[Qemu-devel] [PATCH 1/2] pcie_root_port: Allow ACS to be disabled

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

ACS was added in 4.0 unconditionally, this breaks migration
compatibility.
Allow ACS to be disabled by adding a property that's
checked by pcie_root_port.

Unfortunately pcie-root-port doesn't have any instance data,
so there's no where for that flag to live, so stuff it into
PCIESlot.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 hw/pci-bridge/pcie_root_port.c | 3 ++-
 include/hw/pci/pcie_port.h     | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/pci-bridge/pcie_root_port.c b/hw/pci-bridge/pcie_root_port.c
index 09019ca05d..1d8a778709 100644
--- a/hw/pci-bridge/pcie_root_port.c
+++ b/hw/pci-bridge/pcie_root_port.c
@@ -111,7 +111,7 @@ static void rp_realize(PCIDevice *d, Error **errp)
     pcie_aer_root_init(d);
     rp_aer_vector_update(d);
 
-    if (rpc->acs_offset) {
+    if (rpc->acs_offset && !s->disable_acs) {
         pcie_acs_init(d, rpc->acs_offset);
     }
     return;
@@ -145,6 +145,7 @@ static void rp_exit(PCIDevice *d)
 static Property rp_props[] = {
     DEFINE_PROP_BIT(COMPAT_PROP_PCP, PCIDevice, cap_present,
                     QEMU_PCIE_SLTCAP_PCP_BITNR, true),
+    DEFINE_PROP_BOOL("disable-acs", PCIESlot, disable_acs, false),
     DEFINE_PROP_END_OF_LIST()
 };
 
diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
index 09586f4641..7515430087 100644
--- a/include/hw/pci/pcie_port.h
+++ b/include/hw/pci/pcie_port.h
@@ -53,6 +53,8 @@ struct PCIESlot {
     PCIExpLinkSpeed speed;
     PCIExpLinkWidth width;
 
+    /* Disable ACS (really for a pcie_root_port) */
+    bool        disable_acs;
     QLIST_ENTRY(PCIESlot) next;
 };
 
-- 
2.21.0