Re: [PATCH v2 24/28] hw/intc/armv7m_nvic: Fix "return from inactive handler" check

[Richard Henderson <richard.henderson@linaro.org>]

On 11/19/20 3:56 PM, Peter Maydell wrote:
> In commit 077d7449100d824a4 we added code to handle the v8M
> requirement that returns from NMI or HardFault forcibly deactivate
> those exceptions regardless of what interrupt the guest is trying to
> deactivate.  Unfortunately this broke the handling of the "illegal
> exception return because the returning exception number is not
> active" check for those cases.  In the pseudocode this test is done
> on the exception the guest asks to return from, but because our
> implementation was doing this in armv7m_nvic_complete_irq() after the
> new "deactivate NMI/HardFault regardless" code we ended up doing the
> test on the VecInfo for that exception instead, which usually meant
> failing to raise the illegal exception return fault.
> 
> In the case for "configurable exception targeting the opposite
> security state" we detected the illegal-return case but went ahead
> and deactivated the VecInfo anyway, which is wrong because that is
> the VecInfo for the other security state.
> 
> Rearrange the code so that we first identify the illegal return
> cases, then see if we really need to deactivate NMI or HardFault
> instead, and finally do the deactivation.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/intc/armv7m_nvic.c | 59 +++++++++++++++++++++++--------------------
>  1 file changed, 32 insertions(+), 27 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~