Re: [PULL v3 05/19] hw/acpi/ich9: Set ACPI PCI hot-plug as default on Q35

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 21, 2021 at 06:27:33PM +0200, Igor Mammedov wrote:
> On Wed, 21 Jul 2021 12:09:01 -0400
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Wed, Jul 21, 2021 at 05:49:16PM +0200, Laurent Vivier wrote:
> > > On 21/07/2021 16:59, Igor Mammedov wrote:  
> > > > On Tue, 20 Jul 2021 14:56:06 +0200
> > > > Laurent Vivier <lvivier@redhat.com> wrote:
> > > >   
> > > >> On 20/07/2021 13:38, Laurent Vivier wrote:  
> > > >>> On 16/07/2021 17:15, Michael S. Tsirkin wrote:    
> > > >>>> From: Julia Suvorova <jusual@redhat.com>
> > > >>>>
> > > >>>> Q35 has three different types of PCI devices hot-plug: PCIe Native,
> > > >>>> SHPC Native and ACPI hot-plug. This patch changes the default choice
> > > >>>> for cold-plugged bridges from PCIe Native to ACPI Hot-plug with
> > > >>>> ability to use SHPC and PCIe Native for hot-plugged bridges.
> > > >>>>
> > > >>>> This is a list of the PCIe Native hot-plug issues that led to this
> > > >>>> change:
> > > >>>>     * no racy behavior during boot (see 110c477c2ed)
> > > >>>>     * no delay during deleting - after the actual power off software
> > > >>>>       must wait at least 1 second before indicating about it. This case
> > > >>>>       is quite important for users, it even has its own bug:
> > > >>>>           https://bugzilla.redhat.com/show_bug.cgi?id=1594168
> > > >>>>     * no timer-based behavior - in addition to the previous example,
> > > >>>>       the attention button has a 5-second waiting period, during which
> > > >>>>       the operation can be canceled with a second press. While this
> > > >>>>       looks fine for manual button control, automation will result in
> > > >>>>       the need to queue or drop events, and the software receiving
> > > >>>>       events in all sort of unspecified combinations of attention/power
> > > >>>>       indicator states, which is racy and uppredictable.
> > > >>>>     * fixes:
> > > >>>>         * https://bugzilla.redhat.com/show_bug.cgi?id=1752465
> > > >>>>         * https://bugzilla.redhat.com/show_bug.cgi?id=1690256
> > > >>>>
> > > >>>> To return to PCIe Native hot-plug:
> > > >>>>     -global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off
> > > >>>>
> > > >>>> Known issue: older linux guests need the following flag
> > > >>>> to allow hotplugged pci express devices to use io:
> > > >>>>         -device pcie-root-port,io-reserve=4096.
> > > >>>> io is unusual for pci express so this seems minor.
> > > >>>> We'll fix this by a follow up patch.
> > > >>>>
> > > >>>> Signed-off-by: Julia Suvorova <jusual@redhat.com>
> > > >>>> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> > > >>>> Message-Id: <20210713004205.775386-6-jusual@redhat.com>
> > > >>>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > > >>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > >>>> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > > >>>> ---
> > > >>>>  hw/acpi/ich9.c | 2 +-
> > > >>>>  hw/i386/pc.c   | 1 +
> > > >>>>  2 files changed, 2 insertions(+), 1 deletion(-)
> > > >>>>
> > > >>>> diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
> > > >>>> index 2f4eb453ac..778e27b659 100644
> > > >>>> --- a/hw/acpi/ich9.c
> > > >>>> +++ b/hw/acpi/ich9.c
> > > >>>> @@ -427,7 +427,7 @@ void ich9_pm_add_properties(Object *obj, ICH9LPCPMRegs *pm)
> > > >>>>      pm->disable_s3 = 0;
> > > >>>>      pm->disable_s4 = 0;
> > > >>>>      pm->s4_val = 2;
> > > >>>> -    pm->use_acpi_hotplug_bridge = false;
> > > >>>> +    pm->use_acpi_hotplug_bridge = true;
> > > >>>>  
> > > >>>>      object_property_add_uint32_ptr(obj, ACPI_PM_PROP_PM_IO_BASE,
> > > >>>>                                     &pm->pm_io_base, OBJ_PROP_FLAG_READ);
> > > >>>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > > >>>> index aa79c5e0e6..f4c7a78362 100644
> > > >>>> --- a/hw/i386/pc.c
> > > >>>> +++ b/hw/i386/pc.c
> > > >>>> @@ -99,6 +99,7 @@ GlobalProperty pc_compat_6_0[] = {
> > > >>>>      { "qemu64" "-" TYPE_X86_CPU, "model", "6" },
> > > >>>>      { "qemu64" "-" TYPE_X86_CPU, "stepping", "3" },
> > > >>>>      { TYPE_X86_CPU, "x-vendor-cpuid-only", "off" },
> > > >>>> +    { "ICH9-LPC", "acpi-pci-hotplug-with-bridge-support", "off" },
> > > >>>>  };
> > > >>>>  const size_t pc_compat_6_0_len = G_N_ELEMENTS(pc_compat_6_0);
> > > >>>>  
> > > >>>>    
> > > >>>
> > > >>> There is an issue with this patch.
