On Mon, Jul 15, 2013 at 6:32 PM, Alexander Graf <agraf@xxxxxxx> wrote:
>
> On 15.07.2013, at 14:56, Anup Patel wrote:
>
>> Hi Marc,
>>
>> On Mon, Jul 15, 2013 at 6:09 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>>> Hi Anup,
>>>
>>> On 15/07/13 12:46, Anup Patel wrote:
>>>> This patch allows us to have X-Gene guest VCPU when using
>>>> KVM arm64 on APM X-Gene host.
>>>>
>>>> We add KVM_ARM_TARGET_XGENE_V8 for X-Gene compatible guest VCPU
>>>> and we return KVM_ARM_TARGET_XGENE_V8 in kvm_target_cpu() when
>>>> running on X-Gene host.
>>>>
>>>> Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxx>
>>>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx>
>>>> ---
>>>> arch/arm64/include/uapi/asm/kvm.h | 3 ++-
>>>> arch/arm64/kvm/guest.c | 34 ++++++++++++++++++++++------------
>>>> arch/arm64/kvm/sys_regs_generic_v8.c | 3 +++
>>>> 3 files changed, 27 insertions(+), 13 deletions(-)
>>>>
>>>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>>>> index 5031f42..8194707 100644
>>>> --- a/arch/arm64/include/uapi/asm/kvm.h
>>>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>>>> @@ -55,8 +55,9 @@ struct kvm_regs {
>>>> #define KVM_ARM_TARGET_AEM_V8 0
>>>> #define KVM_ARM_TARGET_FOUNDATION_V8 1
>>>> #define KVM_ARM_TARGET_CORTEX_A57 2
>>>> +#define KVM_ARM_TARGET_XGENE_V8 3
>>>>
>>>> -#define KVM_ARM_NUM_TARGETS 3
>>>> +#define KVM_ARM_NUM_TARGETS 4
>>>>
>>>> /* KVM_ARM_SET_DEVICE_ADDR ioctl id encoding */
>>>> #define KVM_ARM_DEVICE_TYPE_SHIFT 0
>>>> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
>>>> index 2c3ff67..e99b0a5 100644
>>>> --- a/arch/arm64/kvm/guest.c
>>>> +++ b/arch/arm64/kvm/guest.c
>>>> @@ -207,19 +207,29 @@ int __attribute_const__ kvm_target_cpu(void)
>>>> unsigned long implementor = read_cpuid_implementor();
>>>> unsigned long part_number = read_cpuid_part_number();
>>>>
>>>> - if (implementor != ARM_CPU_IMP_ARM)
>>>> - return -EINVAL;
>>>> -
>>>> - switch (part_number) {
>>>> - case ARM_CPU_PART_AEM_V8:
>>>> - return KVM_ARM_TARGET_AEM_V8;
>>>> - case ARM_CPU_PART_FOUNDATION:
>>>> - return KVM_ARM_TARGET_FOUNDATION_V8;
>>>> - case ARM_CPU_PART_CORTEX_A57:
>>>> - /* Currently handled by the generic backend */
>>>> - return KVM_ARM_TARGET_CORTEX_A57;
>>>> + switch (implementor) {
>>>> + case ARM_CPU_IMP_ARM:
>>>> + switch (part_number) {
>>>> + case ARM_CPU_PART_AEM_V8:
>>>> + return KVM_ARM_TARGET_AEM_V8;
>>>> + case ARM_CPU_PART_FOUNDATION:
>>>> + return KVM_ARM_TARGET_FOUNDATION_V8;
>>>> + case ARM_CPU_PART_CORTEX_A57:
>>>> + return KVM_ARM_TARGET_CORTEX_A57;
>>>> + default:
>>>> + return -EINVAL;
>>>> + }
>>>> + break;
>>>> + case ARM_CPU_IMP_APM:
>>>> + switch (part_number) {
>>>> + case APM_CPU_PART_POTENZA:
>>>> + return KVM_ARM_TARGET_XGENE_V8;
>>>
>>> Why don't we have KVM_ARM_TARGET_XGENE_POTENZA (or something similar)
>>> instead? I don't expect all the X-Gene CPUs to be the same forever...
>>
>> OK, I will rename it to KVM_ARM_TARGET_XGENE_POTENZA.
>>
>> Does this mean that with every new ARM64 CPU we will have to add a new
>> target for KVM ARM64 ?
>
> Only for different core types, no? Any Cortex-A57 should still behave the same.
>
>> If so then I think the list of targets will grow very fast.
>>
>> I also realized that if we add a new target type in KVM ARM64 then we have
>> to also update KVMTOOL to use the new target else KVMTOOL fails to
>> recognize the target provided by KVM ARM64.
>
> Right. It might make sense to have a fetch mechanism for the host cpu part. So you can ask KVM for the host cpu type and pass that back in here.
>
>> Do you think we can have KVM_ARM_TARGET_xxx to represent a common
>> target for a family of CPUs from given ARM64 vendor?
>
> Anything that is compatible is compatible :). I don't know the product roadmaps for X-Gene cores, but you will want to make the field here as coarse grained as possible, while maintaining the guarantee that a guest still behaves the same.
Actually, I don't see X-Gene cores changing in-terms of register interface
available to EL1 and EL0 in near future. This is the reason why I had named
the target as KVM_ARM_TARGET_XGENE_V8.
My only concern in having a more specific target type (such as
KVM_ARM_TARGET_XGENE_POTENZA) is that we might unnecessarily
add new target types without any difference on KVM-side.
>
>
> Alex
>
--Anup
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
