Hi Alex, Thank you very much for the detailed explanation. On 4/4/2017 3:39 PM, Alex Williamson wrote: > On Tue, 4 Apr 2017 14:47:58 -0400 > Sinan Kaya <okaya@xxxxxxxxxxxxxx> wrote: > [cut] >> The requirement is to have an >> 1. ACS capability with PCI_ACS_SV if p2p is not supported >> 2. ACS capability with PCI_ACS_SV|PCI_ACS_RR | PCI_ACS_CR | >> PCI_ACS_UF if p2p is supported. >> >> Did I get this right? > I'm looking for sanity check on OS requirements. According to the PCIE spec, ACS itself is optional. However, Linux requires ACS capability. I want to make sure that we are satisfying the Linux requirements here. I also agree that spec should be the guide. Maybe, a combination of spec+linux is the right answer. > I'd suggest following the spec, not the code, that way you always have a > case for how you interpret the spec and the behavior of your hardware. > The code is an attempt to validate the device against the spec, but more > thorough implementations may follow. REQ_ACS_FLAGS defines the set of > ACS capabilities we think are relevant to device isolation. In > particular, UF seems like a key feature and our current test for it may > not be fully correct. Note how RR and CR only specify p2p with other > root ports while UF requires transaction towards to the RC. Section > 6.12.2 further defines Redirected Request Validation as a feature > within the context of RR and CR. So rather than look at the code, > discuss section 6.12 with the hardware engineers and understand how it > behaves relative to each device and transaction type. Implement the > capabilities that best match. Attempting a minimal implementation > based on the current software interpretation may bite later, for > instance if we re-interpret how UF works. Thanks, I read your reply multiple times. Here is what I got from it. The summary below is for the root ports only. - P2P on root ports is optional. - If P2P is there source validation, translation blocking, upstream forwarding, p2p request redirection and p2p completion redirection ACS capabilities need to be there for spec+linux compliance. - If P2P is not there source validation, translation blocking and upstream forwarding needs to be there for spec+linux compliance. - The code is relaxed to allow any combination of these today based on the ACS capability but it can change tomorrow. Sinan -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