> > > >>>
> > > >>> When I try to unplug a VFIO device I have the following error and the device is not unplugged:
> > > >>>
> > > >>> (qemu) device_del hostdev0
> > > >>>
> > > >>> [   34.116714] ACPI BIOS Error (bug): Could not resolve symbol [^S0B.PCNT], AE_NOT_FOUND
> > > >>> (20201113/psargs-330)
> > > >>> [   34.117987] ACPI Error: Aborting method \_SB.PCI0.PCNT due to previous error
> > > >>> (AE_NOT_FOUND) (20201113/psparse-531)
> > > >>> [   34.119318] ACPI Error: Aborting method \_GPE._E01 due to previous error (AE_NOT_FOUND)
> > > >>> (20201113/psparse-531)
> > > >>> [   34.120600] ACPI Error: AE_NOT_FOUND, while evaluating GPE method [_E01]
> > > >>> (20201113/evgpe-515)
> > > >>>
> > > >>> We can see device is not unplugged (03:00.0)
> > > >>>
> > > >>> # lspci -v -s 03:00.0
> > > >>> 03:00.0 Ethernet controller: Intel Corporation Ethernet Virtual Function 700 Series (rev 02)
> > > >>> 	Subsystem: Intel Corporation Device 0000
> > > >>> 	Flags: bus master, fast devsel, latency 0
> > > >>> 	Memory at fe800000 (64-bit, prefetchable) [size=64K]
> > > >>> 	Memory at fe810000 (64-bit, prefetchable) [size=16K]
> > > >>> 	Capabilities: [70] MSI-X: Enable+ Count=5 Masked-
> > > >>> 	Capabilities: [a0] Express Endpoint, MSI 00
> > > >>> 	Capabilities: [100] Advanced Error Reporting
> > > >>> 	Capabilities: [1a0] Transaction Processing Hints
> > > >>> 	Capabilities: [1d0] Access Control Services
> > > >>> 	Kernel driver in use: iavf
> > > >>> 	Kernel modules: iavf
> > > >>>
> > > >>> My guest kernel is from RHEL 8.5 (4.18.0-310.el8.x86_64) and my command line is:
> > > >>>
> > > >>> $QEMU \
> > > >>> -L .../pc-bios \
> > > >>> -nodefaults \
> > > >>> -nographic \
> > > >>> -machine q35 \
> > > >>> -device pcie-root-port,id=pcie-root-port-0,multifunction=on,bus=pcie.0,addr=0x1,chassis=1 \
> > > >>> -device pcie-pci-bridge,id=pcie-pci-bridge-0,addr=0x0,bus=pcie-root-port-0  \
> > > >>> -device pcie-root-port,id=pcie-root-port-1,port=0x1,addr=0x1.0x1,bus=pcie.0,chassis=2 \
> > > >>> -device pcie-root-port,id=pcie-root-port-2,port=0x2,addr=0x1.0x2,bus=pcie.0,chassis=3 \
> > > >>> -device pcie-root-port,id=pcie-root-port-3,port=0x3,addr=0x1.0x3,bus=pcie.0,chassis=4 \
> > > >>> -device
> > > >>> pcie-root-port,id=pcie_extra_root_port_0,multifunction=on,bus=pcie.0,addr=0x3,chassis=5 \
> > > >>> -nodefaults \
> > > >>> -m 4066  \
> > > >>> -smp 4 \
> > > >>> -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pcie-root-port-2,addr=0x0 \
> > > >>> -blockdev
> > > >>> node-name=file_image1,driver=file,auto-read-only=on,discard=unmap,aio=threads,filename=$IMAGE,cache.direct=on,cache.no-fl\
> > > >>> -blockdev
