Merge tag 'pull-xen-20240701' of https://xenbits.xen.org/git-http/people/aperard/qemu-dm into staging

Xen queue:

* Improvement for running QEMU in a stubdomain.
* Improve handling of buffered ioreqs.

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# gpg: Signature made Mon 01 Jul 2024 06:13:06 AM PDT
# gpg:                using RSA key F80C006308E22CFD8A92E7980CF5572FD7FB55AF
# gpg: Good signature from "Anthony PERARD <anthony.perard@gmail.com>" [undefined]
# gpg:                 aka "Anthony PERARD <anthony.perard@citrix.com>" [undefined]
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# Primary key fingerprint: 5379 2F71 024C 600F 778A  7161 D8D5 7199 DF83 42C8
#      Subkey fingerprint: F80C 0063 08E2 2CFD 8A92  E798 0CF5 572F D7FB 55AF

* tag 'pull-xen-20240701' of https://xenbits.xen.org/git-http/people/aperard/qemu-dm:
  xen-hvm: Avoid livelock while handling buffered ioreqs
  xen: fix stubdom PCI addr
  hw/xen: detect when running inside stubdomain

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

6 files changed, 122 insertions, 10 deletions

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index 006d219ad5..4f6446600c 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -584,6 +584,26 @@ static void xen_wakeup_notifier(Notifier *notifier, void *data)
     xc_set_hvm_param(xen_xc, xen_domid, HVM_PARAM_ACPI_S_STATE, 0);
 }
 
+static bool xen_check_stubdomain(struct xs_handle *xsh)
+{
+    char *dm_path = g_strdup_printf(
+        "/local/domain/%d/image/device-model-domid", xen_domid);
+    char *val;
+    int32_t dm_domid;
+    bool is_stubdom = false;
+
+    val = xs_read(xsh, 0, dm_path, NULL);
+    if (val) {
+        if (sscanf(val, "%d", &dm_domid) == 1) {
+            is_stubdom = dm_domid != 0;
+        }
+        free(val);
+    }
+
+    g_free(dm_path);
+    return is_stubdom;
+}
+
 void xen_hvm_init_pc(PCMachineState *pcms, MemoryRegion **ram_memory)
 {
     MachineState *ms = MACHINE(pcms);
@@ -596,6 +616,8 @@ void xen_hvm_init_pc(PCMachineState *pcms, MemoryRegion **ram_memory)
 
     xen_register_ioreq(state, max_cpus, &xen_memory_listener);
 
+    xen_is_stubdomain = xen_check_stubdomain(state->xenstore);
+
     QLIST_INIT(&xen_physmap);
     xen_read_physmap(state);
 
diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
index 8c6e9a1716..eaf32f2710 100644
--- a/hw/xen/xen-host-pci-device.c
+++ b/hw/xen/xen-host-pci-device.c
@@ -9,6 +9,8 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/cutils.h"
+#include "hw/xen/xen-legacy-backend.h"
+#include "hw/xen/xen-bus-helper.h"
 #include "xen-host-pci-device.h"
 
 #define XEN_HOST_PCI_MAX_EXT_CAP \
@@ -33,13 +35,73 @@
 #define IORESOURCE_PREFETCH     0x00001000      /* No side effects */
 #define IORESOURCE_MEM_64       0x00100000
 
+/*
+ * Non-passthrough (dom0) accesses are local PCI devices and use the given BDF
+ * Passthough (stubdom) accesses are through PV frontend PCI device.  Those
+ * either have a BDF identical to the backend's BDF (xen-backend.passthrough=1)
+ * or a local virtual BDF (xen-backend.passthrough=0)
+ *
+ * We are always given the backend's BDF and need to lookup the appropriate
+ * local BDF for sysfs access.
+ */
+static void xen_host_pci_fill_local_addr(XenHostPCIDevice *d, Error **errp)
+{
+    unsigned int num_devs, len, i;
+    unsigned int domain, bus, dev, func;
+    char *be_path = NULL;
+    char path[16];
+
+    be_path = qemu_xen_xs_read(xenstore, 0, "device/pci/0/backend", &len);
+    if (!be_path) {
+        error_setg(errp, "Failed to read device/pci/0/backend");
+        goto out;
+    }
+
+    if (xs_node_scanf(xenstore, 0, be_path, "num_devs", NULL,
+                      "%d", &num_devs) != 1) {
+        error_setg(errp, "Failed to read or parse %s/num_devs", be_path);
+        goto out;
+    }
+
+    for (i = 0; i < num_devs; i++) {
+        snprintf(path, sizeof(path), "dev-%d", i);
+        if (xs_node_scanf(xenstore, 0, be_path, path, NULL,
+                          "%x:%x:%x.%x", &domain, &bus, &dev, &func) != 4) {
+            error_setg(errp, "Failed to read or parse %s/%s", be_path, path);
+            goto out;
+        }
+        if (domain != d->domain ||
+                bus != d->bus ||
+                dev != d->dev ||
+                func != d->func)
+            continue;
+        snprintf(path, sizeof(path), "vdev-%d", i);
+        if (xs_node_scanf(xenstore, 0, be_path, path, NULL,
+                          "%x:%x:%x.%x", &domain, &bus, &dev, &func) != 4) {
+            error_setg(errp, "Failed to read or parse %s/%s", be_path, path);
+            goto out;
+        }
+        d->local_domain = domain;
+        d->local_bus = bus;
+        d->local_dev = dev;
+        d->local_func = func;
+        goto out;
+    }
+    error_setg(errp, "Failed to find PCI device %x:%x:%x.%x in xenstore",
+               d->domain, d->bus, d->dev, d->func);
+
+out:
+    free(be_path);
+}
+
 static void xen_host_pci_sysfs_path(const XenHostPCIDevice *d,
                                     const char *name, char *buf, ssize_t size)
 {
     int rc;
 
     rc = snprintf(buf, size, "/sys/bus/pci/devices/%04x:%02x:%02x.%d/%s",
-                  d->domain, d->bus, d->dev, d->func, name);
+                  d->local_domain, d->local_bus, d->local_dev, d->local_func,
+                  name);
     assert(rc >= 0 && rc < size);
 }
 
