Re: [Qemu-devel] [PATCH v2] kvmclock: update system_time_msr address forcibly

[Roman Kagan]

On Fri, May 26, 2017 at 03:25:22PM +0300, Denis Plotnikov wrote:
> Do an update of system_time_msr address every time before reading
> the value of tsc_timestamp from guest's kvmclock page.
> 
> There is no other code paths which ensure that qemu has an up-to-date
> value of system_time_msr. So, force this update on guest's tsc_timestamp
> reading.
> 
> This bug causes effect on those nested setups which turn off TPR access
> interception for L2 guests and that access being intercepted by L0 doesn't
> show up in L1.
> Linux bootstrap initiate kvmclock before APIC initializing causing TPR access.
> That's why on L1 guests, having TPR interception turned on for L2, the effect
> of the bug is not revealed.
> 
> This patch fixes this problem by making sure it knows the correct
> system_time_msr address every time it is needed.
> 
> Signed-off-by: Denis Plotnikov <address@hidden>
> ---
>  hw/i386/kvm/clock.c | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Roman Kagan <address@hidden>