Re: [PATCH 3/9] KVM: s390: pv: Add query interface

Thomas Huth
2022-02-23T11:30:44Z

On 23/02/2022 10.20, Janosch Frank wrote:
> Some of the query information is already available via sysfs but
> having a IOCTL makes the information easier to retrieve.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
> arch/s390/kvm/kvm-s390.c | 47 ++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/kvm.h | 23 ++++++++++++++++++++
> 2 files changed, 70 insertions(+)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index faa85397b6fb..837f898ad2ff 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2217,6 +2217,34 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
> return r;
> }
>
> +static int kvm_s390_handle_pv_info(struct kvm_s390_pv_info *info)
> +{
> + u32 len;
> +
> + switch (info->header.id) {
> + case KVM_PV_INFO_VM: {
> + len = sizeof(info->header) + sizeof(info->vm);
> +
> + if (info->header.len < len)
> + return -EINVAL;
> +
> + memcpy(info->vm.inst_calls_list,
> + uv_info.inst_calls_list,
> + sizeof(uv_info.inst_calls_list));
> +
> + /* It's max cpuidm not max cpus so it's off by one */
> + info->vm.max_cpus = uv_info.max_guest_cpu_id + 1;
> + info->vm.max_guests = uv_info.max_num_sec_conf;
> + info->vm.max_guest_addr = uv_info.max_sec_stor_addr;
> + info->vm.feature_indication = uv_info.uv_feature_indications;
> +
> + return 0;
> + }
> + default:
> + return -EINVAL;
> + }
> +}
> +
> static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
> {
> int r = 0;
> @@ -2353,6 +2381,25 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
> cmd->rc, cmd->rrc);
> break;
> }
> + case KVM_PV_INFO: {
> + struct kvm_s390_pv_info info = {};
> +
> + if (copy_from_user(&info, argp, sizeof(info.header)))
> + return -EFAULT;
> +
> + if (info.header.len < sizeof(info.header))
> + return -EINVAL;
> +
> + r = kvm_s390_handle_pv_info(&info);
> + if (r)
> + return r;
> +
> + r = copy_to_user(argp, &info, sizeof(info));

sizeof(info) is currently OK ... but this might break if somebody later
extends the kvm_s390_pv_info struct, I guess? ==> Maybe also better use
sizeof(info->header) + sizeof(info->vm) here, too? Or let
kvm_s390_handle_pv_info() return the amount of bytes that should be copied here?

Thomas

> + if (r)
> + return -EFAULT;
> + return 0;
> + }
> default:
> r = -ENOTTY;
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index dbc550bbd9fa..96fceb204a92 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1642,6 +1642,28 @@ struct kvm_s390_pv_unp {
> __u64 tweak;
> };
>
> +enum pv_cmd_info_id {
> + KVM_PV_INFO_VM,
> +};
> +
> +struct kvm_s390_pv_info_vm {
> + __u64 inst_calls_list[4];
> + __u64 max_cpus;
> + __u64 max_guests;
> + __u64 max_guest_addr;
> + __u64 feature_indication;
> +};
> +
> +struct kvm_s390_pv_info_header {
> + __u32 id;
> + __u32 len;
> +};
> +
> +struct kvm_s390_pv_info {
> + struct kvm_s390_pv_info_header header;
> + struct kvm_s390_pv_info_vm vm;
> +};
> +
> enum pv_cmd_id {
> KVM_PV_ENABLE,
> KVM_PV_DISABLE,
> @@ -1650,6 +1672,7 @@ enum pv_cmd_id {
> KVM_PV_VERIFY,
> KVM_PV_PREP_RESET,
> KVM_PV_UNSHARE_ALL,
> + KVM_PV_INFO,
> };
>
> struct kvm_pv_cmd {