Re: [Qemu-devel] [PATCH v5 1/2] pcie: Add a simple PCIe ACS (Access Control Services) helper function

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

On Sat, 16 Feb 2019 17:51:11 +0100
Knut Omang <knut.omang@oracle.com> wrote:

> Implementing an ACS capability on downstream ports and multifunction
> endpoints indicates isolation and IOMMU visibility to a finer
> granularity. This creates smaller IOMMU groups in the guest and thus
> more flexibility in assigning endpoints to guest userspace or an L2
> guest.
> 
> Signed-off-by: Knut Omang <knut.omang@oracle.com>
> ---
>  hw/pci/pcie.c              | 39 +++++++++++++++++++++++++++++++++++++++-
>  include/hw/pci/pcie.h      |  6 ++++++-
>  include/hw/pci/pcie_regs.h |  4 ++++-
>  3 files changed, 49 insertions(+)
> 
> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> index 230478f..6afc37a 100644
> --- a/hw/pci/pcie.c
> +++ b/hw/pci/pcie.c
> @@ -906,3 +906,42 @@ 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)
> +{
> +    bool is_downstream = pci_is_express_downstream_port(dev);
> +    uint16_t cap_bits = 0;
> +
> +    /* For endpoints, only multifunction devs may have an ACS capability: */
> +    assert(is_downstream ||
> +           (dev->cap_present & QEMU_PCI_CAP_MULTIFUNCTION) ||
> +           PCI_FUNC(dev->devfn));
> +
> +    pcie_add_capability(dev, PCI_EXT_CAP_ID_ACS, PCI_ACS_VER, offset,
> +                        PCI_ACS_SIZEOF);
> +    dev->exp.acs_cap = offset;
> +
> +    if (is_downstream) {
> +        /* Downstream ports must implement SV, TB, RR, CR, and UF (with
> +         * caveats on the latter three that we ignore for simplicity).
> +         * Endpoints may also implement a subset of ACS capabilities,
> +         * but these are optional if the endpoint does not support
> +         * peer-to-peer between functions and thus omitted here.
> +         * Downstream switch ports must also implement DT, while this
> +         * is optional for root ports, so we set that as well:
> +         */

Again...
https://git.qemu.org/?p=qemu.git;a=blob;f=CODING_STYLE;hb=HEAD#l127

Personally I'd add DT in the original list rather than mention is
separately, the caveats are pretty similar.

> +        cap_bits = PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR |
> +            PCI_ACS_CR | PCI_ACS_UF | PCI_ACS_DT;
> +    }
> +
> +    pci_set_word(dev->config + offset + PCI_ACS_CAP, cap_bits);
> +    pci_set_word(dev->wmask + offset + PCI_ACS_CTRL, cap_bits);
> +}
> +
> +void pcie_acs_reset(PCIDevice *dev)
> +{
> +    if (dev->exp.acs_cap) {
> +        pci_set_word(dev->config + dev->exp.acs_cap + PCI_ACS_CTRL, 0);
> +    }
> +}
> diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
> index 5b82a0d..e30334d 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"
> @@ -128,6 +131,9 @@ void pcie_add_capability(PCIDevice *dev,
>                           uint16_t offset, uint16_t size);
>  void pcie_sync_bridge_lnk(PCIDevice *dev);
>  
> +void pcie_acs_init(PCIDevice *dev, uint16_t offset);
> +void pcie_acs_reset(PCIDevice *dev);
> +
>  void pcie_ari_init(PCIDevice *dev, uint16_t offset, uint16_t nextfn);
>  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..1db86b0 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                     0x1
> +#define PCI_ACS_SIZEOF                  8
> +
>  #endif /* QEMU_PCIE_REGS_H */