Re: [Qemu-devel] [PULL 02/22] pcie: check that slt ctrl changed before deleting

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 2 Jul 2019 at 16:06, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> During boot, linux would sometimes overwrites control of a powered off
> slot before powering it on. Unfortunately QEMU interprets that as a
> power off request and ejects the device.
>
> For example:
>
> /x86_64-softmmu/qemu-system-x86_64 -enable-kvm -S -machine q35  \
>     -device pcie-root-port,id=pcie_root_port_0,slot=2,chassis=2,addr=0x2,bus=pcie.0 \
>     -monitor stdio disk.qcow2
> (qemu)device_add virtio-balloon-pci,id=balloon,bus=pcie_root_port_0
> (qemu)cont
>
> Balloon is deleted during guest boot.
>
> To fix, save control beforehand and check that power
> or led state actually change before ejecting.
>
> Note: this is more a hack than a solution, ideally we'd
> find a better way to detect ejects, or move away
> from ejects completely and instead monitor whether
> it's safe to delete device due to e.g. its power state.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> Tested-by: Igor Mammedov <imammedo@redhat.com>

Hi; Coverity points out (CID 1403007) that...

> diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
> index e30334d74d..8d90c0e193 100644
> --- a/include/hw/pci/pcie.h
> +++ b/include/hw/pci/pcie.h
> @@ -107,7 +107,8 @@ void pcie_cap_lnkctl_reset(PCIDevice *dev);
>
>  void pcie_cap_slot_init(PCIDevice *dev, uint16_t slot);
>  void pcie_cap_slot_reset(PCIDevice *dev);
> -void pcie_cap_slot_write_config(PCIDevice *dev,
> +void pcie_cap_slot_get(PCIDevice *dev, uint16_t *slot_ctl, uint16_t *slt_sta);

...in the declaration of pci_cap_slot_get() the last 2
arguments are slot_ctl then slt_sta...

> --- a/hw/pci-bridge/pcie_root_port.c
> +++ b/hw/pci-bridge/pcie_root_port.c
> @@ -31,10 +31,13 @@ static void rp_write_config(PCIDevice *d, uint32_t address,
>  {
>      uint32_t root_cmd =
>          pci_get_long(d->config + d->exp.aer_cap + PCI_ERR_ROOT_COMMAND);
> +    uint16_t slt_ctl, slt_sta;
> +
> +    pcie_cap_slot_get(d, &slt_ctl, &slt_sta);

...which is the order we use here...

>
>      pci_bridge_write_config(d, address, val, len);
>      rp_aer_vector_update(d);
> -    pcie_cap_slot_write_config(d, address, val, len);
> +    pcie_cap_slot_write_config(d, slt_ctl, slt_sta, address, val, len);
>      pcie_aer_write_config(d, address, val, len);
>      pcie_aer_root_write_config(d, address, val, len, root_cmd);
>  }
> diff --git a/hw/pci-bridge/xio3130_downstream.c b/hw/pci-bridge/xio3130_downstream.c
> index 264e37d6a6..899b0fd6c9 100644
> --- a/hw/pci-bridge/xio3130_downstream.c
> +++ b/hw/pci-bridge/xio3130_downstream.c
> @@ -41,9 +41,12 @@
>  static void xio3130_downstream_write_config(PCIDevice *d, uint32_t address,
>                                           uint32_t val, int len)
>  {
> +    uint16_t slt_ctl, slt_sta;
> +
> +    pcie_cap_slot_get(d, &slt_sta, &slt_ctl);

...but in this callsite we pass slt_sta, slt_ctl.

Presumably this is a bug?

Also, but more trivially, the function declarations for
pci_cap_slot_get and pci_cap_slot_write_config call the argument
"slot_ctl", but the function definitions and all the call
sites drop the 'o' and call it "slt_ctl". Could we be consistent?

thanks
-- PMM