On Mon, Aug 23, 2021 at 01:56:30PM -0700, Oliver Upton wrote: > Paolo, > > On Sun, Aug 15, 2021 at 5:11 PM Oliver Upton <oupton@xxxxxxxxxx> wrote: > > > > To date, VMM-directed TSC synchronization and migration has been a bit > > messy. KVM has some baked-in heuristics around TSC writes to infer if > > the VMM is attempting to synchronize. This is problematic, as it depends > > on host userspace writing to the guest's TSC within 1 second of the last > > write. > > > > A much cleaner approach to configuring the guest's views of the TSC is to > > simply migrate the TSC offset for every vCPU. Offsets are idempotent, > > and thus not subject to change depending on when the VMM actually > > reads/writes values from/to KVM. The VMM can then read the TSC once with > > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when > > the guest is paused. > > > > Cc: David Matlack <dmatlack@xxxxxxxxxx> > > Cc: Sean Christopherson <seanjc@xxxxxxxxxx> > > Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx> > > Could you please squash the following into this patch? We need to > advertise KVM_CAP_VCPU_ATTRIBUTES to userspace. Otherwise, happy to > resend. > > Thanks, > Oliver Oliver, Is there QEMU support for this, or are you using your own userspace with this?
