Re: [PATCH 6.0 20/20] fbdev/core: Remove remove_conflicting_pci_framebuffers()

[Boris V.]

On 01/11/2022 11:34, Thomas Zimmermann wrote:
> (cc: Alex Williamson)
>
> Hi
>
> Am 01.11.22 um 09:42 schrieb Boris V.:
> > On 24/10/2022 13:31, Greg Kroah-Hartman wrote:
> > > From: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > >
> > > commit 9d69ef1838150c7d87afc1a87aa658c637217585 upstream.
> > >
> > > Remove remove_conflicting_pci_framebuffers() and implement similar
> > > functionality in aperture_remove_conflicting_pci_device(), which was
> > > the only caller. Removes an otherwise unused interface and streamlines
> > > the aperture helper. No functional changes.
> > >
> > > Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > > Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> > > Link: 
> > > https://patchwork.freedesktop.org/patch/msgid/20220718072322.8927-5-tzimmermann@xxxxxxx
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/video/aperture.c         |   30 ++++++++++++++----------
> > >   drivers/video/fbdev/core/fbmem.c |   48 
> > > ---------------------------------------
> > >   include/linux/fb.h               |    2 -
> > >   3 files changed, 18 insertions(+), 62 deletions(-)
> > >
> > > --- a/drivers/video/aperture.c
> > > +++ b/drivers/video/aperture.c
> > > @@ -335,30 +335,36 @@ EXPORT_SYMBOL(aperture_remove_conflictin
> > >    */
> > >   int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, 
> > > const char *name)
> > >   {
> > > +    bool primary = false;
> > >       resource_size_t base, size;
> > >       int bar, ret;
> > > -    /*
> > > -     * WARNING: Apparently we must kick fbdev drivers before vgacon,
> > > -     * otherwise the vga fbdev driver falls over.
> > > -     */
> > > -#if IS_REACHABLE(CONFIG_FB)
> > > -    ret = remove_conflicting_pci_framebuffers(pdev, name);
> > > -    if (ret)
> > > -        return ret;
> > > +#ifdef CONFIG_X86
> > > +    primary = pdev->resource[PCI_ROM_RESOURCE].flags & 
> > > IORESOURCE_ROM_SHADOW;
> > >   #endif
> > > -    ret = vga_remove_vgacon(pdev);
> > > -    if (ret)
> > > -        return ret;
> > >       for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
> > >           if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
> > >               continue;
> > > +
> > >           base = pci_resource_start(pdev, bar);
> > >           size = pci_resource_len(pdev, bar);
> > > -        aperture_detach_devices(base, size);
> > > +        ret = aperture_remove_conflicting_devices(base, size, 
> > > primary, name);
> > > +        if (ret)
> > > +            break;
> > >       }
> > > +    if (ret)
> > > +        return ret;
> > > +
> > > +    /*
> > > +     * WARNING: Apparently we must kick fbdev drivers before vgacon,
> > > +     * otherwise the vga fbdev driver falls over.
> > > +     */
> > > +    ret = vga_remove_vgacon(pdev);
> > > +    if (ret)
> > > +        return ret;
> > > +
> > >       return 0;
> > >   }
> > > --- a/drivers/video/fbdev/core/fbmem.c
> > > +++ b/drivers/video/fbdev/core/fbmem.c
> > > @@ -1788,54 +1788,6 @@ int remove_conflicting_framebuffers(stru
> > >   EXPORT_SYMBOL(remove_conflicting_framebuffers);
> > >   /**
> > > - * remove_conflicting_pci_framebuffers - remove firmware-configured 
> > > framebuffers for PCI devices
> > > - * @pdev: PCI device
> > > - * @name: requesting driver name
> > > - *
> > > - * This function removes framebuffer devices (eg. initialized by 
> > > firmware)
> > > - * using memory range configured for any of @pdev's memory bars.
> > > - *
> > > - * The function assumes that PCI device with shadowed ROM drives a 
> > > primary
> > > - * display and so kicks out vga16fb.
> > > - */
> > > -int remove_conflicting_pci_framebuffers(struct pci_dev *pdev, const 
> > > char *name)
> > > -{
> > > -    struct apertures_struct *ap;
> > > -    bool primary = false;
> > > -    int err, idx, bar;
> > > -
> > > -    for (idx = 0, bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> > > -        if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
> > > -            continue;
> > > -        idx++;
> > > -    }
> > > -
> > > -    ap = alloc_apertures(idx);
> > > -    if (!ap)
> > > -        return -ENOMEM;
> > > -
> > > -    for (idx = 0, bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> > > -        if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
> > > -            continue;
> > > -        ap->ranges[idx].base = pci_resource_start(pdev, bar);
> > > -        ap->ranges[idx].size = pci_resource_len(pdev, bar);
> > > -        pci_dbg(pdev, "%s: bar %d: 0x%lx -> 0x%lx\n", __func__, bar,
> > > -            (unsigned long)pci_resource_start(pdev, bar),
> > > -            (unsigned long)pci_resource_end(pdev, bar));
> > > -        idx++;
> > > -    }
> > > -
> > > -#ifdef CONFIG_X86
> > > -    primary = pdev->resource[PCI_ROM_RESOURCE].flags &
> > > -                    IORESOURCE_ROM_SHADOW;
> > > -#endif
> > > -    err = remove_conflicting_framebuffers(ap, name, primary);
> > > -    kfree(ap);
> > > -    return err;
> > > -}
> > > -EXPORT_SYMBOL(remove_conflicting_pci_framebuffers);
> > > -
> > > -/**
> > >    *    register_framebuffer - registers a frame buffer device
> > >    *    @fb_info: frame buffer info structure
> > >    *
> > > --- a/include/linux/fb.h
> > > +++ b/include/linux/fb.h
> > > @@ -615,8 +615,6 @@ extern ssize_t fb_sys_write(struct fb_in
> > >   /* drivers/video/fbmem.c */
> > >   extern int register_framebuffer(struct fb_info *fb_info);
> > >   extern void unregister_framebuffer(struct fb_info *fb_info);
> > > -extern int remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
> > > -                           const char *name);
> > >   extern int remove_conflicting_framebuffers(struct apertures_struct 
> > > *a,
> > >                          const char *name, bool primary);
> > >   extern int fb_prepare_logo(struct fb_info *fb_info, int rotate);
> >
> > Hello,
> >
> > this patch seems to disable console/framebuffer when vfio-pci is used.
> > I hava 2 nvidia GPUs one is used for host and other is passed through 
> > to VM.
>
> Vfio uses this helper to unload the driver before passing it to a VM 
> AFAIU. But unless you're using nouveau, you're on your own.
>
> Best regards
> Thomas

But this happens at boot, when vfio-pci module is loaded. Not when VM is 
started.
And console/framebuffer is unloaded for primary/boot GPU, not the one 
passed to VM.
Also no GPU driver is loaded at this point. And there was no problem 
before, it stopped working with 6.0.4 kernel.