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    Subject[PATCH 3.14 10/84] arm64: KVM: Disable virtual timer even if the guest is not using it
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Marc Zyngier <marc.zyngier@arm.com>

    commit c4cbba9fa078f55d9f6d081dbb4aec7cf969e7c7 upstream.

    When running a guest with the architected timer disabled (with QEMU and
    the kernel_irqchip=off option, for example), it is important to make
    sure the timer gets turned off. Otherwise, the guest may try to
    enable it anyway, leading to a screaming HW interrupt.

    The fix is to unconditionally turn off the virtual timer on guest
    exit.

    Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
    Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/arm64/kvm/hyp.S | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/arch/arm64/kvm/hyp.S
    +++ b/arch/arm64/kvm/hyp.S
    @@ -485,8 +485,6 @@ CPU_BE( rev w5, w5 )
    mrs x3, cntv_ctl_el0
    and x3, x3, #3
    str w3, [x0, #VCPU_TIMER_CNTV_CTL]
    - bic x3, x3, #1 // Clear Enable
    - msr cntv_ctl_el0, x3

    isb

    @@ -494,6 +492,9 @@ CPU_BE( rev w5, w5 )
    str x3, [x0, #VCPU_TIMER_CNTV_CVAL]

    1:
    + // Disable the virtual timer
    + msr cntv_ctl_el0, xzr
    +
    // Allow physical timer/counter access for the host
    mrs x2, cnthctl_el2
    orr x2, x2, #3



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