Marcelo, On Thu, Aug 26, 2021 at 09:48:36AM -0300, Marcelo Tosatti wrote: > 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? Apologies for not getting back to you on your first mail. Sadly, I am using our own userspace for this. That being said, adding support to QEMU shouldn't be too challenging. I can take a stab at it if it makes the series more amenable to upstream, with the giant disclaimer that I haven't done work in QEMU before. Otherwise, happy to review someone else's implementation. -- Thanks, Oliver _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
