On Mon, Feb 15, 2010 at 03:53:04PM +0100, Jan Kiszka wrote: > We intercept #BP while in guest debugging mode. As VM exits due to > intercepted exceptions do not necessarily come with valid > idt_vectoring, we have to update event_exit_inst_len explicitly in such > cases. At least in the absence of migration, this ensures that > re-injections of #BP will find and use the correct instruction length. > Thinking about it some more. Why do we exit to userspace at all if we intercept wrong #DB? It seams to me not wise to have ability to inject exceptions from userspace. Exceptions generation mechanism is a part of CPU and we shouldn't outsource part of CPU functionality to userspace. > Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> > --- > > Changes in v2: > - added comments > > arch/x86/kvm/vmx.c | 13 +++++++++++++ > 1 files changed, 13 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index f82b072..14873b9 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -2775,6 +2775,12 @@ static int handle_rmode_exception(struct kvm_vcpu *vcpu, > kvm_queue_exception(vcpu, vec); > return 1; > case BP_VECTOR: > + /* > + * Update instruction length as we may reinject the exception > + * from user space while in guest debugging mode. > + */ > + to_vmx(vcpu)->vcpu.arch.event_exit_inst_len = > + vmcs_read32(VM_EXIT_INSTRUCTION_LEN); > if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) > return 0; > /* fall through */ > @@ -2897,6 +2903,13 @@ static int handle_exception(struct kvm_vcpu *vcpu) > kvm_run->debug.arch.dr7 = vmcs_readl(GUEST_DR7); > /* fall through */ > case BP_VECTOR: > + /* > + * Update instruction length as we may reinject #BP from > + * user space while in guest debugging mode. Reading it for > + * #DB as well causes no harm, it is not used in that case. > + */ > + vmx->vcpu.arch.event_exit_inst_len = > + vmcs_read32(VM_EXIT_INSTRUCTION_LEN); > kvm_run->exit_reason = KVM_EXIT_DEBUG; > kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip; > kvm_run->debug.arch.exception = ex_no; -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
