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f0b5105af6
Allowing an unlimited number of MSRs to be specified via the VMX load/store MSR lists (e.g., vm-entry MSR load list) is bad for two reasons. First, a guest can specify an unreasonable number of MSRs, forcing KVM to process all of them in software. Second, the SDM bounds the number of MSRs allowed to be packed into the atomic switch MSR lists. Quoting the "Miscellaneous Data" section in the "VMX Capability Reporting Facility" appendix: "Bits 27:25 is used to compute the recommended maximum number of MSRs that should appear in the VM-exit MSR-store list, the VM-exit MSR-load list, or the VM-entry MSR-load list. Specifically, if the value bits 27:25 of IA32_VMX_MISC is N, then 512 * (N + 1) is the recommended maximum number of MSRs to be included in each list. If the limit is exceeded, undefined processor behavior may result (including a machine check during the VMX transition)." Because KVM needs to protect itself and can't model "undefined processor behavior", arbitrarily force a VM-entry to fail due to MSR loading when the MSR load list is too large. Similarly, trigger an abort during a VM exit that encounters an MSR load list or MSR store list that is too large. The MSR list size is intentionally not pre-checked so as to maintain compatibility with hardware inasmuch as possible. Test these new checks with the kvm-unit-test "x86: nvmx: test max atomic switch MSRs". Suggested-by: Jim Mattson <jmattson@google.com> Reviewed-by: Jim Mattson <jmattson@google.com> Reviewed-by: Peter Shier <pshier@google.com> Signed-off-by: Marc Orr <marcorr@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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