Re: [PATCH] target/arm: Don't get MDCR_EL2 in pmu_counter_enabled() before checking ARM_FEATURE_PMU

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

On 2/8/24 05:33, Peter Maydell wrote:
> It doesn't make sense to read the value of MDCR_EL2 on a non-A-profile
> CPU, and in fact if you try to do it we will assert:
> 
> #6  0x00007ffff4b95e96 in __GI___assert_fail
>      (assertion=0x5555565a8c70 "!arm_feature(env, ARM_FEATURE_M)",
> file=0x5555565a6e5c "../../target/arm/helper.c", line=12600,
> function=0x5555565a9560 <__PRETTY_FUNCTION__.0>
> "arm_security_space_below_el3") at ./assert/assert.c:101
> #7  0x0000555555ebf412 in arm_security_space_below_el3
> (env=0x555557bc8190) at ../../target/arm/helper.c:12600
> #8  0x0000555555ea6f89 in arm_is_el2_enabled (env=0x555557bc8190) at
> ../../target/arm/cpu.h:2595
> #9  0x0000555555ea942f in arm_mdcr_el2_eff (env=0x555557bc8190) at
> ../../target/arm/internals.h:1512
> 
> We might call pmu_counter_enabled() on an M-profile CPU (for example
> from the migration pre/post hooks in machine.c); this should always
> return false because these CPUs don't set ARM_FEATURE_PMU.
> 
> Avoid the assertion by not calling arm_mdcr_el2_eff() before we
> have done the early return for "PMU not present".
> 
> This fixes an assertion failure if you try to do a loadvm or
> savevm for an M-profile board.
> 
> Cc:qemu-stable@nongnu.org
> Resolves:https://gitlab.com/qemu-project/qemu/-/issues/2155
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/arm/helper.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)

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

r~