Re: [PATCH v1] piix: fix regression during unplug in Xen HVM domUs

[Philippe Mathieu-Daudé]

On 3/16/21 11:44 PM, Olaf Hering wrote:
> Commit ee358e919e385fdc79d59d0d47b4a81e349cd5c9 causes a regression in
> Xen HVM domUs which run xenlinux based kernels.
> 
> If the domU has an USB device assigned, for example with
> "usbdevice=['tablet']" in domU.cfg, the late unplug of devices will
> kill the emulated USB host. As a result the khubd thread hangs, and as
> a result the entire boot process.
> 
> For some reason this does not affect pvops based kernels. This is
> most likely caused by the fact that unplugging happens very early
> during boot.
> 
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> ---
>  hw/ide/piix.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/hw/ide/piix.c b/hw/ide/piix.c
> index b9860e35a5..2a380a90e9 100644
> --- a/hw/ide/piix.c
> +++ b/hw/ide/piix.c
> @@ -34,6 +34,7 @@
>  #include "hw/ide/pci.h"
>  #include "trace.h"
>  
> +static bool pci_piix3_xen_ide_unplug_done;

This field belongs to the device state (PCIIDEState or BMDMAState).

>  static uint64_t bmdma_read(void *opaque, hwaddr addr, unsigned size)
>  {
>      BMDMAState *bm = opaque;
> @@ -109,6 +110,8 @@ static void piix_ide_reset(DeviceState *dev)
>      uint8_t *pci_conf = pd->config;
>      int i;
>  
> +    if (pci_piix3_xen_ide_unplug_done == true)
> +        return;
>      for (i = 0; i < 2; i++) {
>          ide_bus_reset(&d->bus[i]);
>      }
> @@ -169,6 +172,7 @@ int pci_piix3_xen_ide_unplug(DeviceState *dev, bool aux)
>      IDEBus *idebus;
>      BlockBackend *blk;
>  
> +    pci_piix3_xen_ide_unplug_done = true;
>      pci_ide = PCI_IDE(dev);
>  
>      for (i = aux ? 1 : 0; i < 4; i++) {
> @@ -259,6 +263,7 @@ static const TypeInfo piix4_ide_info = {
>  
>  static void piix_ide_register_types(void)
>  {
> +    pci_piix3_xen_ide_unplug_done = false;
>      type_register_static(&piix3_ide_info);
>      type_register_static(&piix3_ide_xen_info);
>      type_register_static(&piix4_ide_info);
>