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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Qemu-devel] [PATCH 2/2] xen:i386:pc_piix: create isa bridge specific to IGD passthrough
On Sun, Sep 28, 2014 at 10:59:05AM +0800, Chen, Tiejun wrote:
> On 2014/9/3 9:40, Kay, Allen M wrote:
> >
> >
> >>-----Original Message-----
> >>From: Chen, Tiejun
> >>Sent: Monday, September 01, 2014 12:50 AM
> >>To: Michael S. Tsirkin
> >>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Kay, Allen M; qemu-devel@xxxxxxxxxx;
> >>Konrad Rzeszutek Wilk
> >>Subject: Re: [Qemu-devel] [Xen-devel] [PATCH 2/2] xen:i386:pc_piix: create
> >>isa bridge specific to IGD passthrough
> >>
> >>On 2014/9/1 14:05, Michael S. Tsirkin wrote:
> >>>On Mon, Sep 01, 2014 at 10:50:37AM +0800, Chen, Tiejun wrote:
> >>>>On 2014/8/31 16:58, Michael S. Tsirkin wrote:
> >>>>>On Fri, Aug 29, 2014 at 09:28:50AM +0800, Chen, Tiejun wrote:
> >>>>>>
> >>>>>>
> >>>>>>On 2014/8/28 8:56, Chen, Tiejun wrote:
> >>>>>>>>>>>>>+ */
> >>>>>>>>>>>>>+ dev = pci_create_simple(bus, PCI_DEVFN(0x1f, 0),
> >>>>>>>>>>>>>+ "xen-igd-passthrough-isa-bridge");
> >>>>>>>>>>>>>+ if (dev) {
> >>>>>>>>>>>>>+ r = xen_host_pci_device_get(&hdev, 0, 0,
> >>>>>>>>>>>>>+ PCI_DEVFN(0x1f,
> >>>>>>>>>>>>>0), 0);
> >>>>>>>>>>>>>+ if (!r) {
> >>>>>>>>>>>>>+ pci_config_set_vendor_id(dev->config,
> >>hdev.vendor_id);
> >>>>>>>>>>>>>+ pci_config_set_device_id(dev->config,
> >>>>>>>>>>>>>+ hdev.device_id);
> >>>>>>>>>>
> >>>>>>>>>>Can you, instead, implement the reverse logic, probing the card
> >>>>>>>>>>and supplying the correct device id for PCH?
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>Here what is your so-called reverse logic as I already asked you
> >>>>>>>>>previously? Do you mean I should list all PCHs with a combo
> >>>>>>>>>illustrated with the vendor/device id in advance? Then look up
> >>>>>>>>>if we can find a
> >>>>>>>>
> >>>>>>>>Michael,
> >>>>>>>>
> >>>>>>>
> >>>>>>>Ping.
> >>>>>>>
> >>>>>>>Thanks
> >>>>>>>Tiejun
> >>>>>>>
> >>>>>>>>Could you explain this exactly? Then I can try follow-up your
> >>>>>>>>idea ASAP if this is necessary and possible.
> >>>>>>
> >>>>>>Michel,
> >>>>>>
> >>>>>>Could you give us some explanation for your "reverse logic" when
> >>>>>>you're free?
> >>>>>>
> >>>>>>Thanks
> >>>>>>Tiejun
> >>>>>
> >>>>>So future drivers will look at device ID for the card and figure out
> >>>>>how things should work from there.
> >>>>>Old drivers still poke at device id of the chipset for this, but
> >>>>>maybe qemu can do what newer drivers do:
> >>>>>look at the card and figure out what guest should do, then present
> >>>>>the appropriate chipset id.
> >>>>>
> >>>>>This is based on what Jesse said:
> >>>>> Practically speaking, we could probably assume specific GPU/PCH
> >>combos,
> >>>>> as I don't think they're generally mixed across generations, though
> >>SNB
> >>>>> and IVB did have compatible sockets, so there is the possibility of
> >>>>> mixing CPT and PPT PCHs, but those are register identical as far as the
> >>>>> graphics driver is concerned, so even that should be safe.
> >>>>>
> >>>>
> >>>>Michael,
> >>>>
> >>>>Thanks for your explanation.
