On Thu, Apr 30, 2009 at 03:24:07PM +0800, Dong, Eddie wrote:
>
>
> Move Double-Fault generation logic out of page fault
> exception generating function to cover more generic case.
>
> Signed-off-by: Eddie Dong <[email protected]>
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ab1fdac..51a8dad 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -162,12 +162,59 @@ void kvm_set_apic_base(struct kvm_vcpu *vcpu, u64 data)
> }
> EXPORT_SYMBOL_GPL(kvm_set_apic_base);
>
> +#define EXCPT_BENIGN 0
> +#define EXCPT_CONTRIBUTORY 1
> +#define EXCPT_PF 2
> +
> +static int exception_class(int vector)
> +{
> + if (vector == 14)
> + return EXCPT_PF;
> + else if (vector == 0 || (vector >= 10 && vector <= 13))
> + return EXCPT_CONTRIBUTORY;
> + else
> + return EXCPT_BENIGN;
> +}
> +
This makes double fault (8) benign exception. Surely not what you want.
> +static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
> + unsigned nr, bool has_error, u32 error_code)
> +{
> + u32 prev_nr;
> + int class1, class2;
> +
> + if (!vcpu->arch.exception.pending) {
> + vcpu->arch.exception.pending = true;
> + vcpu->arch.exception.has_error_code = has_error;
> + vcpu->arch.exception.nr = nr;
> + vcpu->arch.exception.error_code = error_code;
> + return;
> + }
> +
> + /* to check exception */
> + prev_nr = vcpu->arch.exception.nr;
> + class2 = exception_class(nr);
> + class1 = exception_class(prev_nr);
> + if ((class1 == EXCPT_CONTRIBUTORY && class2 == EXCPT_CONTRIBUTORY)
> + || (class1 == EXCPT_PF && class2 != EXCPT_BENIGN)) {
> + /* generate double fault per SDM Table 5-5 */
> + printk(KERN_DEBUG "kvm: double fault 0x%x on 0x%x\n",
> + prev_nr, nr);
> + vcpu->arch.exception.pending = true;
> + vcpu->arch.exception.has_error_code = 1;
> + vcpu->arch.exception.nr = DF_VECTOR;
> + vcpu->arch.exception.error_code = 0;
> + if (prev_nr == DF_VECTOR) {
> + /* triple fault -> shutdown */
> + set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
> + }
> + } else
> + printk(KERN_ERR "Exception 0x%x on 0x%x happens serially\n",
> + prev_nr, nr);
> +}
When two exceptions happens serially is is better to replace pending exception
with a new one. This way the first exception (that is lost) will be regenerated
when instruction will be re-executed.
--
Gleb.
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