@@ -342,6 +404,18 @@ void xen_host_pci_device_get(XenHostPCIDevice *d, uint16_t domain,
     d->dev = dev;
     d->func = func;
 
+    if (xen_is_stubdomain) {
+        xen_host_pci_fill_local_addr(d, errp);
+        if (*errp) {
+            goto error;
+        }
+    } else {
+        d->local_domain = d->domain;
+        d->local_bus = d->bus;
+        d->local_dev = d->dev;
+        d->local_func = d->func;
+    }
+
     xen_host_pci_config_open(d, errp);
     if (*errp) {
         goto error;
diff --git a/hw/xen/xen-host-pci-device.h b/hw/xen/xen-host-pci-device.h
index 4d8d34ecb0..270dcb27f7 100644
--- a/hw/xen/xen-host-pci-device.h
+++ b/hw/xen/xen-host-pci-device.h
@@ -23,6 +23,12 @@ typedef struct XenHostPCIDevice {
     uint8_t dev;
     uint8_t func;
 
+    /* different from the above in case of stubdomain */
+    uint16_t local_domain;
+    uint8_t local_bus;
+    uint8_t local_dev;
+    uint8_t local_func;
+
     uint16_t vendor_id;
     uint16_t device_id;
     uint32_t class_code;
diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
index b8ace1c368..3a9d6f981b 100644
--- a/hw/xen/xen-hvm-common.c
+++ b/hw/xen/xen-hvm-common.c
@@ -475,11 +475,11 @@ static void handle_ioreq(XenIOState *state, ioreq_t *req)
     }
 }
 
-static bool handle_buffered_iopage(XenIOState *state)
+static unsigned int handle_buffered_iopage(XenIOState *state)
 {
     buffered_iopage_t *buf_page = state->buffered_io_page;
     buf_ioreq_t *buf_req = NULL;
-    bool handled_ioreq = false;
+    unsigned int handled = 0;
     ioreq_t req;
     int qw;
 
@@ -492,7 +492,7 @@ static bool handle_buffered_iopage(XenIOState *state)
     req.count = 1;
     req.dir = IOREQ_WRITE;
 
-    for (;;) {
+    do {
         uint32_t rdptr = buf_page->read_pointer, wrptr;
 
         xen_rmb();
@@ -533,22 +533,30 @@ static bool handle_buffered_iopage(XenIOState *state)
         assert(!req.data_is_ptr);
 
         qatomic_add(&buf_page->read_pointer, qw + 1);
-        handled_ioreq = true;
-    }
+        handled += qw + 1;
+    } while (handled < IOREQ_BUFFER_SLOT_NUM);
 
-    return handled_ioreq;
+    return handled;
 }
 
 static void handle_buffered_io(void *opaque)
 {
+    unsigned int handled;
     XenIOState *state = opaque;
 
-    if (handle_buffered_iopage(state)) {
+    handled = handle_buffered_iopage(state);
+    if (handled >= IOREQ_BUFFER_SLOT_NUM) {
+        /* We handled a full page of ioreqs. Schedule a timer to continue
+         * processing while giving other stuff a chance to run.
+         */
         timer_mod(state->buffered_io_timer,
-                BUFFER_IO_MAX_DELAY + qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
-    } else {
+                qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
+    } else if (handled == 0) {
         timer_del(state->buffered_io_timer);
         qemu_xen_evtchn_unmask(state->xce_handle, state->bufioreq_local_port);
+    } else {
+        timer_mod(state->buffered_io_timer,
+                BUFFER_IO_MAX_DELAY + qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
     }
 }
 
diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
index 37ecc91fc3..ecb89ecfc1 100644
--- a/include/hw/xen/xen.h
+++ b/include/hw/xen/xen.h
@@ -36,6 +36,7 @@ enum xen_mode {
 extern uint32_t xen_domid;
 extern enum xen_mode xen_mode;
 extern bool xen_domid_restrict;
+extern bool xen_is_stubdomain;
 
 int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num);
 int xen_set_pci_link_route(uint8_t link, uint8_t irq);
diff --git a/system/globals.c b/system/globals.c
index e353584201..d602a04fa2 100644
--- a/system/globals.c
+++ b/system/globals.c
@@ -60,6 +60,7 @@ bool qemu_uuid_set;
 uint32_t xen_domid;
 enum xen_mode xen_mode = XEN_DISABLED;
 bool xen_domid_restrict;
+bool xen_is_stubdomain;
 struct evtchn_backend_ops *xen_evtchn_ops;
 struct gnttab_backend_ops *xen_gnttab_ops;
 struct foreignmem_backend_ops *xen_foreignmem_ops;