Re: [PATCH] target/arm: Don't migrate CPUARMState.features

[Philippe Mathieu-Daudé]

On 2/3/21 5:13 PM, Aaron Lindsay wrote:
> As feature flags are added or removed, the meanings of bits in the
> `features` field can change between QEMU versions, causing migration
> failures. Additionally, migrating the field is not useful because it is
> a constant function of the CPU being used.

Please don't bury patches within mailing list threads.

BTW you found yet another 13 years old problem :)
918f5dca18d ("target-arm: Extend feature flags to 64 bits")
aa941b94450 ("Savevm/loadvm bits for ARM core, the PXA2xx peripherals
and Spitz hardware.")

> 
> Signed-off-by: Aaron Lindsay <aaron@os.amperecomputing.com>
> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/machine.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/arm/machine.c b/target/arm/machine.c
> index c9e9fd0a12..7f2511b6ed 100644
> --- a/target/arm/machine.c
> +++ b/target/arm/machine.c
> @@ -834,7 +834,7 @@ const VMStateDescription vmstate_arm_cpu = {
>          VMSTATE_UINT64(env.exclusive_addr, ARMCPU),
>          VMSTATE_UINT64(env.exclusive_val, ARMCPU),
>          VMSTATE_UINT64(env.exclusive_high, ARMCPU),
> -        VMSTATE_UINT64(env.features, ARMCPU),
> +        VMSTATE_UNUSED(sizeof(uint64_t)),
>          VMSTATE_UINT32(env.exception.syndrome, ARMCPU),
>          VMSTATE_UINT32(env.exception.fsr, ARMCPU),
>          VMSTATE_UINT64(env.exception.vaddress, ARMCPU),
>