From 94fe45da48f921d01d8ff02a0ad54ee9c326d7f0 Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Sun, 18 Oct 2009 13:24:44 +0200 Subject: [PATCH] KVM: x86: Fix guest single-stepping while interruptible Commit 705c5323 opened the doors of hell by unconditionally injecting single-step flags as long as guest_debug signaled this. This doesn't work when the guest branches into some interrupt or exception handler and triggers a vmexit with flag reloading. Fix it by saving cs:rip when user space requests single-stepping and restricting the trace flag injection to this guest code position. Signed-off-by: Jan Kiszka Signed-off-by: Marcelo Tosatti --- arch/x86/include/asm/kvm_host.h | 4 ++++ arch/x86/kvm/x86.c | 47 ++++++++++++++++++++++++----------------- 2 files changed, 32 insertions(+), 19 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 36f3b53f5c27..2536fbd85b3a 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -371,6 +371,10 @@ struct kvm_vcpu_arch { u64 mcg_status; u64 mcg_ctl; u64 *mce_banks; + + /* used for guest single stepping over the given code position */ + u16 singlestep_cs; + unsigned long singlestep_rip; }; struct kvm_mem_alias { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bb842db3ee7c..13f30aac460b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -235,25 +235,6 @@ bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl) } EXPORT_SYMBOL_GPL(kvm_require_cpl); -unsigned long kvm_get_rflags(struct kvm_vcpu *vcpu) -{ - unsigned long rflags; - - rflags = kvm_x86_ops->get_rflags(vcpu); - if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) - rflags &= ~(unsigned long)(X86_EFLAGS_TF | X86_EFLAGS_RF); - return rflags; -} -EXPORT_SYMBOL_GPL(kvm_get_rflags); - -void kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) -{ - if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) - rflags |= X86_EFLAGS_TF | X86_EFLAGS_RF; - kvm_x86_ops->set_rflags(vcpu, rflags); -} -EXPORT_SYMBOL_GPL(kvm_set_rflags); - /* * Load the pae pdptrs. Return true is they are all valid. */ @@ -4565,6 +4546,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, vcpu->arch.switch_db_regs = (vcpu->arch.dr7 & DR7_BP_EN_MASK); } + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { + vcpu->arch.singlestep_cs = + get_segment_selector(vcpu, VCPU_SREG_CS); + vcpu->arch.singlestep_rip = kvm_rip_read(vcpu); + } + /* * Trigger an rflags update that will inject or remove the trace * flags. @@ -5031,6 +5018,28 @@ int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu) return kvm_x86_ops->interrupt_allowed(vcpu); } +unsigned long kvm_get_rflags(struct kvm_vcpu *vcpu) +{ + unsigned long rflags; + + rflags = kvm_x86_ops->get_rflags(vcpu); + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) + rflags &= ~(unsigned long)(X86_EFLAGS_TF | X86_EFLAGS_RF); + return rflags; +} +EXPORT_SYMBOL_GPL(kvm_get_rflags); + +void kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) +{ + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP && + vcpu->arch.singlestep_cs == + get_segment_selector(vcpu, VCPU_SREG_CS) && + vcpu->arch.singlestep_rip == kvm_rip_read(vcpu)) + rflags |= X86_EFLAGS_TF | X86_EFLAGS_RF; + kvm_x86_ops->set_rflags(vcpu, rflags); +} +EXPORT_SYMBOL_GPL(kvm_set_rflags); + EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault); -- 2.11.0