Re: [RFC PATCH v2 07/22] pc_piix: handle XEN_EMULATE backend init

[Paul Durrant]

On 09/12/2022 09:55, David Woodhouse wrote:
> From: Joao Martins <joao.m.martins@oracle.com>
>
> And use newly added xen_emulated_machine_init() to iniitalize
> the xenstore and the sysdev bus for future emulated devices.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> [dwmw2: Move it to xen-legacy-backend.c]
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   hw/i386/pc_piix.c                   |  5 +++++
>   hw/xen/xen-legacy-backend.c         | 22 ++++++++++++++++------
>   include/hw/xen/xen-legacy-backend.h |  2 ++
>   3 files changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 13286d0739..3dcac2f4b6 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -47,6 +47,7 @@
>   #include "hw/sysbus.h"
>   #include "hw/i2c/smbus_eeprom.h"
>   #include "hw/xen/xen-x86.h"
> +#include "hw/xen/xen-legacy-backend.h"
>   #include "exec/memory.h"
>   #include "hw/acpi/acpi.h"
>   #include "hw/acpi/piix4.h"
> @@ -155,6 +156,10 @@ static void pc_init1(MachineState *machine,
>               x86ms->above_4g_mem_size = 0;
>               x86ms->below_4g_mem_size = machine->ram_size;
>           }
> +
> +        if (pcms->xen_version && !xen_be_xenstore_open()) {

So, this is a bit subtle... it's only *because* using real Xen results 
in xen_version being 0 that this is sane? Also does this not mean that 
we are now relying on libxenstore? Shouldn't that be called out in the 
config?

> +            xen_emulated_machine_init();
> +        }
>       }
>   
>       pc_machine_init_sgx_epc(pcms);
> diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
> index 694e7bbc54..60a7bc7ab6 100644
> --- a/hw/xen/xen-legacy-backend.c
> +++ b/hw/xen/xen-legacy-backend.c
> @@ -31,6 +31,7 @@
>   #include "qapi/error.h"
>   #include "hw/xen/xen-legacy-backend.h"
>   #include "hw/xen/xen_pvdev.h"
> +#include "hw/xen/xen-bus.h"
>   #include "monitor/qdev.h"
>   
>   DeviceState *xen_sysdev;
> @@ -294,13 +295,15 @@ static struct XenLegacyDevice *xen_be_get_xendev(const 
> char *type, int dom,
>       xendev->debug      = debug;
>       xendev->local_port = -1;
>   
> -    xendev->evtchndev = xenevtchn_open(NULL, 0);
> -    if (xendev->evtchndev == NULL) {
> -        xen_pv_printf(NULL, 0, "can't open evtchn device\n");
> -        qdev_unplug(DEVICE(xendev), NULL);
> -        return NULL;
> +    if (xen_mode != XEN_EMULATE) {
> +        xendev->evtchndev = xenevtchn_open(NULL, 0);

Doesn't this need stubbing out so that we can build without libxenevtchn?

  Paul

> +        if (xendev->evtchndev == NULL) {
> +            xen_pv_printf(NULL, 0, "can't open evtchn device\n");
> +            qdev_unplug(DEVICE(xendev), NULL);
> +            return NULL;
> +        }
> +        qemu_set_cloexec(xenevtchn_fd(xendev->evtchndev));
>       }
> -    qemu_set_cloexec(xenevtchn_fd(xendev->evtchndev));
>   
>       xen_pv_insert_xendev(xendev);
>   
> @@ -859,3 +862,10 @@ static void xenbe_register_types(void)
>   }
>   
>   type_init(xenbe_register_types)
> +
> +void xen_emulated_machine_init(void)
> +{
> +    xen_bus_init();
> +    xen_be_sysdev_init();
> +    xen_be_register_common();
> +}
> diff --git a/include/hw/xen/xen-legacy-backend.h 
> b/include/hw/xen/xen-legacy-backend.h
> index 0aa171f6c2..aa09015662 100644
> --- a/include/hw/xen/xen-legacy-backend.h
> +++ b/include/hw/xen/xen-legacy-backend.h
> @@ -105,4 +105,6 @@ int xen_config_dev_vfb(int vdev, const char *type);
>   int xen_config_dev_vkbd(int vdev);
>   int xen_config_dev_console(int vdev);
>   
> +void xen_emulated_machine_init(void);
> +
>   #endif /* HW_XEN_LEGACY_BACKEND_H */