On 28/03/2015 23:27, Eugene Korenevsky wrote: > Emulate #DB generation on task switch if TSS.T is set according to Intel SDM. > The processor generates a debug exception after a task switch if the T flag of > the new task's TSS is set. This exception is generated after program control > has passed to the new task, and prior to the execution of the first > instruction > of that task. DR6.BT bit should be set to indicate this condition. > > Signed-off-by: Eugene Korenevsky <[email protected]> > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/emulate.c | 13 +++++++++++++ > arch/x86/kvm/vmx.c | 5 ----- > arch/x86/kvm/x86.c | 4 ++++ > 4 files changed, 18 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index a236e39..981e9ea 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -147,6 +147,7 @@ enum { > > #define DR6_BD (1 << 13) > #define DR6_BS (1 << 14) > +#define DR6_BT (1 << 15) > #define DR6_RTM (1 << 16) > #define DR6_FIXED_1 0xfffe0ff0 > #define DR6_INIT 0xffff0ff0 > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 3a494f3..4ef1c27 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -2783,6 +2783,19 @@ static int load_state_from_tss32(struct > x86_emulate_ctxt *ctxt, > ret = __load_segment_descriptor(ctxt, tss->gs, VCPU_SREG_GS, cpl, > X86_TRANSFER_TASK_SWITCH, NULL); > > + /* > + * The last thing to do is injecting #DB trap if TSS.T bit is set > + */ > + if (ret == X86EMUL_CONTINUE && tss->t) { > + ulong dr6; > + > + ctxt->ops->get_dr(ctxt, 6, &dr6); > + dr6 |= DR6_BT | DR6_FIXED_1 | DR6_RTM; > + ctxt->ops->set_dr(ctxt, 6, dr6); > + ctxt->have_exception = true; > + emulate_db(ctxt); > + } > + > return ret; > } > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index f7b20b4..d922fd8 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -5696,11 +5696,6 @@ static int handle_task_switch(struct kvm_vcpu *vcpu) > /* clear all local breakpoint enable flags */ > vmcs_writel(GUEST_DR7, vmcs_readl(GUEST_DR7) & ~0x155); > > - /* > - * TODO: What about debug traps on tss switch? > - * Are we supposed to inject them and update dr6? > - */ > - > return 1; > } > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index bd7a70b..66ac520 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6736,6 +6736,7 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 > tss_selector, int idt_index, > int ret; > > init_emulate_ctxt(vcpu); > + ctxt->have_exception = false;
Please instead add the statement to init_emulate_ctxt, and remove it from x86_emulate_instruction. > > ret = emulator_task_switch(ctxt, tss_selector, idt_index, reason, > has_error_code, error_code); > @@ -6745,6 +6746,9 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 > tss_selector, int idt_index, > > kvm_rip_write(vcpu, ctxt->eip); > kvm_set_rflags(vcpu, ctxt->eflags); > + /* Generate #DB trap if T bit is set in new TSS */ > + if (ctxt->have_exception && ctxt->exception.vector == DB_VECTOR) > + kvm_queue_exception(vcpu, DB_VECTOR); I think you should just call kvm_multiple_exception directly, because it's also possible that you'd have to inject a #TS exception here. Paolo > kvm_make_request(KVM_REQ_EVENT, vcpu); > return EMULATE_DONE; > } > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
