linux-kernel - Re: [PATCH] pci: acpiphp: try to reassign resources on bridge if necessary

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Message-ID: <CAJZ5v0gWKwOiACmK9=ru5W15Kydv6JqKJ8d4ngzKC7jqAjjcpQ@mail.gmail.com>
Date:   Tue, 18 Apr 2023 17:38:15 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Igor Mammedov <imammedo@...hat.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, mst@...hat.com, lenb@...nel.org,
        bhelgaas@...gle.com, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: acpiphp: try to reassign resources on bridge if necessary

On Tue, Apr 18, 2023 at 4:17 PM Igor Mammedov <imammedo@...hat.com> wrote:
>
> On Tue, 18 Apr 2023 14:55:29 +0200
> "Rafael J. Wysocki" <rafael@...nel.org> wrote:
>
> > On Tue, Apr 18, 2023 at 10:50 AM Igor Mammedov <imammedo@...hat.com> wrote:
> > >
> > > When using ACPI PCI hotplug, hotplugging a device with
> > > large BARs may fail if bridge windows programmed by
> > > firmware are not large enough.
> > >
> > > Reproducer:
> > >   $ qemu-kvm -monitor stdio -M q35  -m 4G \
> > >       -global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=on \
> > >       -device id=rp1,pcie-root-port,bus=pcie.0,chassis=4 \
> > >       disk_image
> > >
> > >  wait till linux guest boots, then hotplug device
> > >    (qemu) device_add qxl,bus=rp1
> > >
> > >  hotplug on guest side fails with:
> > >    pci 0000:01:00.0: [1b36:0100] type 00 class 0x038000
> > >    pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x03ffffff]
> > >    pci 0000:01:00.0: reg 0x14: [mem 0x00000000-0x03ffffff]
> > >    pci 0000:01:00.0: reg 0x18: [mem 0x00000000-0x00001fff]
> > >    pci 0000:01:00.0: reg 0x1c: [io  0x0000-0x001f]
> > >    pci 0000:01:00.0: BAR 0: no space for [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 0: failed to assign [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 1: no space for [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 1: failed to assign [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 2: assigned [mem 0xfe800000-0xfe801fff]
> > >    pci 0000:01:00.0: BAR 3: assigned [io  0x1000-0x101f]
> > >    qxl 0000:01:00.0: enabling device (0000 -> 0003)
> > >    Unable to create vram_mapping
> > >    qxl: probe of 0000:01:00.0 failed with error -12
> > >
> > > However when using native PCIe hotplug
> > >   '-global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off'
> > > it works fine, since kernel attempts to reassign unused resources.
> > > Use the same machinery as native PCIe hotplug to (re)assign resources.
> > >
> > > Signed-off-by: Igor Mammedov <imammedo@...hat.com>
> >
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > or please let me know if you want me to pick this up.
>
> It would be nice if you could pick it up.

OK, I'll do that unless Bjorn tells me that he prefers to take it via
the PCI tree.

Thanks!

> >
> > > ---
> > > tested in QEMU with Q35 machine on PCIE root port and also
> > > with nested conventional bridge attached to root port.
> > > ---
> > >  drivers/pci/hotplug/acpiphp_glue.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> > > index 5b1f271c6034..9aebde28a92f 100644
> > > --- a/drivers/pci/hotplug/acpiphp_glue.c
> > > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> > > @@ -517,7 +517,7 @@ static void enable_slot(struct acpiphp_slot *slot, bool bridge)
> > >                                 }
> > >                         }
> > >                 }
> > > -               __pci_bus_assign_resources(bus, &add_list, NULL);
> > > +               pci_assign_unassigned_bridge_resources(bus->self);
> > >         }
> > >
> > >         acpiphp_sanitize_bus(bus);
> > > --
> > > 2.39.1
> > >
> >
>