> >>>>
> >>>>>so the idea is to have a reverse table mapping GPU back to PCH.
> >>>>>Present to guest the ID that will let it assume the correct GPU.
> >>>>
> >>>>I guess you mean we should create to maintain such a table:
> >>>>
> >>>>[GPU Card: device_id(s), PCH: device_id]
> >>>>
> >>>>Then each time, instead of exposing that real PCH device id directly,
> >>>>qemu first can get the real GPU device id to lookup this table to
> >>>>present a appropriate PCH's device id to the guest.
> >>>>
> >>>>And looks here that appropriate PCH's device id is not always a that
> >>>>real PCH's device id. Right? If I'm wrong please correct me.
> >>>
> >>>Exactly: we don't really care what the PCH ID is - we only need it for
> >>>the guest driver to do the right thing.
> >>
> >>Agreed.
> >>
> >>I need to ask Allen to check if one given GPU card device id is always
> >>corresponding to one given PCH on both HSW and BDW currently. If yes, I can
> >>do this quickly. Otherwise I need some time to establish that sort
> >>of connection.
>
> Michael,
>
> Sorry for this delay response but please keep in mind we really are in this
> process.
>
> You know this involve different GPU components we have to take some time to
> communicate or even discuss internal.
>
> Now I have a draft codes, could you take a look at this? I hope that comment
> can help us to understand something, but if you have any question, we can
> further respond inline.
>
> ---
> typedef struct {
> uint16_t gpu_device_id;
> uint16_t pch_device_id;
> } XenIGDDeviceIDInfo;
>
> /* In real world different GPU should have different PCH. But actually
> * the different PCH DIDs likely map to different PCH SKUs. We do the
> * same thing for the GPU. For PCH, the different SKUs are going to be
> * all the same silicon design and implementation, just different
> * features turn on and off with fuses. The SW interfaces should be
> * consistent across all SKUs in a given family (eg LPT). But just same
> * features may not be supported.
> *
> * Most of these different PCH features probably don't matter to the
> * Gfx driver, but obviously any difference in display port connections
> * will so it should be fine with any PCH in case of passthrough.
> *
> * So currently use one PCH version, 0x8c4e, to cover all HSW scenarios,
> * 0x9cc3 for BDW.
Pls write Haswell and Broadwell in full in comment.
> */
> static const XenIGDDeviceIDInfo xen_igd_combo_id_infos[] = {
> /* HSW Classic */
> {0x0402, 0x8c4e}, /* HSWGT1D, HSWD_w7 */
> {0x0406, 0x8c4e}, /* HSWGT1M, HSWM_w7 */
> {0x0412, 0x8c4e}, /* HSWGT2D, HSWD_w7 */
> {0x0416, 0x8c4e}, /* HSWGT2M, HSWM_w7 */
> {0x041E, 0x8c4e}, /* HSWGT15D, HSWD_w7 */
> /* HSW ULT */
> {0x0A06, 0x8c4e}, /* HSWGT1UT, HSWM_w7 */
> {0x0A16, 0x8c4e}, /* HSWGT2UT, HSWM_w7 */
> {0x0A26, 0x8c4e}, /* HSWGT3UT, HSWM_w7 */
> {0x0A2E, 0x8c4e}, /* HSWGT3UT28W, HSWM_w7 */
> {0x0A1E, 0x8c4e}, /* HSWGT2UX, HSWM_w7 */
> {0x0A0E, 0x8c4e}, /* HSWGT1ULX, HSWM_w7 */
> /* HSW CRW */
> {0x0D26, 0x8c4e}, /* HSWGT3CW, HSWM_w7 */
> {0x0D22, 0x8c4e}, /* HSWGT3CWDT, HSWD_w7 */
> /* HSW Server */
> {0x041A, 0x8c4e}, /* HSWSVGT2, HSWD_w7 */
> /* HSW SRVR */
> {0x040A, 0x8c4e}, /* HSWSVGT1, HSWD_w7 */
> /* BSW */
> {0x1606, 0x9cc3}, /* BDWULTGT1, BDWM_w7 */
