[QEMU,RFC,V2,07/10] xen: specify which device is part of default devices

One major problem of QEMU disaggregation is that some devices needs to
be "emulate" in each QEMU, but only one need to register it in Xen.

This patch introduces helpers that can be used in QEMU code (for
instance hw/pc_piix.c) to specify if the device is part of default sets.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
---
 hw/pc_piix.c |    2 ++
 hw/xen.h     |   20 ++++++++++++++++++++
 xen-all.c    |   29 +++++++++++++++++++++++++++--
 3 files changed, 49 insertions(+), 2 deletions(-)

On Wed, 22 Aug 2012, Julien Grall wrote:
> One major problem of QEMU disaggregation is that some devices needs to
> be "emulate" in each QEMU, but only one need to register it in Xen.
> 
> This patch introduces helpers that can be used in QEMU code (for
> instance hw/pc_piix.c) to specify if the device is part of default sets.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> ---
>  hw/pc_piix.c |    2 ++
>  hw/xen.h     |   20 ++++++++++++++++++++
>  xen-all.c    |   29 +++++++++++++++++++++++++++--
>  3 files changed, 49 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 0c0096f..6cb0a2a 100644
> --- a/hw/pc_piix.c
> +++ b/hw/pc_piix.c
> @@ -342,9 +342,11 @@ static void pc_xen_hvm_init(ram_addr_t ram_size,
>      if (xen_hvm_init() != 0) {
>          hw_error("xen hardware virtual machine initialisation failed");
>      }
> +    xen_set_register_default_dev(1,  NULL);
>      pc_init_pci_no_kvmclock(ram_size, boot_device,
>                              kernel_filename, kernel_cmdline,
>                              initrd_filename, cpu_model);
> +    xen_set_register_default_dev(0, NULL);
>      xen_vcpu_init();
>  }

Honestly I don't like this interface, I would rather have an explicit
list of "default devices" and then go through them in
xen_register_pcidev and xen_map_iorange.


>  #endif
> diff --git a/hw/xen.h b/hw/xen.h
> index 663731a..3c8724f 100644
> --- a/hw/xen.h
> +++ b/hw/xen.h
> @@ -21,6 +21,7 @@ extern uint32_t xen_domid;
>  extern enum xen_mode xen_mode;
>  
>  extern int xen_allowed;
> +extern int xen_register_default_dev;
>  
>  static inline int xen_enabled(void)
>  {
> @@ -31,6 +32,25 @@ static inline int xen_enabled(void)
>  #endif
>  }
>  
> +static inline int xen_is_registered_default_dev(void)
> +{
> +#if defined(CONFIG_XEN)
> +    return xen_register_default_dev;
> +#else
> +    return 1;
> +#endif
> +}
> +
> +static inline void xen_set_register_default_dev(int val, int *old)
> +{
> +#if defined(CONFIG_XEN)
> +    if (old) {
> +        *old = xen_register_default_dev;
> +    }
> +    xen_register_default_dev = val;
> +#endif
> +}
> +
>  int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num);
>  void xen_piix3_set_irq(void *opaque, int irq_num, int level);
>  void xen_piix_pci_write_config_client(uint32_t address, uint32_t val, int len);
> diff --git a/xen-all.c b/xen-all.c
> index 485c312..afa9bcc 100644
> --- a/xen-all.c
> +++ b/xen-all.c
> @@ -39,6 +39,10 @@ static MemoryRegion *framebuffer;
>  static unsigned int serverid;
>  static uint32_t xen_dmid = ~0;
>  
> +/* Use to tell if we register pci/mmio/pio of default devices */
> +int xen_register_default_dev = 0;
> +static int xen_emulate_default_dev = 1;
>
>  /* Compatibility with older version */
>  #if __XEN_LATEST_INTERFACE_VERSION__ < 0x0003020a
>  static inline uint32_t xen_vcpu_eport(shared_iopage_t *shared_page, int i)
> @@ -176,6 +180,10 @@ void xen_piix3_set_irq(void *opaque, int irq_num, int level)
>  
>  int xen_register_pcidev(PCIDevice *pci_dev)
>  {
> +    if (xen_register_default_dev && !xen_emulate_default_dev) {
> +        return 0;
> +    }
>
>      DPRINTF("register pci %x:%x.%x %s\n", 0, (pci_dev->devfn >> 3) & 0x1f,
>              pci_dev->devfn & 0x7, pci_dev->name);
>  
> @@ -214,6 +222,18 @@ static void xen_map_iorange(target_phys_addr_t addr, uint64_t size,
>          return;
>      }
>  
> +    /* Handle the registration of all default io range */
> +    if (xen_register_default_dev) {
> +        /* Register ps/2 only if we emulate VGA */
> +        if (!strcmp(name, "i8042-data") || !strcmp(name, "i8042-cmd")) {
> +            if (display_type == DT_NOGRAPHIC) {
> +                return;
> +            }
> +        } else if (!xen_emulate_default_dev && strcmp(name, "serial")) {
> +            return;
> +        }
> +    }

It seems to be that you are acting upon xen_register_default_dev only in
xen_map_iorange and xen_register_pcidev, so it shouldn't be difficult to
have a real list of "default devices" instead.


>      DPRINTF("map %s %s 0x"TARGET_FMT_plx" - 0x"TARGET_FMT_plx"\n",
>              (is_mmio) ? "mmio" : "io", name, addr, addr + size - 1);
>  
> @@ -1300,6 +1320,8 @@ int xen_hvm_init(void)
>      if (!QTAILQ_EMPTY(&list->head)) {
>          xen_dmid = qemu_opt_get_number(QTAILQ_FIRST(&list->head),
>                                         "xen_dmid", ~0);
> +        xen_emulate_default_dev = qemu_opt_get_bool(QTAILQ_FIRST(&list->head),
> +                                                    "xen_default_dev", 1);
>      }
>  
>      state = g_malloc0(sizeof (XenIOState));
> @@ -1395,9 +1417,12 @@ int xen_hvm_init(void)
>          fprintf(stderr, "%s: xen backend core setup failed\n", __FUNCTION__);
>          exit(1);
>      }
> -    xen_be_register("console", &xen_console_ops);
> -    xen_be_register("vkbd", &xen_kbdmouse_ops);
>      xen_be_register("qdisk", &xen_blkdev_ops);
> +
> +    if (xen_emulate_default_dev) {
> +        xen_be_register("console", &xen_console_ops);
> +        xen_be_register("vkbd", &xen_kbdmouse_ops);
> +    }
>      xen_read_physmap(state);