RE: [PATCH v3] xen: fix build without pci passthrough

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Sent: 03 June 2020 17:05
> To: qemu-devel@xxxxxxxxxx
> Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>; Roger Pau Monne 
> <roger.pau@xxxxxxxxxx>; Michael S.
> Tsirkin <mst@xxxxxxxxxx>; Marcel Apfelbaum <marcel.apfelbaum@xxxxxxxxx>; 
> Paolo Bonzini
> <pbonzini@xxxxxxxxxx>; Richard Henderson <rth@xxxxxxxxxxx>; Eduardo Habkost 
> <ehabkost@xxxxxxxxxx>;
> Stefano Stabellini <sstabellini@xxxxxxxxxx>; Paul Durrant <paul@xxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx
> Subject: [PATCH v3] xen: fix build without pci passthrough
> 
> From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
> 
> Xen PCI passthrough support may not be available and thus the global
> variable "has_igd_gfx_passthru" might be compiled out. Common code
> should not access it in that case.
> 
> Unfortunately, we can't use CONFIG_XEN_PCI_PASSTHROUGH directly in
> xen-common.c so this patch instead move access to the
> has_igd_gfx_passthru variable via function and those functions are
> also implemented as stubs. The stubs will be used when QEMU is built
> without passthrough support.
> 
> Now, when one will want to enable igd-passthru via the -machine
> property, they will get an error message if QEMU is built without
> passthrough support.
> 
> Fixes: 46472d82322d0 ('xen: convert "-machine igd-passthru" to an accelerator 
> property')
> Reported-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

Acked-by: Paul Durrant <paul@xxxxxxx>

> ---
> 
> Notes:
>     Changes in v3:
>     - reworked to use stubs instead of #ifdef CONFIG_XEN_PCI_PASSTHROUGH
>       CONFIG_XEN_PCI_PASSTHROUGH isn't available in xen-common.c
> 
>       moving CONFIG_XEN_PCI_PASSTHROUGH to be in config_host_mak isn't
>       really possible, or at least I didn't managed to make that work.
> 
>  hw/i386/pc_piix.c   |  2 +-
>  hw/xen/xen-common.c |  4 ++--
>  hw/xen/xen_pt.c     | 12 +++++++++++-
>  hw/xen/xen_pt.h     |  6 ++++--
>  stubs/Makefile.objs |  1 +
>  stubs/xen-pt.c      | 22 ++++++++++++++++++++++
>  6 files changed, 41 insertions(+), 6 deletions(-)
>  create mode 100644 stubs/xen-pt.c
> 
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index f66e1d73ce0b..347fb8c6c807 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -375,7 +375,7 @@ static void pc_init_isa(MachineState *machine)
>  #ifdef CONFIG_XEN
>  static void pc_xen_hvm_init_pci(MachineState *machine)
>  {
> -    const char *pci_type = has_igd_gfx_passthru ?
> +    const char *pci_type = xen_igd_gfx_pt_enabled() ?
>                  TYPE_IGD_PASSTHROUGH_I440FX_PCI_DEVICE : 
> TYPE_I440FX_PCI_DEVICE;
> 
>      pc_init1(machine,
> diff --git a/hw/xen/xen-common.c b/hw/xen/xen-common.c
> index 70564cc952d5..dd2c22cc4c0b 100644
> --- a/hw/xen/xen-common.c
> +++ b/hw/xen/xen-common.c
> @@ -129,12 +129,12 @@ static void xen_change_state_handler(void *opaque, int 
> running,
> 
>  static bool xen_get_igd_gfx_passthru(Object *obj, Error **errp)
>  {
> -    return has_igd_gfx_passthru;
> +    return xen_igd_gfx_pt_enabled();
>  }
> 
>  static void xen_set_igd_gfx_passthru(Object *obj, bool value, Error **errp)
>  {
> -    has_igd_gfx_passthru = value;
> +    xen_igd_gfx_pt_set(value, errp);
>  }
> 
>  static void xen_setup_post(MachineState *ms, AccelState *accel)
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index 81d5ad8da7f0..ab84443d5ec8 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -65,7 +65,17 @@
>  #include "qemu/range.h"
>  #include "exec/address-spaces.h"
> 
> -bool has_igd_gfx_passthru;
> +static bool has_igd_gfx_passthru;
> +
> +bool xen_igd_gfx_pt_enabled(void)
> +{
> +    return has_igd_gfx_passthru;
> +}
> +
> +void xen_igd_gfx_pt_set(bool value, Error **errp)
> +{
> +    has_igd_gfx_passthru = value;
> +}
> 
>  #define XEN_PT_NR_IRQS (256)
>  static uint8_t xen_pt_mapped_machine_irq[XEN_PT_NR_IRQS] = {0};
> diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
> index 179775db7b22..6e9cec95f3b7 100644
> --- a/hw/xen/xen_pt.h
> +++ b/hw/xen/xen_pt.h
> @@ -5,6 +5,9 @@
>  #include "hw/pci/pci.h"
>  #include "xen-host-pci-device.h"
> 
> +bool xen_igd_gfx_pt_enabled(void);
> +void xen_igd_gfx_pt_set(bool value, Error **errp);
> +
>  void xen_pt_log(const PCIDevice *d, const char *f, ...) GCC_FMT_ATTR(2, 3);
> 
>  #define XEN_PT_ERR(d, _f, _a...) xen_pt_log(d, "%s: Error: "_f, __func__, 
> ##_a)
> @@ -322,10 +325,9 @@ extern void *pci_assign_dev_load_option_rom(PCIDevice 
> *dev,
>                                              unsigned int domain,
>                                              unsigned int bus, unsigned int 
> slot,
>                                              unsigned int function);
> -extern bool has_igd_gfx_passthru;
>  static inline bool is_igd_vga_passthrough(XenHostPCIDevice *dev)
>  {
> -    return (has_igd_gfx_passthru
> +    return (xen_igd_gfx_pt_enabled()
>              && ((dev->class_code >> 0x8) == PCI_CLASS_DISPLAY_VGA));
>  }
>  int xen_pt_register_vga_regions(XenHostPCIDevice *dev);
> diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
> index 6a9e3135e8f9..564527e00997 100644
> --- a/stubs/Makefile.objs
> +++ b/stubs/Makefile.objs
> @@ -40,6 +40,7 @@ stub-obj-y += target-get-monitor-def.o
>  stub-obj-y += vmgenid.o
>  stub-obj-y += xen-common.o
>  stub-obj-y += xen-hvm.o
> +stub-obj-y += xen-pt.o
>  stub-obj-y += pci-host-piix.o
>  stub-obj-y += ram-block.o
>  stub-obj-y += ramfb.o
> diff --git a/stubs/xen-pt.c b/stubs/xen-pt.c
> new file mode 100644
> index 000000000000..2d8cac8d54b9
> --- /dev/null
> +++ b/stubs/xen-pt.c
> @@ -0,0 +1,22 @@
> +/*
> + * Copyright (C) 2020       Citrix Systems UK Ltd.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/xen/xen_pt.h"
> +#include "qapi/error.h"
> +
> +bool xen_igd_gfx_pt_enabled(void)
> +{
> +    return false;
> +}
> +
> +void xen_igd_gfx_pt_set(bool value, Error **errp)
> +{
> +    if (value) {
> +        error_setg(errp, "Xen PCI passthrough support not built in");
> +    }
> +}
> --
> Anthony PERARD