Re: [PATCH v4 3/3] hw/vfio: add ramfb migration support

["Cédric Le Goater" <clg@redhat.com>]

On 10/5/23 13:30, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Add a "VFIODisplay" subsection whenever "x-ramfb-migrate" is turned on.
> 
> Turn it off by default on machines <= 8.1 for compatibility reasons.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   hw/vfio/pci.h     |  3 +++
>   hw/core/machine.c |  1 +
>   hw/vfio/display.c | 20 ++++++++++++++++++++
>   hw/vfio/pci.c     | 44 ++++++++++++++++++++++++++++++++++++++++++++
>   stubs/ramfb.c     |  2 ++
>   5 files changed, 70 insertions(+)
> 
> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> index 2d836093a8..fd06695542 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -173,6 +173,7 @@ struct VFIOPCIDevice {
>       bool no_kvm_ioeventfd;
>       bool no_vfio_ioeventfd;
>       bool enable_ramfb;
> +    OnOffAuto ramfb_migrate;
>       bool defer_kvm_irq_routing;
>       bool clear_parent_atomics_on_exit;
>       VFIODisplay *dpy;
> @@ -226,4 +227,6 @@ void vfio_display_reset(VFIOPCIDevice *vdev);
>   int vfio_display_probe(VFIOPCIDevice *vdev, Error **errp);
>   void vfio_display_finalize(VFIOPCIDevice *vdev);
>   
> +extern const VMStateDescription vfio_display_vmstate;
> +
>   #endif /* HW_VFIO_VFIO_PCI_H */
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index e4361e3d48..f2c59a293c 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -33,6 +33,7 @@
>   
>   GlobalProperty hw_compat_8_1[] = {
>       { "ramfb", "x-migrate", "off" },
> +    { "vfio-pci-nohotplug", "x-ramfb-migrate", "off" }
>   };
>   const size_t hw_compat_8_1_len = G_N_ELEMENTS(hw_compat_8_1);
>   
> diff --git a/hw/vfio/display.c b/hw/vfio/display.c
> index bec864f482..0bdb807642 100644
> --- a/hw/vfio/display.c
> +++ b/hw/vfio/display.c
> @@ -542,3 +542,23 @@ void vfio_display_finalize(VFIOPCIDevice *vdev)
>       vfio_display_edid_exit(vdev->dpy);
>       g_free(vdev->dpy);
>   }
> +
> +static bool migrate_needed(void *opaque)
> +{
> +    VFIODisplay *dpy = opaque;
> +    bool ramfb_exists = dpy->ramfb != NULL;
> +
> +    /* see vfio_display_migration_needed() */
> +    assert(ramfb_exists);
> +    return ramfb_exists;
> +}
> +
> +const VMStateDescription vfio_display_vmstate = {
> +    .name = "VFIODisplay",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = migrate_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_STRUCT_POINTER(ramfb, VFIODisplay, ramfb_vmstate, RAMFBState),
> +    }
> +};
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 3b2ca3c24c..d2ede2f1a2 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2608,6 +2608,32 @@ static bool vfio_msix_present(void *opaque, int version_id)
>       return msix_present(pdev);
>   }
>   
> +static bool vfio_display_migration_needed(void *opaque)
> +{
> +    VFIOPCIDevice *vdev = opaque;
> +
> +    /*
> +     * We need to migrate the VFIODisplay object if ramfb *migration* was
> +     * explicitly requested (in which case we enforced both ramfb=on and
> +     * display=on), or ramfb migration was left at the default "auto"
> +     * setting, and *ramfb* was explicitly requested (in which case we
> +     * enforced display=on).
> +     */
> +    return vdev->ramfb_migrate == ON_OFF_AUTO_ON ||
> +        (vdev->ramfb_migrate == ON_OFF_AUTO_AUTO && vdev->enable_ramfb);> +}
> +
> +const VMStateDescription vmstate_vfio_display = {
> +    .name = "VFIOPCIDevice/VFIODisplay",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = vfio_display_migration_needed,
> +    .fields = (VMStateField[]){
> +        VMSTATE_STRUCT_POINTER(dpy, VFIOPCIDevice, vfio_display_vmstate, VFIODisplay),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>   const VMStateDescription vmstate_vfio_pci_config = {
>       .name = "VFIOPCIDevice",
>       .version_id = 1,
> @@ -2616,6 +2642,10 @@ const VMStateDescription vmstate_vfio_pci_config = {
>           VMSTATE_PCI_DEVICE(pdev, VFIOPCIDevice),
>           VMSTATE_MSIX_TEST(pdev, VFIOPCIDevice, vfio_msix_present),
>           VMSTATE_END_OF_LIST()
> +    },
> +    .subsections = (const VMStateDescription*[]) {
> +        &vmstate_vfio_display,
> +        NULL
>       }
>   };
>   
> @@ -3271,6 +3301,19 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>           }
>       }
>   
> +    if (vdev->ramfb_migrate == ON_OFF_AUTO_ON && !vdev->enable_ramfb) {
> +        error_setg(errp, "x-ramfb-migrate requires ramfb=on");

This is a case where QEMU would be run from the command line. Could we
ouput a warning and force "ramfb_migrate" to OFF in that case ? since
the machine would still run.

Thanks,

C.


> +        goto out_deregister;
> +    }
> +    if (vbasedev->enable_migration == ON_OFF_AUTO_OFF) {
> +        if (vdev->ramfb_migrate == ON_OFF_AUTO_AUTO) {
> +            vdev->ramfb_migrate = ON_OFF_AUTO_OFF;
> +        } else if (vdev->ramfb_migrate == ON_OFF_AUTO_ON) {
> +            error_setg(errp, "x-ramfb-migrate requires enable-migration");
> +            goto out_deregister;
> +        }
> +    }
> +
>       if (!pdev->failover_pair_id) {
>           if (!vfio_migration_realize(vbasedev, errp)) {
>               goto out_deregister;
> @@ -3484,6 +3527,7 @@ static const TypeInfo vfio_pci_dev_info = {
>   
>   static Property vfio_pci_dev_nohotplug_properties[] = {
>       DEFINE_PROP_BOOL("ramfb", VFIOPCIDevice, enable_ramfb, false),
> +    DEFINE_PROP_ON_OFF_AUTO("x-ramfb-migrate", VFIOPCIDevice, ramfb_migrate, ON_OFF_AUTO_AUTO),
>       DEFINE_PROP_END_OF_LIST(),
>   };
>   
> diff --git a/stubs/ramfb.c b/stubs/ramfb.c
> index 48143f3354..cf64733b10 100644
> --- a/stubs/ramfb.c
> +++ b/stubs/ramfb.c
> @@ -2,6 +2,8 @@
>   #include "qapi/error.h"
>   #include "hw/display/ramfb.h"
>   
> +const VMStateDescription ramfb_vmstate = {};
> +
>   void ramfb_display_update(QemuConsole *con, RAMFBState *s)
>   {
>   }