Re: [Qemu-devel] [PATCH 4/3] pcie: minor cleanups for slot control/status

[Christophe de Dinechin <dinechin@redhat.com>]

Michael S. Tsirkin writes:

> Rename function arguments to make intent clearer.
> Better documentation for slot control logic.
>
> Suggested-by: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
>
>  include/hw/pci/pcie.h |  3 ++-
>  hw/pci/pcie.c         | 17 +++++++++++------
>  2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
> index 8d90c0e193..34f277735c 100644
> --- a/include/hw/pci/pcie.h
> +++ b/include/hw/pci/pcie.h
> @@ -108,7 +108,8 @@ 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_get(PCIDevice *dev, uint16_t *slot_ctl, uint16_t *slt_sta);
> -void pcie_cap_slot_write_config(PCIDevice *dev, uint16_t slot_ctl, uint16_t slt_sta,
> +void pcie_cap_slot_write_config(PCIDevice *dev,
> +                                uint16_t old_slot_ctl, uint16_t old_slt_sta,
>                                  uint32_t addr, uint32_t val, int len);
>  int pcie_cap_slot_post_load(void *opaque, int version_id);
>  void pcie_cap_slot_push_attention_button(PCIDevice *dev);
> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> index c605d32dd4..a6beb567bd 100644
> --- a/hw/pci/pcie.c
> +++ b/hw/pci/pcie.c
> @@ -602,7 +602,8 @@ void pcie_cap_slot_get(PCIDevice *dev, uint16_t *slt_ctl, uint16_t *slt_sta)
>      *slt_sta = pci_get_word(exp_cap + PCI_EXP_SLTSTA);
>  }
>
> -void pcie_cap_slot_write_config(PCIDevice *dev, uint16_t slt_ctl, uint16_t slt_sta,
> +void pcie_cap_slot_write_config(PCIDevice *dev,
> +                                uint16_t old_slt_ctl, uint16_t old_slt_sta,
>                                  uint32_t addr, uint32_t val, int len)
>  {
>      uint32_t pos = dev->exp.exp_cap;
> @@ -625,8 +626,8 @@ void pcie_cap_slot_write_config(PCIDevice *dev, uint16_t slt_ctl, uint16_t slt_s
>                            PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_PDC | \
>                            PCI_EXP_SLTSTA_CC)
>
> -        if (val & ~slt_sta & PCIE_SLOT_EVENTS) {
> -            sltsta = (sltsta & ~PCIE_SLOT_EVENTS) | (slt_sta & PCIE_SLOT_EVENTS);
> +        if (val & ~old_slt_sta & PCIE_SLOT_EVENTS) {
> +            sltsta = (sltsta & ~PCIE_SLOT_EVENTS) | (old_slt_sta & PCIE_SLOT_EVENTS);
>              pci_set_word(exp_cap + PCI_EXP_SLTSTA, sltsta);
>          }
>          hotplug_event_clear(dev);
> @@ -646,13 +647,17 @@ void pcie_cap_slot_write_config(PCIDevice *dev, uint16_t slt_ctl, uint16_t slt_s
>      }
>
>      /*
> -     * If the slot is polulated, power indicator is off and power
> +     * If the slot is populated, power indicator is off and power
>       * controller is off, it is safe to detach the devices.
> +     *
> +     * Note: don't detach if condition was already true:
> +     * this is a work around for guests that overwrite
> +     * control of powered off slots before powering them on.
>       */
>      if ((sltsta & PCI_EXP_SLTSTA_PDS) && (val & PCI_EXP_SLTCTL_PCC) &&
>          (val & PCI_EXP_SLTCTL_PIC_OFF) == PCI_EXP_SLTCTL_PIC_OFF &&
> -        (!(slt_ctl & PCI_EXP_SLTCTL_PCC) ||
> -        (slt_ctl & PCI_EXP_SLTCTL_PIC_OFF) != PCI_EXP_SLTCTL_PIC_OFF)) {
> +        (!(old_slt_ctl & PCI_EXP_SLTCTL_PCC) ||
> +        (old_slt_ctl & PCI_EXP_SLTCTL_PIC_OFF) != PCI_EXP_SLTCTL_PIC_OFF)) {
>          PCIBus *sec_bus = pci_bridge_get_sec_bus(PCI_BRIDGE(dev));
>          pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
>                              pcie_unplug_device, NULL);

Good idea.
Reviewed-by: Christophe de Dinechin <dinechin@redhat.com>

--
Cheers,
Christophe de Dinechin (IRC c3d)