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

[Laurent Vivier]

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?

Thanks,
Laurent