0

Even before this was merged, we've already been using it to find and fix
bugs in the Linux kernel Xen guest support:

https://lore.kernel.org/all/4bffa69a949bfdc92c4a18e5a1c3cbb3b94a0d32.camel@infradead.org/
https://lore.kernel.org/all/871qnunycr.ffs@tglx/

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 41 insertions, 17 deletions

diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
index 66e6de31a6..539f7da374 100644
--- a/hw/i386/xen/xen_platform.c
+++ b/hw/i386/xen/xen_platform.c
@@ -25,12 +25,11 @@
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
-#include "hw/ide.h"
 #include "hw/ide/pci.h"
 #include "hw/pci/pci.h"
-#include "hw/xen/xen_common.h"
 #include "migration/vmstate.h"
-#include "hw/xen/xen-legacy-backend.h"
+#include "hw/xen/xen.h"
+#include "net/net.h"
 #include "trace.h"
 #include "sysemu/xen.h"
 #include "sysemu/block-backend.h"
@@ -38,6 +37,11 @@
 #include "qemu/module.h"
 #include "qom/object.h"
 
+#ifdef CONFIG_XEN
+#include "hw/xen/xen_common.h"
+#include "hw/xen/xen-legacy-backend.h"
+#endif
+
 //#define DEBUG_PLATFORM
 
 #ifdef DEBUG_PLATFORM
@@ -109,12 +113,25 @@ static void log_writeb(PCIXenPlatformState *s, char val)
 #define _UNPLUG_NVME_DISKS 3
 #define UNPLUG_NVME_DISKS (1u << _UNPLUG_NVME_DISKS)
 
+static bool pci_device_is_passthrough(PCIDevice *d)
+{
+    if (!strcmp(d->name, "xen-pci-passthrough")) {
+        return true;
+    }
+
+    if (xen_mode == XEN_EMULATE && !strcmp(d->name, "vfio-pci")) {
+        return true;
+    }
+
+    return false;
+}
+
 static void unplug_nic(PCIBus *b, PCIDevice *d, void *o)
 {
     /* We have to ignore passthrough devices */
     if (pci_get_word(d->config + PCI_CLASS_DEVICE) ==
             PCI_CLASS_NETWORK_ETHERNET
-            && strcmp(d->name, "xen-pci-passthrough") != 0) {
+            && !pci_device_is_passthrough(d)) {
         object_unparent(OBJECT(d));
     }
 }
@@ -187,9 +204,8 @@ static void unplug_disks(PCIBus *b, PCIDevice *d, void *opaque)
         !(flags & UNPLUG_IDE_SCSI_DISKS);
 
     /* We have to ignore passthrough devices */
-    if (!strcmp(d->name, "xen-pci-passthrough")) {
+    if (pci_device_is_passthrough(d))
         return;
-    }
 
     switch (pci_get_word(d->config + PCI_CLASS_DEVICE)) {
     case PCI_CLASS_STORAGE_IDE:
@@ -268,18 +284,26 @@ static void platform_fixed_ioport_writeb(void *opaque, uint32_t addr, uint32_t v
     PCIXenPlatformState *s = opaque;
 
     switch (addr) {
-    case 0: /* Platform flags */ {
-        hvmmem_type_t mem_type = (val & PFFLAG_ROM_LOCK) ?
-            HVMMEM_ram_ro : HVMMEM_ram_rw;
-        if (xen_set_mem_type(xen_domid, mem_type, 0xc0, 0x40)) {
-            DPRINTF("unable to change ro/rw state of ROM memory area!\n");
-        } else {
+    case 0: /* Platform flags */
+        if (xen_mode == XEN_EMULATE) {
+            /* XX: Use i440gx/q35 PAM setup to do this? */
             s->flags = val & PFFLAG_ROM_LOCK;
-            DPRINTF("changed ro/rw state of ROM memory area. now is %s state.\n",
-                    (mem_type == HVMMEM_ram_ro ? "ro":"rw"));
+#ifdef CONFIG_XEN
+        } else {
+            hvmmem_type_t mem_type = (val & PFFLAG_ROM_LOCK) ?
+                HVMMEM_ram_ro : HVMMEM_ram_rw;
+
+            if (xen_set_mem_type(xen_domid, mem_type, 0xc0, 0x40)) {
+                DPRINTF("unable to change ro/rw state of ROM memory area!\n");
+            } else {
+                s->flags = val & PFFLAG_ROM_LOCK;
+                DPRINTF("changed ro/rw state of ROM memory area. now is %s state.\n",
+                        (mem_type == HVMMEM_ram_ro ? "ro" : "rw"));
+            }
+#endif
         }
         break;
-    }
+
     case 2:
         log_writeb(s, val);
         break;
@@ -497,8 +521,8 @@ static void xen_platform_realize(PCIDevice *dev, Error **errp)
     uint8_t *pci_conf;
 
     /* Device will crash on reset if xen is not initialized */
-    if (!xen_enabled()) {
-        error_setg(errp, "xen-platform device requires the Xen accelerator");
+    if (xen_mode == XEN_DISABLED) {
+        error_setg(errp, "xen-platform device requires a Xen guest");
         return;
     }