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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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