Re: [PATCH v5 3/3] hw/vfio: add ramfb migration support

[Marc-André Lureau]

Hi

On Tue, Oct 10, 2023 at 11:03 AM Cédric Le Goater <clg@redhat.com> wrote:
>
> On 10/9/23 12:19, Laszlo Ersek wrote:
> > On 10/9/23 08:32, 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>
> >> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> >> ---
> >>   hw/vfio/pci.h     |  3 +++
> >>   hw/core/machine.c |  1 +
> >>   hw/vfio/display.c | 21 +++++++++++++++++++++
> >>   hw/vfio/pci.c     | 44 ++++++++++++++++++++++++++++++++++++++++++++
> >>   stubs/ramfb.c     |  2 ++
> >>   5 files changed, 71 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 6305f2d7a4..05aef2cf9f 100644
> >> --- a/hw/core/machine.c
> >> +++ b/hw/core/machine.c
> >> @@ -35,6 +35,7 @@
> >>   GlobalProperty hw_compat_8_1[] = {
> >>       { TYPE_PCI_BRIDGE, "x-pci-express-writeable-slt-bug", "true" },
> >>       { "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..2739ba56ec 100644
> >> --- a/hw/vfio/display.c
> >> +++ b/hw/vfio/display.c
> >> @@ -542,3 +542,24 @@ 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),
> >> +        VMSTATE_END_OF_LIST(),
> >> +    }
> >> +};
> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> >> index 3b2ca3c24c..e44ed21180 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) {
> >> +        warn_report("x-ramfb-migrate=on but ramfb=off");
> >> +        vdev->ramfb_migrate = ON_OFF_AUTO_OFF;
> >
> > the warning could give a hint about the resultant action taken (i.e.,
> > forcing off x-ramfb-migrate), but don't repost just for that; it's a nit.
>
> yes.
>
> How about :
>
>          warn_report("x-ramfb-migrate=on but ramfb=off. Forcing 
> x-ramfb-migrate to off.");

Sure, that's better.

>
> I can amend the patch if you agree.

 thanks!