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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] xen: Fix host pci for stubdom
Am 20. März 2023 00:05:54 UTC schrieb Jason Andryuk <jandryuk@xxxxxxxxx>:
>PCI passthrough for an HVM with a stubdom is PV PCI passthrough from
>dom0 to the stubdom, and then QEMU passthrough of the PCI device inside
>the stubdom. xen-pciback has boolean module param passthrough which
>controls "how to export PCI topology to guest". If passthrough=1, the
>frontend shows a PCI SBDF matching the backend host device. When
>passthough=0, the frontend will get a sequentially allocated SBDF.
>
>libxl passes the host SBDF over QMP to QEMU. For non-stubdom or stubdom
>with passthrough=1, this works fine. However, it fails for
>passthrough=0 when QEMU can't find the sysfs node for the host SBDF.
>
>Handle all these cases. Look for the xenstore frontend nodes. If they
>are missing, then default to using the QMP command provided SBDF. This
>is the non-stubdom case. If xenstore nodes are found, then read the
>local SBDF from the xenstore nodes. This will handle either
>passthrough=0/1 case.
>
>Based on a stubdom-specific patch originally by Marek
>Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, which is based
>on earlier work by HW42 <hw42@xxxxxxxxx>
>
>Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
>---
> hw/xen/xen-host-pci-device.c | 96 +++++++++++++++++++++++++++++++++++-
> hw/xen/xen-host-pci-device.h | 6 +++
> 2 files changed, 101 insertions(+), 1 deletion(-)
>
>diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
>index 8c6e9a1716..51a72b432d 100644
>--- a/hw/xen/xen-host-pci-device.c
>+++ b/hw/xen/xen-host-pci-device.c
>@@ -9,6 +9,7 @@
> #include "qemu/osdep.h"
> #include "qapi/error.h"
> #include "qemu/cutils.h"
>+#include "hw/xen/xen-legacy-backend.h"
> #include "xen-host-pci-device.h"
>
> #define XEN_HOST_PCI_MAX_EXT_CAP \
>@@ -33,13 +34,101 @@
> #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
I'm unable to parse this sentence, which may be due to my unfamiliarity with
Xen terminology.
There is also an extra space before "Those".
Best regards,
Bernhard
>+ * either have a BDF identical to the backend's BFD
>(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;
>+ char path[80];
>+ char *msg;
>+
>+ be_path = qemu_xen_xs_read(xenstore, 0, "device/pci/0/backend", &len);
>+ if (!be_path) {
>+ /*
>+ * be_path doesn't exist, so we are dealing with a local
>+ * (non-passthough) device.
>+ */
>+ d->local_domain = d->domain;
>+ d->local_bus = d->bus;
>+ d->local_dev = d->dev;
>+ d->local_func = d->func;
>+
>+ return;
>+ }
>+
>+ snprintf(path, sizeof(path), "%s/num_devs", be_path);
>+ msg = qemu_xen_xs_read(xenstore, 0, path, &len);
>+ if (!msg) {
>+ goto err_out;
>+ }
>+
>+ if (sscanf(msg, "%u", &num_devs) != 1) {
>+ error_setg(errp, "Failed to parse %s (%s)", msg, path);
>+ goto err_out;
>+ }
>+ free(msg);
>+
>+ for (i = 0; i < num_devs; i++) {
>+ snprintf(path, sizeof(path), "%s/dev-%u", be_path, i);
>+ msg = qemu_xen_xs_read(xenstore, 0, path, &len);
>+ if (!msg) {
>+ error_setg(errp, "Failed to read %s", path);
>+ goto err_out;
>+ }
>+ if (sscanf(msg, "%x:%x:%x.%x", &domain, &bus, &dev, &func) != 4) {
>+ error_setg(errp, "Failed to parse %s (%s)", msg, path);
>+ goto err_out;
>+ }
>+ free(msg);
>+ if (domain != d->domain ||
>+ bus != d->bus ||
>+ dev != d->dev ||
>+ func != d->func)
>+ continue;
>+ snprintf(path, sizeof(path), "%s/vdev-%u", be_path, i);
>+ msg = qemu_xen_xs_read(xenstore, 0, path, &len);
>+ if (!msg) {
>+ error_setg(errp, "Failed to read %s", path);
>+ goto out;
>+ }
>+ if (sscanf(msg, "%x:%x:%x.%x", &domain, &bus, &dev, &func) != 4) {
>+ error_setg(errp, "Failed to parse %s (%s)", msg, path);
>+ goto err_out;
>+ }
>+ free(msg);
>+ d->local_domain = domain;
>+ d->local_bus = bus;
>+ d->local_dev = dev;
>+ d->local_func = func;
>+ goto out;
>+ }
>+
>+ error_setg(errp, "Failed to find local %x:%x:%x.%x", d->domain, d->bus,
>+ d->dev, d->func);
>+
>+err_out:
>+ free(msg);
>+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 +431,11 @@ void xen_host_pci_device_get(XenHostPCIDevice *d,
>uint16_t domain,
> d->dev = dev;
> d->func = func;
>
>+ xen_host_pci_fill_local_addr(d, errp);
>+ if (*errp) {
>+ goto error;
>+ }
>+
> 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;
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