On 28/05/15 14:02, Christoffer Dall wrote:
> On Thu, May 28, 2015 at 10:27:14AM +0100, Marc Zyngier wrote:
>> On 14/05/15 12:25, Christoffer Dall wrote:
>>> On Fri, Mar 27, 2015 at 01:09:24PM +0000, Marc Zyngier wrote:
>>>> Add a new item to the feature set (ARM64_HAS_SYSREG_GIC_CPUIF)
>>>> to indicate that we have a system register GIC CPU interface
>>>>
>>>> This will help KVM switching to alternative instruction patching.
>>>>
>>>> Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
>>>> Acked-by: Will Deacon <will.deacon@xxxxxxx>
>>>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>>>> ---
>>>> arch/arm64/include/asm/cpufeature.h | 8 +++++++-
>>>> arch/arm64/kernel/cpufeature.c | 16 ++++++++++++++++
>>>> 2 files changed, 23 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>>>> index 6ae35d1..d9e57b5 100644
>>>> --- a/arch/arm64/include/asm/cpufeature.h
>>>> +++ b/arch/arm64/include/asm/cpufeature.h
>>>> @@ -23,8 +23,9 @@
>>>>
>>>> #define ARM64_WORKAROUND_CLEAN_CACHE 0
>>>> #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE 1
>>>> +#define ARM64_HAS_SYSREG_GIC_CPUIF 2
>>>>
>>>> -#define ARM64_NCAPS 2
>>>> +#define ARM64_NCAPS 3
>>>>
>>>> #ifndef __ASSEMBLY__
>>>>
>>>> @@ -37,6 +38,11 @@ struct arm64_cpu_capabilities {
>>>> u32 midr_model;
>>>> u32 midr_range_min, midr_range_max;
>>>> };
>>>> +
>>>> + struct { /* Feature register checking */
>>>> + u64 register_mask;
>>>> + u64 register_value;
>>>> + };
>>>> };
>>>> };
>>>>
>>>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>>>> index 3d9967e..b0bea2b3 100644
>>>> --- a/arch/arm64/kernel/cpufeature.c
>>>> +++ b/arch/arm64/kernel/cpufeature.c
>>>> @@ -22,7 +22,23 @@
>>>> #include <asm/cpu.h>
>>>> #include <asm/cpufeature.h>
>>>>
>>>> +static bool
>>>> +has_id_aa64pfr0_feature(const struct arm64_cpu_capabilities *entry)
>>>> +{
>>>> + u64 val;
>>>> +
>>>> + val = read_cpuid(id_aa64pfr0_el1);
>>>
>>> is this preferred compared to fishing it out of cpuinfo ?
>>
>> Probably for the moment, yes. At some point, we should be able to have a
>> consolidated set of features, consistent across all CPUs in the system.
>> Once we have that, we should revisit this detection mecanism.
>>
>>>> + return (val & entry->register_mask) == entry->register_value;
>>>> +}
>>>> +
>>>> static const struct arm64_cpu_capabilities arm64_features[] = {
>>>> + {
>>>> + .desc = "system register GIC CPU interface",
>>>> + .capability = ARM64_HAS_SYSREG_GIC_CPUIF,
>>>> + .matches = has_id_aa64pfr0_feature,
>>>> + .register_mask = (0xf << 24),
>>>> + .register_value = (1 << 24),
>>>
>>> I don't know if it's worth defining these masks in some header file.
>>> The only other place I could see them used was in head.S.
>>
>> Mark was looking at this a while ago. Maybe a task for a sleepless
>> night? ;-)
>>
>
> yeah, you can add this to the patch if it helps:
>
> Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Thanks. I'll look at getting these two patches in once the dependencies
are merged.
M.
--
Jazz is not dead. It just smells funny...
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