On Wed, Nov 11, 2009 at 05:29:48PM -0200, Marcelo Tosatti wrote:
> From: Joerg Roedel <joerg.roedel@xxxxxxx>
>
> The current KVM x86 exception code handles double and triple faults only for
> page fault exceptions. This patch extends this detection for every exception
> that gets queued for the guest.
>
> Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
> CC: Jan Kiszka <jan.kiszka@xxxxxx>
>
> Index: kvm/arch/x86/kvm/x86.c
> ===================================================================
> --- kvm.orig/arch/x86/kvm/x86.c
> +++ kvm/arch/x86/kvm/x86.c
> @@ -170,9 +170,21 @@ void kvm_set_apic_base(struct kvm_vcpu *
> }
> EXPORT_SYMBOL_GPL(kvm_set_apic_base);
>
> +static void handle_multiple_faults(struct kvm_vcpu *vcpu)
> +{
> + if (vcpu->arch.exception.nr != DF_VECTOR) {
> + vcpu->arch.exception.nr = DF_VECTOR;
> + vcpu->arch.exception.error_code = 0;
> + } else
> + set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
> +}
> +
Making #DF from two bening exceptions is very wrong.
> void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr)
> {
> - WARN_ON(vcpu->arch.exception.pending);
> + if (vcpu->arch.exception.pending) {
> + handle_multiple_faults(vcpu);
> + return;
> + }
> vcpu->arch.exception.pending = true;
> vcpu->arch.exception.has_error_code = false;
> vcpu->arch.exception.nr = nr;
> @@ -184,24 +196,6 @@ void kvm_inject_page_fault(struct kvm_vc
> {
> ++vcpu->stat.pf_guest;
>
> - if (vcpu->arch.exception.pending) {
> - switch(vcpu->arch.exception.nr) {
> - case DF_VECTOR:
> - /* triple fault -> shutdown */
> - set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
> - return;
> - case PF_VECTOR:
> - vcpu->arch.exception.nr = DF_VECTOR;
> - vcpu->arch.exception.error_code = 0;
> - return;
> - default:
> - /* replace previous exception with a new one in a hope
> - that instruction re-execution will regenerate lost
> - exception */
> - vcpu->arch.exception.pending = false;
> - break;
When exceptions are handled serially previous exception have to be
replaced by new one. Think about #PF during #DE. #PF should be handled first
before #DE can proceed.
> - }
> - }
> vcpu->arch.cr2 = addr;
> kvm_queue_exception_e(vcpu, PF_VECTOR, error_code);
> }
> @@ -214,7 +208,10 @@ EXPORT_SYMBOL_GPL(kvm_inject_nmi);
>
> void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
> {
> - WARN_ON(vcpu->arch.exception.pending);
> + if (vcpu->arch.exception.pending) {
> + handle_multiple_faults(vcpu);
> + return;
> + }
> vcpu->arch.exception.pending = true;
> vcpu->arch.exception.has_error_code = true;
> vcpu->arch.exception.nr = nr;
>
> --
--
Gleb.
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