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    Subject[PATCH 3.14 033/238] arm/arm64: KVM: Complete WFI/WFE instructions
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Christoffer Dall <christoffer.dall@linaro.org>

    commit 05e0127f9e362b36aa35f17b1a3d52bca9322a3a upstream.

    The architecture specifies that when the processor wakes up from a WFE
    or WFI instruction, the instruction is considered complete, however we
    currrently return to EL1 (or EL0) at the WFI/WFE instruction itself.

    While most guests may not be affected by this because their local
    exception handler performs an exception returning setting the event bit
    or with an interrupt pending, some guests like UEFI will get wedged due
    this little mishap.

    Simply skip the instruction when we have completed the emulation.

    Acked-by: Marc Zyngier <marc.zyngier@arm.com>
    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/arm/kvm/handle_exit.c | 2 ++
    arch/arm64/kvm/handle_exit.c | 2 ++
    2 files changed, 4 insertions(+)

    --- a/arch/arm/kvm/handle_exit.c
    +++ b/arch/arm/kvm/handle_exit.c
    @@ -89,6 +89,8 @@ static int kvm_handle_wfx(struct kvm_vcp
    else
    kvm_vcpu_block(vcpu);

    + kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
    +
    return 1;
    }

    --- a/arch/arm64/kvm/handle_exit.c
    +++ b/arch/arm64/kvm/handle_exit.c
    @@ -62,6 +62,8 @@ static int kvm_handle_wfx(struct kvm_vcp
    else
    kvm_vcpu_block(vcpu);

    + kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
    +
    return 1;
    }




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