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    SubjectRe: [PATCH 3/4 V11] Add ioctl for KVMCLOCK_GUEST_STOPPED
    On 2012-02-07 19:59, Marcelo Tosatti wrote:
    > On Tue, Jan 31, 2012 at 10:35:31AM -0500, Eric B Munson wrote:
    >> Now that we have a flag that will tell the guest it was suspended, create an
    >> interface for that communication using a KVM ioctl.
    >>
    >> Signed-off-by: Eric B Munson <emunson@mgebm.net>
    >>
    >> Cc: mingo@redhat.com
    >> Cc: hpa@zytor.com
    >> Cc: ryanh@linux.vnet.ibm.com
    >> Cc: aliguori@us.ibm.com
    >> Cc: mtosatti@redhat.com
    >> Cc: kvm@vger.kernel.org
    >> Cc: linux-arch@vger.kernel.org
    >> Cc: x86@kernel.org
    >> Cc: linux-kernel@vger.kernel.org
    >> ---
    >> Changes from V10:
    >> Return the ioctl to per vcpu instead of per vm
    >> Changes from V9:
    >> Use kvm_for_each_vcpu to iterate online vcpu's
    >> Changes from V8:
    >> Make KVM_GUEST_PAUSED a per vm ioctl instead of per vcpu
    >> Changes from V7:
    >> Define KVM_CAP_GUEST_PAUSED and support check
    >> Call mark_page_dirty () after setting PVCLOCK_GUEST_STOPPED
    >> Changes from V4:
    >> Rename KVM_GUEST_PAUSED to KVMCLOCK_GUEST_PAUSED
    >> Add new ioctl description to api.txt
    >>
    >> Documentation/virtual/kvm/api.txt | 13 +++++++++++++
    >> arch/x86/kvm/x86.c | 21 +++++++++++++++++++++
    >> include/linux/kvm.h | 3 +++
    >> 3 files changed, 37 insertions(+), 0 deletions(-)
    >>
    >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
    >> index e1d94bf..1931e5c 100644
    >> --- a/Documentation/virtual/kvm/api.txt
    >> +++ b/Documentation/virtual/kvm/api.txt
    >> @@ -1491,6 +1491,19 @@ following algorithm:
    >> Some guests configure the LINT1 NMI input to cause a panic, aiding in
    >> debugging.
    >>
    >> +4.65 KVMCLOCK_GUEST_PAUSED
    >> +
    >> +Capability: KVM_CAP_GUEST_PAUSED
    >> +Architechtures: Any that implement pvclocks (currently x86 only)
    >
    > typo: Architectures.
    >
    >
    >> +Type: vcpu ioctl
    >> +Parameters: None
    >> +Returns: 0 on success, -1 on error
    >> +
    >> +This signals to the host kernel that the specified guest is being paused by
    >> +userspace. The host will set a flag in the pvclock structure that is checked
    >> +from the soft lockup watchdog. This ioctl can be called during pause or
    >> +unpause.
    >> +
    >> 5. The kvm_run structure
    >>
    >> Application code obtains a pointer to the kvm_run structure by
    >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    >> index 14d6cad..c9cabba 100644
    >> --- a/arch/x86/kvm/x86.c
    >> +++ b/arch/x86/kvm/x86.c
    >> @@ -2056,6 +2056,7 @@ int kvm_dev_ioctl_check_extension(long ext)
    >> case KVM_CAP_X86_ROBUST_SINGLESTEP:
    >> case KVM_CAP_XSAVE:
    >> case KVM_CAP_ASYNC_PF:
    >> + case KVM_CAP_GUEST_PAUSED:
    >> case KVM_CAP_GET_TSC_KHZ:
    >> r = 1;
    >> break;
    >> @@ -2503,6 +2504,22 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu,
    >> return r;
    >> }
    >>
    >> +/*
    >> + * kvm_set_guest_paused() indicates to the guest kernel that it has been
    >> + * stopped by the hypervisor. This function will be called from the host only.
    >> + * EINVAL is returned when the host attempts to set the flag for a guest that
    >> + * does not support pv clocks.
    >> + */
    >> +static int kvm_set_guest_paused(struct kvm_vcpu *vcpu)
    >> +{
    >> + struct pvclock_vcpu_time_info *src = &vcpu->arch.hv_clock;
    >> + if (!vcpu->arch.time_page)
    >> + return -EINVAL;
    >> + src->flags |= PVCLOCK_GUEST_STOPPED;
    >> + mark_page_dirty(vcpu->kvm, vcpu->arch.time >> PAGE_SHIFT);
    >> + return 0;
    >> +}
    >
    > It should also call kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu), so
    > that the hv_clock is written to guest memory as soon as possible.
    >
    > Please fix the comments and rebase as soon as possible, it is annoying
    > that this feature is taking so long to be integrated.

    In addition:

    - Avi asked for a KVM_XXX_ naming pattern of the IOCTL, to align it
    with all the rest.
    - He even suggested KVM_CLOCK_CTRL, thus an extensible interface for
    passing flags via kvmclock on a per-vpcu basis.
    - As this is now supposed to be per-vcpu, constants should be called
    XXX_VCPU_STOPPED and no longer refer to "guest".

    Thanks,
    Jan


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