From: Steve Sistare <steven.sistare@oracle.com>
Date: Tue, 10 Jun 2025 17:26:43 +0000 (-0700)
Subject: pci: skip reset during cpr
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=24c156dcd94299f64994170ce84efac9ae001f41;p=thirdparty%2Fqemu.git

pci: skip reset during cpr

Do not reset a vfio-pci device during CPR.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/qemu-devel/1749576403-25355-1-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 9b4bf48439..c70b5ceeba 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -32,6 +32,7 @@
 #include "hw/pci/pci_host.h"
 #include "hw/qdev-properties.h"
 #include "hw/qdev-properties-system.h"
+#include "migration/cpr.h"
 #include "migration/qemu-file-types.h"
 #include "migration/vmstate.h"
 #include "net/net.h"
@@ -537,6 +538,10 @@ static void pci_reset_regions(PCIDevice *dev)
 
 static void pci_do_device_reset(PCIDevice *dev)
 {
+    if ((dev->cap_present & QEMU_PCI_SKIP_RESET_ON_CPR) && cpr_is_incoming()) {
+        return;
+    }
+
     pci_device_deassert_intx(dev);
     assert(dev->irq_state == 0);
 
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 89f9246416..b97261c61b 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3411,6 +3411,13 @@ static void vfio_instance_init(Object *obj)
     /* QEMU_PCI_CAP_EXPRESS initialization does not depend on QEMU command
      * line, therefore, no need to wait to realize like other devices */
     pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
+
+    /*
+     * A device that is resuming for cpr is already configured, so do not
+     * reset it during qemu_system_reset prior to cpr load, else interrupts
+     * may be lost.
+     */
+    pci_dev->cap_present |= QEMU_PCI_SKIP_RESET_ON_CPR;
 }
 
 static void vfio_pci_base_dev_class_init(ObjectClass *klass, const void *data)
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 35d59d7672..df3cc7b875 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -222,6 +222,8 @@ enum {
     QEMU_PCIE_EXT_TAG = (1 << QEMU_PCIE_EXT_TAG_BITNR),
 #define QEMU_PCI_CAP_PM_BITNR 14
     QEMU_PCI_CAP_PM = (1 << QEMU_PCI_CAP_PM_BITNR),
+#define QEMU_PCI_SKIP_RESET_ON_CPR_BITNR 15
+    QEMU_PCI_SKIP_RESET_ON_CPR = (1 << QEMU_PCI_SKIP_RESET_ON_CPR_BITNR),
 };
 
 typedef struct PCIINTxRoute {