From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 21 Jan 2019 15:24:27 +0100 From: Greg KH Subject: Re: [PATCH v2] KVM: x86: Fix single-step debugging Message-ID: <20190121142427.GA26671@kroah.com> References: <1548074920-10651-1-git-send-email-alex.popov@linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1548074920-10651-1-git-send-email-alex.popov@linux.com> To: Alexander Popov Cc: Paolo Bonzini , Radim Krcmar , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Nadav Amit , Andy Lutomirski , Stefan Hajnoczi , H Peter Anvin , x86@kernel.org, kvm@vger.kernel.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org List-ID: On Mon, Jan 21, 2019 at 03:48:40PM +0300, Alexander Popov wrote: > 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 > --- > arch/x86/kvm/x86.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.