[v5,1/6] libxl: do not attach xen-pciback to HVM domain, if stubdomain is in use
diff mbox series

Message ID 5b6a20c0b33a2b52175174a27ce388208f932992.1563325215.git-series.marmarek@invisiblethingslab.com
State Superseded
Headers show
  • Fix PCI passthrough for HVM with stubdomain
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Commit Message

Marek Marczykowski-Górecki July 17, 2019, 1 a.m. UTC
HVM domains use IOMMU and device model assistance for communicating with
PCI devices, xen-pcifront/pciback isn't directly needed by HVM domain.
But pciback serve also second function - it reset the device when it is
deassigned from the guest and for this reason pciback needs to be used
with HVM domain too.
When HVM domain has device model in stubdomain, attaching xen-pciback to
the target domain itself may prevent attaching xen-pciback to the
(PV) stubdomain, effectively breaking PCI passthrough.

Fix this by attaching pciback only to one domain: if PV stubdomain is in
use, let it be stubdomain (the commit prevents attaching device to target
HVM in this case); otherwise, attach it to the target domain.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Changes in v2:
 - previously called "libxl: attach xen-pciback only to PV domains"
 - instead of excluding all HVMs, change the condition to what actually
   matters here - check if stubdomain is in use; this way xen-pciback is
   always in use (either for the target domain, or it's stubdomain),
   fixing PCI reset by xen-pciback concerns
Changes in v3:
 - adjust commit message
 tools/libxl/libxl_pci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff mbox series

diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
index 4ec6872..7ffab89 100644
--- a/tools/libxl/libxl_pci.c
+++ b/tools/libxl/libxl_pci.c
@@ -1106,7 +1106,7 @@  out:
-    if (!starting)
+    if (!starting && !libxl_get_stubdom_id(CTX, domid))
         rc = libxl__device_pci_add_xenstore(gc, domid, pcidev, starting);
         rc = 0;
@@ -1302,7 +1302,7 @@  static void libxl__add_pcidevs(libxl__egc *egc, libxl__ao *ao, uint32_t domid,
-    if (d_config->num_pcidevs > 0) {
+    if (d_config->num_pcidevs > 0 && !libxl_get_stubdom_id(CTX, domid)) {
         rc = libxl__create_pci_backend(gc, domid, d_config->pcidevs,
         if (rc < 0) {