Date: Mon, 04 Jan 2021 18:36:44 -0800 From: Neel Chauhan <nc@freebsd.org> To: Doug Ambrisko <ambrisko@ambrisko.com> Cc: Mark Johnston <markj@freebsd.org>, freebsd-hackers@freebsd.org, ambrisko@freebsd.org Subject: Re: Debugging a WIP PCI/ACPI patch: Bad tailq NEXT(0xffffffff81cde660->tqh_last) != NULL Message-ID: <1aa63edbf7abb4f6b3f0d8c18bd948e0@freebsd.org> In-Reply-To: <20210102190644.GB87535@ambrisko.com> References: <44528336fa9168966d121bf771e1e229@neelc.org> <X%2ByzpNIclmFYgbr7@raichu> <3c9ff844e527daacd04c51f48836b57d@neelc.org> <dbcc0e54eeb0080620ee4fb6d14845fc@neelc.org> <e73228a75b8f05c83214c62ed7e1ba68@neelc.org> <X%2B3tfbxHGdiW1Kvt@raichu> <20201231200744.GA95383@ambrisko.com> <4f3f6a02a452f766063ae2acb060dc64@neelc.org> <7cda3be6594d5ad5bdc69019f72b03d3@neelc.org> <20210102190644.GB87535@ambrisko.com>
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Unrelated to VMD, but I have recently gotten a Ports commit bit and now
have a @FreeBSD.org email, in case you wanted to know who to give credit
to. It's still me, and it forwards to ${FIRSTNAME}@neelc.org.
My handle is nc@.
-Neel
On 2021-01-02 11:06, Doug Ambrisko wrote:
> With VMD, the PCI "root" is hidden behind it. To access devices behind
> the VMD device, a new domain is created and when PCI config. space
> is accessed, it is indexed via the VMD device via the offset. Intel
> seems to have reduced the available bus space on some HW. So for a bus
> access less then what they implemented in HW we have to return error
> that nothing is there. Then when we get to the starting bus device,
> we need to offset that to 0 based in the HW. The PCI probe will run
> look for busses from 0 to 255. From the Linux driver your HW only
> works
> from 224 to 255. So we need to fail anything under 224 and for bus
> requests 224 and higher then subtract 224. Thus the b -
> sc->vmd_bus_start
> part. I'm not sure if we could do it the other way in which we allow
> 0-12 bus requests to pass and fail if it is over. I'm not sure if
> there is any specific reason why that wouldn't work. Linux didn't
> do that but that doesn't mean it wouldn't work. It would be good to
> start with the Linux method and then test 0-n, where n is the max.
> busses that HW allows. Anything n or more would have to return a fail.
>
> Doug A.
>
> On Sat, Jan 02, 2021 at 09:20:20AM -0800, Neel Chauhan wrote:
> | Just to ping you in case you may have missed my reply (I understand,
> New
> | Years Day).
> |
> | Is there a reason why "b = pci_get_bus(dev);" return 0 even when the
> bus
> | number is shifted (as it is on Linux)?
> |
> | -Neel
> |
> | On 2020-12-31 21:49, Neel Chauhan wrote:
> | > Hi Doug,
> | >
> | > Thank you so much for this information.
> | >
> | > On 2020-12-31 12:07, Doug Ambrisko wrote:
> | >> FYI, looks like this needs to be ported over from Linux:
> | >> static char __iomem *vmd_cfg_addr(struct vmd_dev *vmd, struct
> pci_bus
> | >> *bus,
> | >> unsigned int devfn, int reg, int
> | >> len)
> | >> {
> | >> char __iomem *addr = vmd->cfgbar +
> | >> ((bus->number - vmd->busn_start) <<
> 20) +
> | >> (devfn << 12) + reg;
> | >>
> | >> to
> | >> vmd_read_config
> | >> offset = (b << 20) + (s << 15) + (f << 12) + reg;
> | >>
> | >> vmd_write_config(device_t dev, u_int b, u_int s, u_int f, u_int
> reg,
> | >> offset = (b << 20) + (s << 15) + (f << 12) + reg;
> | >>
> | >> ie.
> | >> offset = ((b - sc->vmd_bus_start) << 20) + (s << 15) + (f << 12)
> +
> | >> reg;
> | >>
> | >> vmd_bus_start should be added to the softc as a uint8_t type and
> needs
> | >> to
> | >> be set via attach. We need range checks to make sure
> | >> vmd_write_config/vmd_read_config doesn't read something out of
> range
> | >> since it has been reduced.
> | >
> | > One thing I noticed is that the "b" variable (which corresponds to
> the
> | > Linux bus->number) is 0 (thanks to printf). This should be the bus
> | > number if we want to attach.
> | >
> | > If I use: "b = pci_get_bus(dev);" in the attach, b is still 0.
> | >
> | > And that leads to a kernel panic.
> | >
> | >> Not sure what the shadow registers do. These both seem to be new
> | >> Intel
> | >> features and Intel doc's have been minimal. Looks like Intel is
> doing
> | >> a sparse map now on newer devices.
> | >
> | > I guess Linux is our best hope. Unless the new Intel docs is the
> Linux
> | > kernel source.
> | >
> | >> I'm concerned about the Linux comment of:
> | >> * Certain VMD devices may have a root port configuration
> | >> option which
> | >> * limits the bus range to between 0-127, 128-255, or
> 224-255
> | >>
> | >> since I don't see anything to limit it between 0-127 only starting
> | >> at 0, 128 or 224, Maybe there is max of 128 busses overall?
> | >
> | > I could be wrong, but I guess that's a typo.
> | >
> | >> I don't have this type of HW to test things.
> | >
> | > I can use my hardware for testing. In the worse case scenario, I
> can
> | > donate an entry-level 11th Gen/TigerLake system if I have the funds
> | > and/or can get a tax credit.
> | >
> | >> Doug A.
> | >
> | > -Neel
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