> > > >>> node-name=drive_image1,driver=qcow2,read-only=off,cache.direct=on,cache.no-flush=off,file=file_image1
> > > >>> \
> > > >>> -device scsi-hd,id=image1,drive=drive_image1,write-cache=on \
> > > >>> -enable-kvm \
> > > >>> -serial mon:stdio \
> > > >>> -device vfio-pci,host=04:02.0,bus=pcie-root-port-1,addr=0x0,id=hostdev0
> > > >>>
> > > >>> PCI 04:02.0 is:
> > > >>>
> > > >>> $ lspci -v -s 04:02.0
> > > >>> 04:02.0 Ethernet controller: Intel Corporation Ethernet Virtual Function 700 Series (rev 02)
> > > >>> 	Subsystem: Intel Corporation Device 0000
> > > >>> 	Flags: fast devsel, NUMA node 0, IOMMU group 53
> > > >>> 	Memory at 92400000 (64-bit, prefetchable) [virtual] [size=64K]
> > > >>> 	Memory at 92910000 (64-bit, prefetchable) [virtual] [size=16K]
> > > >>> 	Capabilities: <access denied>
> > > >>> 	Kernel driver in use: vfio-pci
> > > >>> 	Kernel modules: iavf
> > > >>>
> > > >>> Any idea?    
> > > >>
> > > >> It also happens with non-VFIO device like e1000e:
> > > >>
> > > >> ...
> > > >> -device e1000e,bus=pcie-root-port-1,addr=0x0,id=hostdev0 \  
> > > >                      ^^^^^^^^^^^^^
> > > > ACPI hotplug operates on slot level, so functions greater than 0 are not considered,
> > > > hence unexpected ACPI error. For above CLI, setting 'addr' on root-ports to dedicated slots
> > > > should fix issue.
> > > >   
> > > 
> > > Thank you for your answer.
> > > 
> > > It works well with something like this:
> > > 
> > > ...
> > > -device pcie-root-port,id=pcie-root-port-0,addr=0x1,bus=pcie.0,chassis=1 \
> > > -device pcie-root-port,id=pcie-root-port-1,addr=0x2,bus=pcie.0,chassis=2 \
> > > -device pcie-root-port,id=pcie-root-port-2,addr=0x3,bus=pcie.0,chassis=3 \
> > > -device pcie-root-port,id=pcie-root-port-3,addr=0x4,bus=pcie.0,chassis=4 \
> > > -device e1000e,mac=52:54:00:12:34:56,id=hostdev0,bus=pcie-root-port-1 \
> > > ...
> > > 
> > > Is this what you meant?
> yep
> 
> > > 
> > > On an other hand, the previous configuration worked well before this patch, can we see
> > > that as a regression?
> 
> Maybe for 6.1 we should flip default back to native (revert 17858a16950860),
> until we sort out multifunction issues.

Revert had advantages and disadvantages as usual. Let's see what the fix
is, then we can decide.

> 
> > > 
> > > Thanks,
> > > Laurent  
> > 
> > 
> > I agree, port itself can be multifunction, slot behind it is a single
> > function. Looks like a bug to me. Julia?
> I quickly cobbled up acpi hack to do it.
> 
> But kernel refuses to see bridges described
> in ACPI other than on function 0.
> I'll play with it tomorrow some more.
> 
> PS:
> (it's a bit more than I'm comfortable to push as a fix for 6.1 anyways)