Hi Dave,
On 18/02/2019 19:52, Dave Martin wrote:
> Now that all the pieces are in place, this patch offers a new flag
> KVM_ARM_VCPU_SVE that userspace can pass to KVM_ARM_VCPU_INIT to
> turn on SVE for the guest, on a per-vcpu basis.
>
> As part of this, support for initialisation and reset of the SVE
> vector length set and registers is added in the appropriate places.
> Allocation SVE registers is deferred until kvm_arm_vcpu_finalize(),
> by which time the size of the registers is known.
>
> Setting the vector lengths supported by the vcpu is considered
> configuration of the emulated hardware rather than runtime
> configuration, so no support is offered for changing the vector
> lengths of an existing vcpu across reset.
>
> Signed-off-by: Dave Martin <Dave.Martin at arm.com>
>
> ---
>
> Changes since v4:
>
> * Pull out vcpu_sve_state_size(), for use earlier in the series.
>
> * Remove unnecessary vcpu->arch.sve_vqs[], and clamp maximum guest
> vector length to 256 bytes for forwards compatibility.
>
> (See "KVM: arm64/sve: Add pseudo-register for the guest's vector
> lengths".)
>
> * Minor tidyups to make some checks less verbose.
> ---
> arch/arm64/include/asm/kvm_host.h | 2 +-
> arch/arm64/include/uapi/asm/kvm.h | 1 +
> arch/arm64/kvm/reset.c | 70 ++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 71 insertions(+), 2 deletions(-)
>
[...]
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 7ff1bd4..6963b7e 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -102,6 +102,7 @@ struct kvm_regs {
> #define KVM_ARM_VCPU_EL1_32BIT 1 /* CPU running a 32bit VM */
> #define KVM_ARM_VCPU_PSCI_0_2 2 /* CPU uses PSCI v0.2 */
> #define KVM_ARM_VCPU_PMU_V3 3 /* Support guest PMUv3 */
> +#define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */
>
> struct kvm_vcpu_init {
> __u32 target;
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 1379fb2..e67cd2e 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
[...]
> @@ -98,11 +100,69 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> return r;
> }
>
> +static int kvm_reset_sve(struct kvm_vcpu *vcpu)
> +{
> + if (!system_supports_sve())
> + return -EINVAL;
> +
> + /* If resetting an already-configured vcpu, just zero the SVE regs: */
> + if (vcpu->arch.sve_state) {
> + size_t size = vcpu_sve_state_size(vcpu);
> +
> + if (!size || WARN_ON(!vcpu_has_sve(vcpu)))
> + return -EINVAL;
> +
> + memset(vcpu->arch.sve_state, 0, size);
> + return 0;
> + }
> +
> + if (WARN_ON(!sve_vl_valid(sve_max_vl)))
> + return -EINVAL;
> +
> + /* If the full set of host vector lengths cannot be used, give up: */
> + if (sve_max_virtualisable_vl < sve_max_vl)
> + return -EINVAL;
> +
> + /* Default to the set of vector lengths supported by the host */
> + vcpu->arch.sve_max_vl = sve_max_vl;
> +
> + /*
> + * The get_sve_reg()/set_sve_reg() ioctl interface will need
> + * to be extended with multiple register slice support in
> + * order to support vector lengths greater than
> + * SVE_VL_ARCH_MAX:
> + */
> + if (WARN_ONCE(vcpu->arch.sve_max_vl > SVE_VL_ARCH_MAX,
> + "KVM: SVE vector length for guests limited to %d bytes\n",
> + SVE_VL_ARCH_MAX))
> + vcpu->arch.sve_max_vl = SVE_VL_ARCH_MAX;
> +
> + /*
> + * Userspace can still customize the vector lengths by writing
> + * KVM_REG_ARM64_SVE_VLS. Allocation is deferred until
> + * kvm_arm_vcpu_finalize(), which freezes the configuration.
> + */
> + vcpu->arch.flags |= KVM_ARM64_GUEST_HAS_SVE;
> +
> + return 0;
> +}
> +
> int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu)
> {
> if (likely(kvm_arm_vcpu_finalized(vcpu)))
> return 0;
>
> + if (vcpu_has_sve(vcpu)) {
> + size_t size = vcpu_sve_state_size(vcpu);
> +
> + if (!size)
> + return -EINVAL;
> +
> + vcpu->arch.sve_state = kzalloc(size, GFP_KERNEL);
We should probably free this in kvm_arch_vcpu_free().
Cheers,
--
Julien Thierry
