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    SubjectRe: [PATCH 0/4] Avoid soft lockup message when KVM is stopped by host
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    On Tue, Aug 30, 2011 at 06:26, Marcelo Tosatti <mtosatti@redhat.com> wrote:
    > On Mon, Aug 29, 2011 at 05:27:11PM -0600, Eric B Munson wrote:
    >> Currently, when qemu stops a guest kernel that guest will issue a soft lockup
    >> message when it resumes.  This set provides the ability for qemu to comminucate
    >> to the guest that it has been stopped.  When the guest hits the watchdog on
    >> resume it will check if it was suspended before issuing the warning.
    >>
    >> Eric B Munson (4):
    >>   Add flag to indicate that a vm was stopped by the host
    >>   Add functions to check if the host has stopped the vm
    >>   Add generic stubs for kvm stop check functions
    >>   Add check for suspended vm in softlockup detector
    >>
    >>  arch/x86/include/asm/pvclock-abi.h |    1 +
    >>  arch/x86/include/asm/pvclock.h     |    2 ++
    >>  arch/x86/kernel/kvmclock.c         |   14 ++++++++++++++
    >>  include/asm-generic/pvclock.h      |   14 ++++++++++++++
    >>  kernel/watchdog.c                  |   12 ++++++++++++
    >>  5 files changed, 43 insertions(+), 0 deletions(-)
    >>  create mode 100644 include/asm-generic/pvclock.h
    >>
    >> --
    >> 1.7.4.1
    >
    > How is the host supposed to set this flag?

    The hypervisor will set the flag (the second bit in the struct
    pvclock_vcpu_time_info.flags field) when it stops the guest. I could
    be reading pvclock-abi.h incorrectly, but the way I understand it is
    that this structure is used to communicate between hypervisor and
    guest.

    >
    > As mentioned previously, if you save save/restore the offset added to
    > kvmclock on stop/cont (and the TSC MSR, forgot to mention that), no
    > paravirt infrastructure is required. Which means the issue is also fixed
    > for older guests.
    >
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