On 10/31/2024 12:05 PM, Easwar Hariharan wrote: > On 10/3/2024 12:50 PM, Nuno Das Neves wrote: >> To support Hyper-V Dom0 (aka Linux as root partition), many new >> definitions are required. >> >> The plan going forward is to directly import headers from >> Hyper-V. This is a more maintainable way to import definitions >> rather than via the TLFS doc. This patch series introduces >> new headers (hvhdk.h, hvgdk.h, etc, see patch #3) directly >> derived from Hyper-V code. >> >> This patch series replaces hyperv-tlfs.h with hvhdk.h, but only >> in Microsoft-maintained Hyper-V code where they are needed. This >> leaves the existing hyperv-tlfs.h in use elsewhere - notably for >> Hyper-V enlightenments on KVM guests. >> >> An intermediary header "hv_defs.h" is introduced to conditionally >> include either hyperv-tlfs.h or hvhdk.h. This is required because >> several headers which today include hyperv-tlfs.h, are shared >> between Hyper-V and KVM code (e.g. mshyperv.h). >> >> Summary: >> Patch 1-2: Cleanup patches >> Patch 3: Add the new headers (hvhdk.h, etc..) in include/hyperv/ >> Patch 4: Add hv_defs.h and use it in mshyperv.h, svm.h, >> hyperv_timer.h >> Patch 5: Switch to the new headers, only in Hyper-V code >> >> Nuno Das Neves (5): >> hyperv: Move hv_connection_id to hyperv-tlfs.h >> hyperv: Remove unnecessary #includes >> hyperv: Add new Hyper-V headers >> hyperv: Add hv_defs.h to conditionally include hyperv-tlfs.h or >> hvhdk.h >> hyperv: Use hvhdk.h instead of hyperv-tlfs.h in Hyper-V code >> Hi Easwar, thanks for the questions. I will attempt to clarify. > > What is the model for Hyper-V code that has both guest and host roles > where the corresponding hypercalls are available for both? As I > understand it, those are supposed to be in hvgdk*.h. > It's true that the naming of the files implies hvgdk*.h is for guests, and hvhdk*.h (which includes hvgdk*.h), is for hosts/dom0. But I would only take that as a rough guide. The real reason for keeping these names is to make it a easier to copy and maintain the definitions from the Windows code into Linux, by keeping the provenance of exactly where they came from. > For a specific example, IOMMU hypercalls can operate on stage 2 or stage > 1 translations depending on the role of the (hyper) caller and the input > values provided. Should a driver using these hypercalls import both > hvhdk* and hvgdk*? What about hyperv-tlfs? > I'd recommend importing hvhdk.h since it contains everything you need (including hvgdk*.h). The goal of this patchset is to move away from hyperv-tlfs.h, because by definition it should only contain definitions from the TLFS document. > Patches 4 and 5 seem to draw a bright line between host and guest roles > while the reality is more gray. Please do correct me if I'm wrong here, > perhaps the picture would be clearer if Stas' suggestion of a new header > file is implemented. > Patches 4 and 5 introduce the new headers in a way that avoids any potential impact on KVM and other non-Microsoft-maintained code. The 'line' is not between guest and host, but between Microsoft-maintained and non-Microsoft-maintained code. Thanks, Nuno > Thanks, > Easwar