> {0x1616, 0x9cc3}, /* BDWULTGT2, BDWM_w7 */
> {0x1626, 0x9cc3}, /* BDWULTGT3, BDWM_w7 */
> {0x160E, 0x9cc3}, /* BDWULXGT1, BDWM_w7 */
> {0x161E, 0x9cc3}, /* BDWULXGT2, BDWM_w7 */
> {0x1602, 0x9cc3}, /* BDWHALOGT1, BDWM_w7 */
> {0x1612, 0x9cc3}, /* BDWHALOGT2, BDWM_w7 */
> {0x1622, 0x9cc3}, /* BDWHALOGT3, BDWM_w7 */
> {0x162B, 0x9cc3}, /* BDWHALO28W, BDWM_w7 */
> {0x162A, 0x9cc3}, /* BDWGT3WRKS, BDWM_w7 */
> {0x162D, 0x9cc3}, /* BDWGT3SRVR, BDWM_w7 */
> };
>
> static void xen_igd_passthrough_pciisabridge_get_pci_device_id(Object *obj,
> Visitor *v,
> void *opaque,
> const char
> *name,
> Error **errp)
> {
> uint32_t value = 0;
> XenHostPCIDevice hdev;
> int r = 0, num;
>
> r = xen_host_pci_device_get(&hdev, 0, 0, 0x02, 0);
> if (!r) {
> value = hdev.device_id;
>
> num = sizeof(xen_igd_combo_id_infos)/sizeof(uint16_t);
> for (r = 0; r < num; r++)
> if (value == xen_igd_combo_id_infos[r].gpu_device_id)
> value = xen_igd_combo_id_infos[r].pch_device_id;
that's messy, I would use different variables for ID
of GPU and PCH.
> }
>
> visit_type_uint32(v, &value, name, errp);
what I was suggesting is to start with the GPU device ID
(you can get it e.g. from the config array).
Use that to look up the PCH ID in xen_igd_combo_id_infos.
If there, override the PCH ID.
If not there, this is a new device so its driver will
not look at PCH at all, we can make it whatever or
skip it completely.
This seems to almost do this, however
- Why are you looking at host PCH device ID at all?
- Why don't you look at the GPU device ID?
> }
>
> static void xen_igd_passthrough_isa_bridge_initfn(Object *obj)
> {
> object_property_add(obj, "device-id", "int",
> xen_igd_passthrough_pciisabridge_get_pci_device_id,
> NULL, NULL, NULL, NULL);
> }
OK and what reads this property?
> Thanks
> Tiejun
>
>
> >>
> >
> >If I understand this correctly, the only difference is instead of reading
> >PCH DevID/RevID from the host hardware, QEMU inserts those values into PCH
> >virtual device by looking at the reverse mapping table it maintains.
> >
> >I agree the downside of doing this is the reverse mapping table may be hard
> >to maintain.
> >
> >What is the advantage of doing this instead of having QEMU reading it from
> >the host? Is it to test to make sure reverse mapping methods works before
> >it is adopted in the new drivers?
> >
> >>Thanks
> >>Tiejun
> >>
> >>>
> >>>>>
> >>>>>the problem with these tables is they are hard to keep up to date
> >>>>
> >>>>Yeah. But I think currently we can just start from some modern CPU
> >>>>such as HSW and BDW, then things could be easy.
> >>>>
> >>>>Allen,
> >>>>
> >>>>Any idea to this suggestion?
> >>>>
> >>>>>as new hardware comes out, but as future hardware won't need these
> >>>>>hacks, we shall be fine.
> >>>>
> >>>>Yeah.
> >>>>
> >>>>Thanks
> >>>>Tiejun
> >>>>
> >>>>>
> >>>>>
> >>>>>>>>
> >>>>>>>>Thanks
> >>>>>>>>Tiejun
> >>>>>>>>
> >>>>>>>>>matched PCH? If yes, what is that benefit you expect in
> >>>>>>>>>passthrough case? Shouldn't we pass these info to VM directly in
> >>passthrough case?
> >>>>>>>>>
> >>>>>>>>>Thanks
> >>>>>>>>>Tiejun
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>
> >>>
> >>>
> >
> >Allen
> >
> >
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