Re: [Qemu-devel] usb: usb tablet freeze when save/restore guest os

[Gonglei (Arei)]

Signed-off-by: Gonglei <address@hidden>
---
 hw/usb/hcd-uhci.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/usb/hcd-uhci.c b/hw/usb/hcd-uhci.c
index 0820244..fe0ad81 100644
--- a/hw/usb/hcd-uhci.c
+++ b/hw/usb/hcd-uhci.c
@@ -680,6 +680,12 @@ static void uhci_wakeup(USBPort *port1)
 {
     UHCIState *s = port1->opaque;
     UHCIPort *port = &s->ports[port1->index];
+    uint8_t *pci_conf = s->dev.config;
+
+    /* Do not resume UHCI when UHCI PIRQ was disabled */
+    if (pci_conf[0xc1] == 0x00 && pci_conf[0xc0] == 0x00) {
+        return;
+    }

     if (port->ctrl & UHCI_PORT_SUSPEND && !(port->ctrl & UHCI_PORT_RD)) {
         port->ctrl |= UHCI_PORT_RD;
@@ -1241,6 +1247,10 @@ static int usb_uhci_common_initfn(PCIDevice *dev)
     /* TODO: reset value should be 0. */
     pci_conf[USB_SBRN] = USB_RELEASE_1; // release number

+    /* LEGACY SUPPORT REGISTER - UHCI11D 5.2.1 */
+    pci_conf[0xc0] |= 0x00;
+    pci_conf[0xc1] |= 0x20; /* Enable USB PIRQ */
+
     pci_config_set_interrupt_pin(pci_conf, u->info.irq_pin + 1);

     if (s->masterbus) {
-- 
1.7.12.4

> -----Original Message-----
> From: Gonglei (Arei)
> Sent: Tuesday, May 13, 2014 5:05 PM
> To: address@hidden
> Cc: 'Gerd Hoffmann'; Huangweidong (C); 'Michael S. Tsirkin'
> Subject: usb: usb tablet freeze when save/restore guest os
> 
> Hi,
> 
> For recent Linux guests, the usb tablet will be suspended when it is idle.
> When Qemu detect the usb tablet event, will call uhci_wakeup(), which
> according the value of port->ctrl to decide to call uhci_resume() or not.
> UHCI_PORT_RD bit is set to 1 for UHCI is resuming, and qemu will not call
> uhci_resume(). The other way round, qemu will call uhci_resume() and then
> post a interrupt to guest os, meanwhile set UHCI_PORT_RD bit to 1.
> 
> In the guests, after handle the interrupt, will call uhci_finish_suspend(), 
> which
> clear UHCI_PORT_RD bit, Then qemu will know that the UHCI resume
> process has finished.
> 
> In the situation of save/restore guest os, when the guest os is saving
> memory iteratively, meanwhile the usb tablet work normally (by vnc). When
> qemu
> has set the UHCI_PORT_RD bit to 1, and post a interrupt to guest os, but
> guest os has hibernated this moment, so the interrupt cannot be handled
> in time. So, the UHCI_PORT_RD bit will not be cleared by 
> uhci_finish_suspend().
> 
> When we restore the guest os, and the usb tablet event happen again, but
> because of UHCI_PORT_RD bit being set to 1, qemu consider the guest os is
> handling the interrupt of resuming UHCI, so will not post another interrupt.
> For guest os, will not handle UHCI event because it not receive an interrupt,
> which cause usb tablet freeze.
> 
> So, we should provide a mechanism for avoiding losing interrupt of UHCI.
> IMHO the LEGACY SUPPORT REGISTER will give us some help, and I have
> finished a patch and tested it work well.
> 
> Anything idea? Thanks!
> 
> 
> Best regards,
> -Gonglei
>