Re: [PATCH V1 08/26] pci: skip reset during cpr

[Cédric Le Goater]

On 1/29/25 15:43, Steve Sistare wrote:

Do not reset a vfio-pci device during CPR.

Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
  hw/pci/pci.c | 13 +++++++++++++
  1 file changed, 13 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 2afa423..16b4f71 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/misc.h"
  #include "migration/qemu-file-types.h"
  #include "migration/vmstate.h"
  #include "net/net.h"
@@ -459,6 +460,18 @@ static void pci_reset_regions(PCIDevice *dev)

static void pci_do_device_reset(PCIDevice *dev)

  {
+    /*
+     * A PCI device that is resuming for cpr is already configured, so do
+     * not reset it here when we are called from qemu_system_reset prior to
+     * cpr load, else interrupts may be lost for vfio-pci devices.  It is
+     * safe to skip this reset for all PCI devices, because cpr load will set
+     * all fields that would have been set here.
+     */
+    MigMode mode = migrate_mode();
+    if (mode == MIG_MODE_CPR_TRANSFER) {
+        return;
+    }

Please use cpr_needed_for_reuse(). Or an appropriate helper.

I would the test under pci_device_reset() and avoid calling
pci_do_device_reset().

Thanks,

C.

      pci_device_deassert_intx(dev);
      assert(dev->irq_state == 0);