| From 5cc244a20b86090c087073c124284381cdf47234 Mon Sep 17 00:00:00 2001 |
| From: Alexander Popov <alex.popov@linux.com> |
| Date: Mon, 21 Jan 2019 15:48:40 +0300 |
| Subject: KVM: x86: Fix single-step debugging |
| |
| From: Alexander Popov <alex.popov@linux.com> |
| |
| commit 5cc244a20b86090c087073c124284381cdf47234 upstream. |
| |
| The single-step debugging of KVM guests on x86 is broken: if we run |
| gdb 'stepi' command at the breakpoint when the guest interrupts are |
| enabled, RIP always jumps to native_apic_mem_write(). Then other |
| nasty effects follow. |
| |
| Long investigation showed that on Jun 7, 2017 the |
| commit c8401dda2f0a00cd25c0 ("KVM: x86: fix singlestepping over syscall") |
| introduced the kvm_run.debug corruption: kvm_vcpu_do_singlestep() can |
| be called without X86_EFLAGS_TF set. |
| |
| Let's fix it. Please consider that for -stable. |
| |
| Signed-off-by: Alexander Popov <alex.popov@linux.com> |
| Cc: stable@vger.kernel.org |
| Fixes: c8401dda2f0a00cd25c0 ("KVM: x86: fix singlestepping over syscall") |
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/x86/kvm/x86.c | 3 +-- |
| 1 file changed, 1 insertion(+), 2 deletions(-) |
| |
| --- a/arch/x86/kvm/x86.c |
| +++ b/arch/x86/kvm/x86.c |
| @@ -5923,8 +5923,7 @@ restart: |
| toggle_interruptibility(vcpu, ctxt->interruptibility); |
| vcpu->arch.emulate_regs_need_sync_to_vcpu = false; |
| kvm_rip_write(vcpu, ctxt->eip); |
| - if (r == EMULATE_DONE && |
| - (ctxt->tf || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))) |
| + if (r == EMULATE_DONE && ctxt->tf) |
| kvm_vcpu_do_singlestep(vcpu, &r); |
| if (!ctxt->have_exception || |
| exception_type(ctxt->exception.vector) == EXCPT_TRAP) |
