Re: [PATCH v5] xen: fix build without pci passthrough

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Thu, Jun 04, 2020 at 02:31:41PM -0400, Paolo Bonzini wrote:
> From: Anthony PERARD <anthony.perard@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>
> Message-Id: <20200603160442.3151170-1-anthony.perard@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Hi Paul,

Can I backport this patch to qemu-xen-4.14? It allows to build qemu
without pci passthrough support which seems to be important for FreeBSD
as PT with QEMU is only available on Linux.

(There's a fix to the patch that I would backport as well. "xen:
Actually fix build without passthrough")

Thanks.

> ---
>  accel/xen/xen-all.c  |  4 ++--
>  hw/Makefile.objs     |  2 +-
>  hw/i386/pc_piix.c    |  2 +-
>  hw/xen/Makefile.objs |  3 ++-
>  hw/xen/xen_pt.c      | 12 +++++++++++-
>  hw/xen/xen_pt.h      |  6 ++++--
>  hw/xen/xen_pt_stub.c | 22 ++++++++++++++++++++++
>  7 files changed, 43 insertions(+), 8 deletions(-)
>  create mode 100644 hw/xen/xen_pt_stub.c
> 
> diff --git a/accel/xen/xen-all.c b/accel/xen/xen-all.c
> index f3edc65ec9..0c24d4b191 100644
> --- a/accel/xen/xen-all.c
> +++ b/accel/xen/xen-all.c
> @@ -137,12 +137,12 @@ 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/Makefile.objs b/hw/Makefile.objs
> index 660e2b4373..4cbe5e4e57 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -35,7 +35,7 @@ devices-dirs-y += usb/
>  devices-dirs-$(CONFIG_VFIO) += vfio/
>  devices-dirs-y += virtio/
>  devices-dirs-y += watchdog/
> -devices-dirs-y += xen/
> +devices-dirs-$(CONFIG_XEN) += xen/
>  devices-dirs-$(CONFIG_MEM_DEVICE) += mem/
>  devices-dirs-$(CONFIG_NUBUS) += nubus/
>  devices-dirs-y += semihosting/
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index eea964e72b..054d3aa9f7 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -377,7 +377,7 @@ 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/Makefile.objs b/hw/xen/Makefile.objs
> index 340b2c5096..3fc715e595 100644
> --- a/hw/xen/Makefile.objs
> +++ b/hw/xen/Makefile.objs
> @@ -1,6 +1,7 @@
>  # xen backend driver support
> -common-obj-$(CONFIG_XEN) += xen-legacy-backend.o xen_devconfig.o xen_pvdev.o 
> xen-bus.o xen-bus-helper.o xen-backend.o
> +common-obj-y += xen-legacy-backend.o xen_devconfig.o xen_pvdev.o xen-bus.o 
> xen-bus-helper.o xen-backend.o
>  
>  obj-$(CONFIG_XEN_PCI_PASSTHROUGH) += xen-host-pci-device.o
>  obj-$(CONFIG_XEN_PCI_PASSTHROUGH) += xen_pt.o xen_pt_config_init.o 
> xen_pt_graphics.o xen_pt_msi.o
>  obj-$(CONFIG_XEN_PCI_PASSTHROUGH) += xen_pt_load_rom.o
> +obj-$(call $(lnot, $(CONFIG_XEN_PCI_PASSTHROUGH))) += xen_pt_stub.o
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index 81d5ad8da7..ab84443d5e 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 179775db7b..6e9cec95f3 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/hw/xen/xen_pt_stub.c b/hw/xen/xen_pt_stub.c
> new file mode 100644
> index 0000000000..2d8cac8d54
> --- /dev/null
> +++ b/hw/xen/xen_pt_stub.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");
> +    }
> +}
> -- 
> 2.26.2
> 
> 

-- 
Anthony PERARD