On 11/03/2015 15:44, James Hogan wrote:
> Now that the code is in place for KVM to support MIPS SIMD Architecutre
> (MSA) in MIPS guests, wire up the new KVM_CAP_MIPS_MSA capability.
>
> For backwards compatibility, the capability must be explicitly enabled
> in order to detect or make use of MSA from the guest.
>
> The capability is not supported if the hardware supports MSA vector
> partitioning, since the extra support cannot be tested yet and it
> extends the state that the userland program would have to save.
>
> Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx
> Cc: linux-api@xxxxxxxxxxxxxxx
> Cc: linux-doc@xxxxxxxxxxxxxxx
> Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
> ---
> Documentation/virtual/kvm/api.txt | 12 ++++++++++++
> arch/mips/kvm/mips.c | 24 ++++++++++++++++++++++++
> include/uapi/linux/kvm.h | 1 +
> 3 files changed, 37 insertions(+)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 47ddf0475211..97dd9ee69ca8 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3224,6 +3224,18 @@ done the KVM_REG_MIPS_FPR_* and KVM_REG_MIPS_FCR_* registers can be accessed
> Config5.FRE bits are accessible via the KVM API and also from the guest,
> depending on them being supported by the FPU.
>
> +6.10 KVM_CAP_MIPS_MSA
> +
> +Architectures: mips
> +Target: vcpu
> +Parameters: args[0] is reserved for future use (should be 0).
> +
> +This capability allows the use of the MIPS SIMD Architecture (MSA) by the guest.
> +It allows the Config3.MSAP bit to be set to enable the use of MSA by the guest.
> +Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be
> +accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from
> +the guest.
> +
> 7. Capabilities that can be enabled on VMs
> ------------------------------------------
>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 9319c4360285..3b3530f493eb 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -880,6 +880,15 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
> return -EINVAL;
> vcpu->arch.fpu_enabled = true;
> break;
> + case KVM_CAP_MIPS_MSA:
> + /*
> + * MSA vector partitioning not supported,
> + * see kvm_vm_ioctl_check_extension().
> + */
> + if (!cpu_has_msa || boot_cpu_data.msa_id & MSA_IR_WRPF)
> + return -EINVAL;
Perhaps you can call kvm_vm_ioctl_check_extension directly, outside the
switch (it's okay if it's called for a capability other than FPU and MSA)?
Apart from this nit,
Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Paolo
> + vcpu->arch.msa_enabled = true;
> + break;
> default:
> r = -EINVAL;
> break;
> @@ -1071,6 +1080,21 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_MIPS_FPU:
> r = !!cpu_has_fpu;
> break;
> + case KVM_CAP_MIPS_MSA:
> + /*
> + * We don't support MSA vector partitioning yet:
> + * 1) It would require explicit support which can't be tested
> + * yet due to lack of support in current hardware.
> + * 2) It extends the state that would need to be saved/restored
> + * by e.g. QEMU for migration.
> + *
> + * When vector partitioning hardware becomes available, support
> + * could be added by requiring a flag when enabling
> + * KVM_CAP_MIPS_MSA capability to indicate that userland knows
> + * to save/restore the appropriate extra state.
> + */
> + r = cpu_has_msa && !(boot_cpu_data.msa_id & MSA_IR_WRPF);
> + break;
> default:
> r = 0;
> break;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 98f6e5c653ff..5f859888e3ad 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -761,6 +761,7 @@ struct kvm_ppc_smmu_info {
> #define KVM_CAP_CHECK_EXTENSION_VM 105
> #define KVM_CAP_S390_USER_SIGP 106
> #define KVM_CAP_MIPS_FPU 107
> +#define KVM_CAP_MIPS_MSA 108
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
>
