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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 <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Jan Kiszka 2009-10-18 13:24:44 +02:00 committed by Avi Kivity
parent ffde22ac53
commit 94fe45da48
2 changed files with 32 additions and 19 deletions
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4
arch/x86/include/asm/kvm_host.h
View File

@ -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 {

47
arch/x86/kvm/x86.c
View File

@ -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);