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? ;-)
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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