Please sign in to comment.
KVM: Don't automatically expose the TSC deadline timer in cpuid
Unlike all of the other cpuid bits, the TSC deadline timer bit is set unconditionally, regardless of what userspace wants. This is broken in several ways: - if userspace doesn't use KVM_CREATE_IRQCHIP, and doesn't emulate the TSC deadline timer feature, a guest that uses the feature will break - live migration to older host kernels that don't support the TSC deadline timer will cause the feature to be pulled from under the guest's feet; breaking it - guests that are broken wrt the feature will fail. Fix by not enabling the feature automatically; instead report it to userspace. Because the feature depends on KVM_CREATE_IRQCHIP, which we cannot guarantee will be called, we expose it via a KVM_CAP_TSC_DEADLINE_TIMER and not KVM_GET_SUPPORTED_CPUID. Fixes the Illumos guest kernel, which uses the TSC deadline timer feature. [avi: add the KVM_CAP + documentation] Reported-by: Alexey Zaytsev <email@example.com> Tested-by: Alexey Zaytsev <firstname.lastname@example.org> Signed-off-by: Jan Kiszka <email@example.com> Signed-off-by: Avi Kivity <firstname.lastname@example.org>
- Loading branch information...
Showing with 19 additions and 10 deletions.