configure pci slot removability through ACPI

Expose no_hotplug attribute via I/O port, so ACPI BIOS can indicate removability status to guest OS.

An updated seabios is required to make use of this feature (seabios.git commit ID 3c241edf3d7ef29c21).

Signed-off-by Marcelo Tosatti <[email protected]>

Tested-by Gleb Natapov <[email protected]>

Index: qemu/hw/acpi_piix4.c
===================================================================

hw/acpi_piix4.c +11 -0

@@ -37,6 +37,7 @@
 #define GPE_BASE 0xafe0
 #define PCI_BASE 0xae00
 #define PCI_EJ_BASE 0xae08
+#define PCI_RMV_BASE 0xae0c
 
 #define PIIX4_PCI_HOTPLUG_STATUS 2
 

@@ -73,6 +74,7 @@ typedef struct PIIX4PMState {
     /* for pci hotplug */
     struct gpe_regs gpe;
     struct pci_status pci0_status;
+    uint32_t pci0_hotplug_enable;
 } PIIX4PMState;
 
 static void piix4_acpi_system_hot_add_init(PCIBus *bus, PIIX4PMState *s);

@@ -322,6 +324,25 @@ static const VMStateDescription vmstate_
     }
 };
 
+static void piix4_update_hotplug(PIIX4PMState *s)
+{
+    PCIDevice *dev = &s->dev;
+    BusState *bus = qdev_get_parent_bus(&dev->qdev);
+    DeviceState *qdev, *next;
+
+    s->pci0_hotplug_enable = 0;
+
+    QLIST_FOREACH_SAFE(qdev, &bus->children, sibling, next) {

hw/acpi_piix4.c +16 -0

 static void piix4_reset(void *opaque)
 {
     PIIX4PMState *s = opaque;

@@ -336,6 +357,7 @@ static void piix4_reset(void *opaque)
         /* Mark SMM as already inited (until KVM supports SMM). */
         pci_conf[0x5B] = 0x02;
     }
+    piix4_update_hotplug(s);
 }
 
 static void piix4_powerdown(void *opaque, int irq, int power_failing)

@@ -576,6 +598,18 @@ static void pciej_write(void *opaque, ui
     PIIX4_DPRINTF("pciej write %x <== %d\n", addr, val);
 }
 
+static uint32_t pcirmv_read(void *opaque, uint32_t addr)
+{
+    PIIX4PMState *s = opaque;
+
+    return s->pci0_hotplug_enable;
+}
+
+static void pcirmv_write(void *opaque, uint32_t addr, uint32_t val)
+{
+    return;
+}
+
 static int piix4_device_hotplug(DeviceState *qdev, PCIDevice *dev,
                                 PCIHotplugState state);
 

@@ -592,6 +626,9 @@ static void piix4_acpi_system_hot_add_in
     register_ioport_write(PCI_EJ_BASE, 4, 4, pciej_write, bus);
     register_ioport_read(PCI_EJ_BASE, 4, 4,  pciej_read, bus);
 
+    register_ioport_write(PCI_RMV_BASE, 4, 4, pcirmv_write, s);
+    register_ioport_read(PCI_RMV_BASE, 4, 4,  pcirmv_read, s);
+
     pci_bus_hotplug(bus, piix4_device_hotplug, &s->dev.qdev);
 }
 

Quoted 49 lines · Marcelo Tosatti

Expose no_hotplug attribute via I/O port, so ACPI BIOS can indicate removability status to guest OS.

An updated seabios is required to make use of this feature (seabios.git commit ID 3c241edf3d7ef29c21).

Signed-off-by Marcelo Tosatti <[email protected]>

Tested-by Gleb Natapov <[email protected]>

Index: qemu/hw/acpi_piix4.c
===================================================================

hw/acpi_piix4.c +18 -0

@@ -37,6 +37,7 @@
 #define GPE_BASE 0xafe0
 #define PCI_BASE 0xae00
 #define PCI_EJ_BASE 0xae08
+#define PCI_RMV_BASE 0xae0c
 
 #define PIIX4_PCI_HOTPLUG_STATUS 2
 

@@ -73,6 +74,7 @@ typedef struct PIIX4PMState {
     /* for pci hotplug */
     struct gpe_regs gpe;
     struct pci_status pci0_status;
+    uint32_t pci0_hotplug_enable;
 } PIIX4PMState;
 
 static void piix4_acpi_system_hot_add_init(PCIBus *bus, PIIX4PMState *s);

@@ -322,6 +324,25 @@ static const VMStateDescription vmstate_
     }
 };
 
+static void piix4_update_hotplug(PIIX4PMState *s)
+{
+    PCIDevice *dev = &s->dev;
+    BusState *bus = qdev_get_parent_bus(&dev->qdev);
+    DeviceState *qdev, *next;
+
+    s->pci0_hotplug_enable = 0;
+
+    QLIST_FOREACH_SAFE(qdev, &bus->children, sibling, next) {
+        PCIDeviceInfo *info = container_of(qdev->info, PCIDeviceInfo, qdev);
+        PCIDevice *pdev = DO_UPCAST(PCIDevice, qdev, qdev);
+        int slot = PCI_SLOT(pdev->devfn);
+
+        if (!info->no_hotplug) {
+            s->pci0_hotplug_enable |= (1 << slot);
+        }

hw/acpi_piix4.c static const VMStateDescription vmstate_ · line 345

Quoted 3 lines

hw/acpi_piix4.c +3 -0

+    }
+}
+

So a slot starts as non-removable and becomes removable when you add a hotpluggable device? Isn't this a bit strange?
I would say all slots should be removable unless there's a non hotpluggable device there ...

Document how QEMU communicates with ACPI BIOS for PCI hotplug.

Signed-off-by Marcelo Tosatti <[email protected]>

Index: qemu/docs/specs/acpi_pci_hotplug.txt
===================================================================

docs/specs/acpi_pci_hotplug.txt new file +39 -0

@@ -0,0 +1,39 @@
+QEMU<->ACPI BIOS PCI hotplug interface
+--------------------------------------
+
+QEMU supports PCI hotplug via ACPI, for PCI bus 0. This document
+describes the interface between QEMU and the ACPI BIOS.
+
+ACPI GPE block (IO ports 0xafe0-0xafe3, byte access):
+-----------------------------------------
+
+Generic ACPI GPE block. Bit 1 (GPE.1) used to notify PCI hotplug/eject
+event to ACPI BIOS, via SCI interrupt.
+
+PCI slot injection notification pending (IO port 0xae00-0xae03, 4-byte access):
+---------------------------------------------------------------
+Slot injection notification pending. One bit per slot.
+
+Read by ACPI BIOS GPE.1 handler to notify OS of injection
+events.
+
+PCI slot removal notification (IO port 0xae04-0xae07, 4-byte access):
+-----------------------------------------------------
+Slot removal notification pending. One bit per slot.
+
+Read by ACPI BIOS GPE.1 handler to notify OS of removal
+events.
+
+PCI device eject (IO port 0xae08-0xae0b, 4-byte access):
+----------------------------------------
+
+Used by ACPI BIOS _EJ0 method to request device removal. One bit per slot.
+Reads return 0.
+
+PCI removability status (IO port 0xae0c-0xae0f, 4-byte access):
+-----------------------------------------------
+
+Used by ACPI BIOS _RMV method to indicate removability status to OS. One
+bit per slot.
+
+