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

[Steven Sistare]

On 2/4/2025 9:14 AM, Cédric Le Goater wrote:

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

Do not reset a vfio-pci device during CPR.

Signed-off-by: Steve Sistare 
---
  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.


OK.


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


pci_do_device_reset is also called from pcibus_reset_hold.

- Steve


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

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 
---
  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);
  

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

[Steve Sistare]

Do not reset a vfio-pci device during CPR.

Signed-off-by: Steve Sistare 
---
 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;
+}
+
 pci_device_deassert_intx(dev);
 assert(dev->irq_state == 0);
 
-- 
1.8.3.1