On Wed, Nov 08, 2023, Nicolas Saenz Julienne wrote: > This RFC series introduces the necessary infrastructure to emulate VSM > enabled guests. It is a snapshot of the progress we made so far, and its > main goal is to gather design feedback. Heh, then please provide an overview of the design, and ideally context and/or justification for various design decisions. It doesn't need to be a proper design doc, and you can certainly point at other documentation for explaining VSM/VTLs, but a few paragraphs and/or verbose bullet points would go a long way. The documentation in patch 33 provides an explanation of VSM itself, and a little insight into how userspace can utilize the KVM implementation. But the documentation provides no explanation of the mechanics that KVM *developers* care about, e.g. the use of memory attributes, how memory attributes are enforced, whether or not an in-kernel local APIC is required, etc. Nor does the documentation explain *why*, e.g. why store a separate set of memory attributes per VTL "device", which by the by is broken and unnecessary. > Specifically on the KVM APIs we introduce. For a high level design overview, > see the documentation in patch 33. > > Additionally, this topic will be discussed as part of the KVM > Micro-conference, in this year's Linux Plumbers Conference [2]. > > The series is accompanied by two repositories: > - A PoC QEMU implementation of VSM [3]. > - VSM kvm-unit-tests [4]. > > Note that this isn't a full VSM implementation. For now it only supports > 2 VTLs, and only runs on uniprocessor guests. It is capable of booting > Windows Sever 2016/2019, but is unstable during runtime. > > The series is based on the v6.6 kernel release, and depends on the > introduction of KVM memory attributes, which is being worked on > independently in "KVM: guest_memfd() and per-page attributes" [5]. This doesn't actually apply on 6.6 with v14 of guest_memfd, because v14 of guest_memfd is based on kvm-6.7-1. Ah, and looking at your github repo, this isn't based on v14 at all, it's based on v12. That's totally fine, but the cover letter needs to explicitly, clearly, and *accurately* state the dependencies. I can obviously grab the full branch from github, but that's not foolproof, e.g. if you accidentally delete or force push to that branch. And I also prefer to know that what I'm replying to on list is the exact same code that I am looking at. > A full Linux tree is also made available [6]. > > Series rundown: > - Patch 2 introduces the concept of APIC ID groups. > - Patches 3-12 introduce the VSM capability and basic VTL awareness into > Hyper-V emulation. > - Patch 13 introduces vCPU polling support. > - Patches 14-31 use KVM's memory attributes to implement VTL memory > protections. Introduces the VTL KMV device and secure memory > intercepts. > - Patch 32 is a temporary implementation of > HVCALL_TRANSLATE_VIRTUAL_ADDRESS necessary to boot Windows 2019. > - Patch 33 introduces documentation. > > Our intention is to integrate feedback gathered in the RFC and LPC while > we finish the VSM implementation. In the future, we will split the series > into distinct feature patch sets and upstream these independently. > > Thanks, > Nicolas > > [1] https://raw.githubusercontent.com/Microsoft/Virtualization-Documentation/master/tlfs/Hypervisor%20Top%20Level%20Functional%20Specification%20v6.0b.pdf > [2] https://lpc.events/event/17/sessions/166/#20231114 > [3] https://github.com/vianpl/qemu/tree/vsm-rfc-v1 > [4] https://github.com/vianpl/kvm-unit-tests/tree/vsm-rfc-v1 > [5] https://lore.kernel.org/lkml/20231105163040.14904-1-pbonzini@xxxxxxxxxx/. > [6] Full tree: https://github.com/vianpl/linux/tree/vsm-rfc-v1. When providing github links, my preference is to format the pointers as: <repo> <branch> or <repo> tags/<tag> e.g. https://github.com/vianpl/linux vsm-rfc-v1 so that readers can copy+paste the full thing directly into `git fetch`. It's a minor thing, but AFAIK no one actually does review by clicking through github's webview. > There are also two small dependencies with > https://marc.info/?l=kvm&m=167887543028109&w=2 and > https://lkml.org/lkml/2023/10/17/972 Please use lore links, there's zero reason to use anything else these days. For those of us that use b4, lore links make life much easier.
