Re: [PATCH v5 2/2] pcie: Specify 0 for ARI next function numbers

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jul 10, 2023 at 02:49:55PM +0530, Ani Sinha wrote:
> 
> 
> > On 10-Jul-2023, at 2:46 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > 
> > On Mon, Jul 10, 2023 at 01:21:50PM +0530, Ani Sinha wrote:
> >> 
> >> 
> >>> On 05-Jul-2023, at 7:54 AM, Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
> >>> 
> >>> The current implementers of ARI are all SR-IOV devices. The ARI next
> >>> function number field is undefined for VF according to PCI Express Base
> >>> Specification Revision 5.0 Version 1.0 section 9.3.7.7. The PF should
> >>> end the linked list formed with the field by specifying 0 according to
> >>> section 7.8.7.2.
> >> 
> >> Section 7.8.7.2 ARI Capability Register (Offset 04h), I see only this
> >> 
> >> Next Function Number - This field indicates the Function Number of the next higher numbered Function in the Device, or 00h if there are no higher numbered Functions. Function 0 starts this linked list of Functions.
> >> 
> >> I do not see anything specifically for PF. What am I missing?
> > 
> > This is *only* for PFs.
> 
> I think this covers both SRIOV and non SRIOV cases both. This is a
> general case for all devices, PF or other non-SRIOV capable devices.

"this" being what? I'm talking about the pci spec text
you quoted.

check out the sriov spec:
Next Function Number – VFs are located using First
VF Offset (see Section 3.3.9) and VF Stride (see
Section 3.3.10).



> > There's separate text explaining that
> > VFs use NumVFs VFOffset and VFStride.
> > 
> > 
> >>> 
> >>> For migration, the field will keep having 1 as its value on the old
> >>> virt models.
> >>> 
> >>> Fixes: 2503461691 ("pcie: Add some SR/IOV API documentation in docs/pcie_sriov.txt")
> >>> Fixes: 44c2c09488 ("hw/nvme: Add support for SR-IOV")
> >>> Fixes: 3a977deebe ("Intrdocue igb device emulation")
> >>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> >>> ---
> >>> include/hw/pci/pci.h | 2 ++
> >>> hw/core/machine.c    | 1 +
> >>> hw/pci/pci.c         | 2 ++
> >>> hw/pci/pcie.c        | 2 +-
> >>> 4 files changed, 6 insertions(+), 1 deletion(-)
> >>> 
> >>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> >>> index e6d0574a29..9c5b5eb206 100644
> >>> --- a/include/hw/pci/pci.h
> >>> +++ b/include/hw/pci/pci.h
> >>> @@ -209,6 +209,8 @@ enum {
> >>>    QEMU_PCIE_CAP_CXL = (1 << QEMU_PCIE_CXL_BITNR),
> >>> #define QEMU_PCIE_ERR_UNC_MASK_BITNR 11
> >>>    QEMU_PCIE_ERR_UNC_MASK = (1 << QEMU_PCIE_ERR_UNC_MASK_BITNR),
> >>> +#define QEMU_PCIE_ARI_NEXTFN_1_BITNR 12
> >>> +    QEMU_PCIE_ARI_NEXTFN_1 = (1 << QEMU_PCIE_ARI_NEXTFN_1_BITNR),
> >>> };
> >>> 
> >>> typedef struct PCIINTxRoute {
> >>> diff --git a/hw/core/machine.c b/hw/core/machine.c
> >>> index 46f8f9a2b0..f0d35c6401 100644
> >>> --- a/hw/core/machine.c
> >>> +++ b/hw/core/machine.c
> >>> @@ -41,6 +41,7 @@
> >>> 
> >>> GlobalProperty hw_compat_8_0[] = {
> >>>    { "migration", "multifd-flush-after-each-section", "on"},
> >>> +    { TYPE_PCI_DEVICE, "x-pcie-ari-nextfn-1", "on" },
> >>> };
> >>> const size_t hw_compat_8_0_len = G_N_ELEMENTS(hw_compat_8_0);
> >>> 
> >>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> >>> index e2eb4c3b4a..45a9bc0da8 100644
> >>> --- a/hw/pci/pci.c
> >>> +++ b/hw/pci/pci.c
> >>> @@ -82,6 +82,8 @@ static Property pci_props[] = {
> >>>    DEFINE_PROP_UINT32("acpi-index",  PCIDevice, acpi_index, 0),
> >>>    DEFINE_PROP_BIT("x-pcie-err-unc-mask", PCIDevice, cap_present,
> >>>                    QEMU_PCIE_ERR_UNC_MASK_BITNR, true),
> >>> +    DEFINE_PROP_BIT("x-pcie-ari-nextfn-1", PCIDevice, cap_present,
> >>> +                    QEMU_PCIE_ARI_NEXTFN_1_BITNR, false),
> >>>    DEFINE_PROP_END_OF_LIST()
> >>> };
> >>> 
> >>> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> >>> index 9a3f6430e8..cf09e03a10 100644
> >>> --- a/hw/pci/pcie.c
> >>> +++ b/hw/pci/pcie.c
> >>> @@ -1030,7 +1030,7 @@ void pcie_sync_bridge_lnk(PCIDevice *bridge_dev)
> >>> /* ARI */
> >>> void pcie_ari_init(PCIDevice *dev, uint16_t offset)
> >>> {
> >>> -    uint16_t nextfn = 1;
> >>> +    uint16_t nextfn = dev->cap_present & QEMU_PCIE_ARI_NEXTFN_1 ? 1 : 0;
> >>> 
> >>>    pcie_add_capability(dev, PCI_EXT_CAP_ID_ARI, PCI_ARI_VER,
> >>>                        offset, PCI_ARI_SIZEOF);
> >>> -- 
> >>> 2.41.0
> >>> 
> >