Re: [PATCH v7 3/6] KVM: x86: Report host tsc and realtime values in KVM_GET_CLOCK
From: Paolo Bonzini <pbonzini@redhat.com>
Date: 2021-09-24 08:33:07
Also in:
kvm, kvmarm
On 20/08/21 14:46, Marcelo Tosatti wrote:
On Mon, Aug 16, 2021 at 12:11:27AM +0000, Oliver Upton wrote:quoted
Handling the migration of TSCs correctly is difficult, in part because Linux does not provide userspace with the ability to retrieve a (TSC, realtime) clock pair for a single instant in time. In lieu of a more convenient facility, KVM can report similar information in the kvm_clock structure. Provide userspace with a host TSC & realtime pair iff the realtime clock is based on the TSC. If userspace provides KVM_SET_CLOCK with a valid realtime value, advance the KVM clock by the amount of elapsed time. Do not step the KVM clock backwards, though, as it is a monotonic oscillator. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Oliver Upton <redacted>This is a good idea. Userspace could check if host and destination clocks are up to a certain difference and not use the feature if not appropriate. Is there a qemu patch for it?
Not yet, but Maxim had a patch for a similar series (though with a different userspace API). Paolo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel