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.
Alex
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