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Date: Mon, 21 Jan 2019 15:24:27 +0100
From: Greg KH <>
To: Alexander Popov <>
Cc: Paolo Bonzini <>, Radim Krcmar <>,
	Thomas Gleixner <>,
	Ingo Molnar <>, Borislav Petkov <>,
	Nadav Amit <>,
	Andy Lutomirski <>,
	Stefan Hajnoczi <>,
	H Peter Anvin <>,,,,
Subject: Re: [PATCH v2] KVM: x86: Fix single-step debugging

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:
for how to do this properly.


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