> On 14 Oct 2020, at 12:35, Andrew Cooper <andrew.coop...@citrix.com> wrote:
>
> On 14/10/2020 11:41, Bertrand Marquis wrote:
>> When a Cortex A57 processor is affected by CPU errata 832075, a guest
>> not implementing the workaround for it could deadlock the system.
>> Add a warning during boot informing the user that only trusted guests
>> should be executed on the system.
>> An equivalent warning is already given to the user by KVM on cores
>> affected by this errata.
>>
>> Signed-off-by: Bertrand Marquis <bertrand.marq...@arm.com>
>> ---
>> xen/arch/arm/cpuerrata.c | 21 +++++++++++++++++++++
>> 1 file changed, 21 insertions(+)
>>
>> diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
>> index 6c09017515..8f9ab6dde1 100644
>> --- a/xen/arch/arm/cpuerrata.c
>> +++ b/xen/arch/arm/cpuerrata.c
>> @@ -240,6 +240,26 @@ static int enable_ic_inv_hardening(void *data)
>>
>> #endif
>>
>> +#ifdef CONFIG_ARM64_ERRATUM_832075
>> +
>> +static int warn_device_load_acquire_errata(void *data)
>> +{
>> + static bool warned = false;
>> +
>> + if ( !warned )
>> + {
>> + warning_add("This CPU is affected by the errata 832075.\n"
>> + "Guests without required CPU erratum workarounds\n"
>> + "can deadlock the system!\n"
>> + "Only trusted guests should be used on this system.\n");
>> + warned = true;
>
> This is an antipattern, which probably wants fixing elsewhere as well.
>
> warning_add() is __init. It's not legitimate to call from a non-init
> function, and a less useless build system would have modpost to object.
>
> The ARM_SMCCC_ARCH_WORKAROUND_1 instance asserts based on system state,
> but this provides no safety at all.
>
>
> What warning_add() actually does is queue messages for some point near
> the end of boot. It's not clear that this is even a clever thing to do.
>
> I'm very tempted to suggest a blanket change to printk_once().
If this is needed then this could be done in an other serie ?
Would be good to keep this patch as purely handling the errata.
Regards
Bertrand
>
> ~Andrew
>
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +#endif
>> +
>> #ifdef CONFIG_ARM_SSBD
>>
>> enum ssbd_state ssbd_state = ARM_SSBD_RUNTIME;
>> @@ -419,6 +439,7 @@ static const struct arm_cpu_capabilities arm_errata[] = {
>> .capability = ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE,
>> MIDR_RANGE(MIDR_CORTEX_A57, 0x00,
>> (1 << MIDR_VARIANT_SHIFT) | 2),
>> + .enable = warn_device_load_acquire_errata,
>> },
>> #endif
>> #ifdef CONFIG_ARM64_ERRATUM_834220
