On Mon, Jan 31, 2022 at 11:57 AM Rajat Jain <rajatja@xxxxxxxxxx> wrote: > > Hello Mika, Rafael, > > On Sun, Jan 30, 2022 at 10:42 PM Mika Westerberg > <mika.westerberg@xxxxxxxxxxxxxxx> wrote: > > > > Hi, > > > > On Sun, Jan 30, 2022 at 03:30:39PM +0100, Rafael J. Wysocki wrote: > > > > I'm open to doing so if the others also feel the same way. IMHO > > > > though, the semantics of ACPI "DmaProperty" differ from the semantics > > > > of the property I'm proposing here. > > > > > > > > The current (documented) semantics (of "DmaProperty"): *This device > > > > (root port) is trusted*, but any devices downstream are not to be > > > > trusted. > > > > > > > > What I need and am proposing (new "UntrustedDevice"): *This device as > > > > well as any downstream devices* are untrusted. > > > > > > > > Note that there may be firmware implementing "DmaProperty" already out > > > > there (for windows), and if we decide to use it for my purposes, then > > > > there shall be a discrepancy in how Linux uses that property vs > > > > Windows. Is that acceptable? > > > > > > It may be confusing, so I'd rather not do that. > > > > > > The platform firmware will use it with the Windows use case in mind > > > and if it has side effects in Linux, problems are likely to appear in > > > the field. > > > > > > So the question is rather not about it being acceptable, but about > > > whether or not this is generally going to work. > > > > I was kind of implying that we could perhaps contact Microsoft and ask > > them if the wording could be changed to cover all the devices, not just > > PCIe root ports. I think this is something they will also need for > > things like internal WI-FI controllers. > > We (Chromeos) do not have a contact at Microsoft, not sure if Intel > does. If someone can point me to a contact I will be happy to initiate > a conversation. However, given that they have already published it, > and changing the semantics might mean they will also have to change > windows implementation. Not sure if we have enough leverage with > Microsoft here, so I wouldn't have any high hopes though. To keep everyone updated, Mika has helped me initiate a conversation with Microsoft on this (Thanks a lot Mika!). We're still waiting to hear their feedback. Until then, I've posted a v2 for review at: https://patchwork.kernel.org/project/linux-pci/patch/20220202020103.2149130-1-rajatja@xxxxxxxxxx/ If we can reach an agreement with Microsoft, I can change the property name in the patch (to "DmaProperty"), but would appreciate review of any other aspects of v2 in the meantime. Thanks & Best Regards, Rajat > Like Rafael > said, we're on the receiving end here. > > Rafael, one last question: is "untrusted-device" an acceptable ACPI > property name, or does it have to be Camel case? > > Thanks & Best Regards, > > Rajat > > > > > If that's not possible then no objections adding "UntrustedDevice". We > > just need to deal with the "DmaProperty" anyway and both end up setting > > pdev->untrusted in the similar manner.
