Re: [Qemu-devel] [PATCH v2 1/2] pcie: Add a simple PCIe ACS (Access Control Services) helper function

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 24 Jan 2019 11:12:52 +0100
Knut Omang <knut.omang@oracle.com> wrote:

> Add a helper function to add PCIe capability for Access Control Services (ACS)
> ACS support in the associated root port is a prerequisite to be able to do
> passthrough of individual functions of a device with VFIO
> without Alex Williamson's pcie_acs_override kernel patch or similar
> in the guest.
> 
> Signed-off-by: Knut Omang <knut.omang@oracle.com>
> ---
>  hw/pci/pcie.c              | 21 +++++++++++++++++++++
>  include/hw/pci/pcie.h      |  6 ++++++
>  include/hw/pci/pcie_regs.h |  4 ++++
>  3 files changed, 31 insertions(+)
> 
> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> index 230478f..5ab3d1d 100644
> --- a/hw/pci/pcie.c
> +++ b/hw/pci/pcie.c
> @@ -742,6 +742,13 @@ bool pcie_cap_is_arifwd_enabled(const PCIDevice *dev)
>          PCI_EXP_DEVCTL2_ARI;
>  }
>  
> +/* Access Control Services (ACS)
> + */

Comment style

> +void pcie_cap_acs_reset(PCIDevice *dev)
> +{
> +    pci_set_word(dev->config + dev->exp.acs_cap + PCI_ACS_CTRL, 0);
> +}
> +
>  /**************************************************************************
>   * pci express extended capability list management functions
>   * uint16_t ext_cap_id (16 bit)
> @@ -906,3 +913,17 @@ void pcie_ats_init(PCIDevice *dev, uint16_t offset)
>  
>      pci_set_word(dev->wmask + dev->exp.ats_cap + PCI_ATS_CTRL, 0x800f);
>  }
> +
> +/* ACS (Access Control Services) */
> +void pcie_acs_init(PCIDevice *dev, uint16_t offset)
> +{
> +    pcie_add_capability(dev, PCI_EXT_CAP_ID_ACS, PCI_ACS_VER,
> +                        offset, PCI_ACS_SIZEOF);
> +    dev->exp.acs_cap = offset;
> +    pci_set_word(dev->config + offset + PCI_ACS_CAP,
> +                 PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);

This is still only valid for downstream ports yet neither restricted
nor commented do indicate that.  You could use an object_dynamic_cast
to triggger an assert should someone use it for an invalid type of
device, ex:

assert(object_dynamic_cast(OBJECT(dev), TYPE_PCIE_SLOT));

> +
> +    pci_set_word(dev->config + offset + PCI_ACS_CTRL, 0);

Suspect this is unnecessary given the reset callback.

> +    pci_set_word(dev->wmask + offset + PCI_ACS_CTRL,
> +                 PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);
> +}
> diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
> index 5b82a0d..4c40711 100644
> --- a/include/hw/pci/pcie.h
> +++ b/include/hw/pci/pcie.h
> @@ -79,6 +79,9 @@ struct PCIExpressDevice {
>  
>      /* Offset of ATS capability in config space */
>      uint16_t ats_cap;
> +
> +    /* ACS */
> +    uint16_t acs_cap;
>  };
>  
>  #define COMPAT_PROP_PCP "power_controller_present"
> @@ -116,6 +119,8 @@ void pcie_cap_flr_init(PCIDevice *dev);
>  void pcie_cap_flr_write_config(PCIDevice *dev,
>                             uint32_t addr, uint32_t val, int len);
>  
> +void pcie_cap_acs_reset(PCIDevice *dev);
> +
>  /* ARI forwarding capability and control */
>  void pcie_cap_arifwd_init(PCIDevice *dev);
>  void pcie_cap_arifwd_reset(PCIDevice *dev);
> @@ -129,6 +134,7 @@ void pcie_add_capability(PCIDevice *dev,
>  void pcie_sync_bridge_lnk(PCIDevice *dev);
>  
>  void pcie_ari_init(PCIDevice *dev, uint16_t offset, uint16_t nextfn);
> +void pcie_acs_init(PCIDevice *dev, uint16_t offset);
>  void pcie_dev_ser_num_init(PCIDevice *dev, uint16_t offset, uint64_t ser_num);
>  void pcie_ats_init(PCIDevice *dev, uint16_t offset);
>  
> diff --git a/include/hw/pci/pcie_regs.h b/include/hw/pci/pcie_regs.h
> index ad4e780..3fc9aca 100644
> --- a/include/hw/pci/pcie_regs.h
> +++ b/include/hw/pci/pcie_regs.h
> @@ -175,4 +175,8 @@ typedef enum PCIExpLinkWidth {
>                                           PCI_ERR_COR_INTERNAL |         \
>                                           PCI_ERR_COR_HL_OVERFLOW)
>  
> +/* ACS */
> +#define PCI_ACS_VER                     0x2

There's no such version, even the PCIe 5.0 drafts only define version 1.

> +#define PCI_ACS_SIZEOF                  8
> +
>  #endif /* QEMU_PCIE_REGS_H */