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    SubjectRe: [PATCH 03/10] KVM: SVM: Move nested INTR #vmexit into preemtible code
    On Wed, Oct 07, 2009 at 04:31:21PM +0200, Joerg Roedel wrote:
    > This patch makes use of the KVM_REQ_VMEXIT to move the
    > emulation of #vmexit(INTR) out of non-preemptible code.
    >
    > Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    > ---
    > arch/x86/kvm/svm.c | 18 ++++++++++++++++--
    > 1 files changed, 16 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
    > index b6ce1a9..7015680 100644
    > --- a/arch/x86/kvm/svm.c
    > +++ b/arch/x86/kvm/svm.c
    > @@ -1379,8 +1379,14 @@ static inline int nested_svm_intr(struct vcpu_svm *svm)
    >
    > svm->vmcb->control.exit_code = SVM_EXIT_INTR;
    >
    > - if (nested_svm_exit_handled(svm)) {
    > - nsvm_printk("VMexit -> INTR\n");
    > + if (svm->nested.intercept & 1ULL) {
    > + /*
    > + * The #vmexit can't be emulated here directly because this
    > + * code path runs with irqs and preemtion disabled and a
    > + * #vmexit emulation might sleep. Only set the request bit for
    > + * the #vmexit here.
    > + */
    > + set_bit(KVM_REQ_VMEXIT, &svm->vcpu.requests);
    > return 1;
    > }

    What if you keep this internal to SVM? Proceed to svm_vcpu_run and
    return, do the emulation on the exit handler.

    Then there's no need for the request bit (VMX does that, see
    vmx_vcpu_run).



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