On 16.10.19 18:04, Julien Grall wrote:
Hi,
Hi Julien
just my 2 cents)
Below is example from linux kernel sources:
linux/sound/ppc/awacs.c:741: if
(of_machine_is_compatible("PowerBook3,1")
linux/sound/ppc/awacs.c:742: ||
of_machine_is_compatible("PowerBook3,2")) {
linux/sound/ppc/awacs.c:770:#define IS_PM7500
(of_machine_is_compatible("AAPL,7500") \
linux/sound/ppc/awacs.c:771: ||
of_machine_is_compatible("AAPL,8500") \
linux/sound/ppc/awacs.c:772: ||
of_machine_is_compatible("AAPL,9500"))
...
linux/arch/arm/mach-omap2/pdata-quirks.c:703: if
(of_machine_is_compatible(quirks->compatible)) {
linux/arch/arm/mach-omap2/pdata-quirks.c:717: if
(of_machine_is_compatible("ti,omap2420") ||
linux/arch/arm/mach-omap2/pdata-quirks.c:718:
of_machine_is_compatible("ti,omap3"))
linux/arch/arm/mach-omap2/pdata-quirks.c:721: if
(of_machine_is_compatible("ti,omap3"))
...
Also see [1]
[1]
https://source.codeaurora.org/external/imx/imx-xen/commit/?h=imx_4.14.98_2.0.0_ga&id=6e58d478203639e71da3da69ffeae3fa5dc0197b
So this is a grep from Linux, I have already done that. What I am
looking at is an exact description of your problem. Can you tell me
what you are trying to passthrough? Can you also provide a pointer to
the Linux code checking the compatible for your problem?
I have no idea whether it is ok or not to pass machine/SoC compatible to
a guest from the safety PoV, so I am not going to comment regarding safety.
I just would like to provide description of the problem we could face
when not passing machine/SoC compatible to a guest which runs real H/W
(not PV) devices.
...
I have just checked without passing real "dt_compatible" to a guest on
the M3N board. So, this can be considered as real example.
I noticed that at least two H/W devices (which are pass throughed to the
guest) suffered from the lack of compatible: sdhi_internal_dmac and
xhci-hcd. And as result SD card and USB host are not functional.
Why this happened? There is SoC Identification framework which purpose
is to detect SoC's id/revision for the future use in drivers to properly
apply some quirks (if needed). And without real compatible string in
place the framework fails
to proceed leaving the SoC attributes unregistered [1]. This results in
SDHI Internal DMAC controller fails to identify the SoC [2], so can't
operate.
I didn't investigate what is wrong with the xHCI, but I tend to think
that the problem is close to what we have with the SDHI.
[1]
https://elixir.bootlin.com/linux/v5.4-rc2/source/drivers/soc/renesas/renesas-soc.c#L292
[2]
https://elixir.bootlin.com/linux/v5.4-rc2/source/drivers/mmc/host/renesas_sdhi_internal_dmac.c#L328
--
Regards,
Oleksandr Tyshchenko
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