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 03:44:04PM +0530, Ani Sinha wrote:
> 
> 
> > On 10-Jul-2023, at 3:14 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > 
> > 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?
> 
> “this” is the following line I quoted above:
> 
> "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 think it applies for all devices in general (except VFs).

For all functions of devices with ARI support, yes. Does not apply to VFs.

> > 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
> >>>>> 
> >>> 
> >