Messages in this thread | | | Date | Thu, 28 Mar 2024 09:30:11 +0800 | Subject | Re: [PATCH v19 059/130] KVM: x86/tdp_mmu: Don't zap private pages for unsupported cases | From | Xiaoyao Li <> |
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On 3/28/2024 9:06 AM, Edgecombe, Rick P wrote: > On Thu, 2024-03-28 at 08:58 +0800, Xiaoyao Li wrote: >>> How so? Userspace needs to learn to create a TD first. >> >> The current ABI of KVM_EXIT_X86_RDMSR/WRMSR is that userspace itself >> sets up MSR fitler at first, then it will get such EXIT_REASON when >> guest accesses the MSRs being filtered. >> >> If you want to use this EXIT reason, then you need to enforce userspace >> setting up the MSR filter. How to enforce? > > I think Isaku's proposal was to let userspace configure it. > > For the sake of conversation, what if we don't enforce it? The downside of not enforcing it is that > we then need to worry about code paths in KVM the MTRRs would call. But what goes wrong > functionally? If userspace doesn't fully setup a TD things can go wrong for the TD. > > A plus side of using the MSR filter stuff is it reuses existing functionality. > >> If not enforce, but exit with >> KVM_EXIT_X86_RDMSR/WRMSR no matter usersapce sets up MSR filter or not. >> Then you are trying to introduce divergent behavior in KVM. > > The current ABI of KVM_EXIT_X86_RDMSR when TDs are created is nothing. So I don't see how this is > any kind of ABI break. If you agree we shouldn't try to support MTRRs, do you have a different exit > reason or behavior in mind?
Just return error on TDVMCALL of RDMSR/WRMSR on TD's access of MTRR MSRs.
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