On Fri, May 08, 2009 at 04:27:28PM +0800, Dong, Eddie wrote:
> Gleb Natapov wrote:
> >> +
> >> +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.
>
> double fault fall into neither of above class per SDM. But it should be
> checked earlier than generating DB fault. See new updated.
> >> + /* 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.
>
> Do you want it to be covered for now? For exception, it is easy but for IRQ,
> it needs to be pushed back.
>
Yes I want it to be covered now otherwise any serial exception generates
flood of "Exception happens serially" messages. This function does not
handle IRQ so no problem there.
> Thx, eddie
>
>
>
> 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..d0e75a2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -162,12 +162,60 @@ 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;
> +}
> +
> +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;
> + if (prev_nr == DF_VECTOR) {
> + /* triple fault -> shutdown */
> + set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
> + return;
> + }
> + class1 = exception_class(prev_nr);
> + class2 = exception_class(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 = true;
> + vcpu->arch.exception.nr = DF_VECTOR;
> + vcpu->arch.exception.error_code = 0;
> + } else
> + printk(KERN_ERR "Exception 0x%x on 0x%x happens serially\n",
> + prev_nr, nr);
> +}
> +
> void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr)
> {
> - WARN_ON(vcpu->arch.exception.pending);
> - vcpu->arch.exception.pending = true;
> - vcpu->arch.exception.has_error_code = false;
> - vcpu->arch.exception.nr = nr;
> + kvm_multiple_exception(vcpu, nr, false, 0);
> }
> EXPORT_SYMBOL_GPL(kvm_queue_exception);
>
> @@ -176,18 +224,6 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu,
> unsigned long addr,
> {
> ++vcpu->stat.pf_guest;
>
> - if (vcpu->arch.exception.pending) {
> - if (vcpu->arch.exception.nr == PF_VECTOR) {
> - printk(KERN_DEBUG "kvm: inject_page_fault:"
> - " double fault 0x%lx\n", addr);
> - vcpu->arch.exception.nr = DF_VECTOR;
> - vcpu->arch.exception.error_code = 0;
> - } else if (vcpu->arch.exception.nr == DF_VECTOR) {
> - /* triple fault -> shutdown */
> - set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
> - }
> - return;
> - }
> vcpu->arch.cr2 = addr;
> kvm_queue_exception_e(vcpu, PF_VECTOR, error_code);
> }
> @@ -200,11 +236,7 @@ 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);
> - vcpu->arch.exception.pending = true;
> - vcpu->arch.exception.has_error_code = true;
> - vcpu->arch.exception.nr = nr;
> - vcpu->arch.exception.error_code = error_code;
> + kvm_multiple_exception(vcpu, nr, true, error_code);
> }
> EXPORT_SYMBOL_GPL(kvm_queue_exception_e);
>
--
Gleb.
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