Messages in this thread | | | Date | Fri, 19 Aug 2022 19:37:33 +0200 | Subject | Re: [PATCH v2 2/3] KVM: x86/mmu: Fully re-evaluate MMIO caching when SPTE masks change | From | Paolo Bonzini <> |
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On 8/19/22 18:21, David Matlack wrote: > On Wed, Aug 3, 2022 at 3:50 PM Sean Christopherson <seanjc@google.com> wrote: >> >> Fully re-evaluate whether or not MMIO caching can be enabled when SPTE >> masks change; simply clearing enable_mmio_caching when a configuration >> isn't compatible with caching fails to handle the scenario where the >> masks are updated, e.g. by VMX for EPT or by SVM to account for the C-bit >> location, and toggle compatibility from false=>true. >> >> Snapshot the original module param so that re-evaluating MMIO caching >> preserves userspace's desire to allow caching. Use a snapshot approach >> so that enable_mmio_caching still reflects KVM's actual behavior. > > Is updating module parameters to reflect the actual behavior (vs. > userspace desire) something we should do for all module parameters? > > I am doing an unrelated refactor to the tdp_mmu module parameter and > noticed it is not updated e.g. if userspace loads kvm_intel with > ept=N.
If it is cheap/easy then yeah, updating the parameters is the right thing to do. Generally, however, this is only done for kvm_intel/kvm_amd modules that depend on hardware features, because they are more important for debugging user issues. (Or at least they were until vmx features were added to /proc/cpuinfo).
Paolo
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