[PATCH v5 03/10] KVM: s390: pv: Add query interface

Janosch Frank
2022-05-16T09:09:46Z

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 | 76 ++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 25 +++++++++++++
2 files changed, 101 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 76ad6408cb2c..5859f243d287 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2224,6 +2224,42 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
return r;
}

+/*
+ * Here we provide user space with a direct interface to query UV
+ * related data like UV maxima and available features as well as
+ * feature specific data.
+ *
+ * To facilitate future extension of the data structures we'll try to
+ * write data up to the maximum requested length.
+ */
+static ssize_t kvm_s390_handle_pv_info(struct kvm_s390_pv_info *info)
+{
+ ssize_t len_min;
+
+ switch (info->header.id) {
+ case KVM_PV_INFO_VM: {
+ len_min = sizeof(info->header) + sizeof(info->vm);
+
+ if (info->header.len_max < len_min)
+ return -EINVAL;
+
+ memcpy(info->vm.inst_calls_list,
+ uv_info.inst_calls_list,
+ sizeof(uv_info.inst_calls_list));
+
+ /* It's max cpuid 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 len_min;
+ }
+ default:
+ return -EINVAL;
+ }
+}
+
static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
{
int r = 0;
@@ -2360,6 +2396,46 @@ 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 = {};
+ ssize_t data_len;
+
+ /*
+ * No need to check the VM protection here.
+ *
+ * Maybe user space wants to query some of the data
+ * when the VM is still unprotected. If we see the
+ * need to fence a new data command we can still
+ * return an error in the info handler.
+ */
+
+ r = -EFAULT;
+ if (copy_from_user(&info, argp, sizeof(info.header)))
+ break;
+
+ r = -EINVAL;
+ if (info.header.len_max < sizeof(info.header))
+ break;
+
+ data_len = kvm_s390_handle_pv_info(&info);
+ if (data_len < 0) {
+ r = data_len;
+ break;
+ }
+ /*
+ * If a data command struct is extended (multiple
+ * times) this can be used to determine how much of it
+ * is valid.
+ */
+ info.header.len_written = data_len;
+
+ r = -EFAULT;
+ if (copy_to_user(argp, &info, data_len))
+ break;
+
+ r = 0;
+ break;
+ }
default:
r = -ENOTTY;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6a184d260c7f..8ac9de7d1386 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1653,6 +1653,30 @@ 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_max;
+ __u32 len_written;
+ __u32 reserved;
+};
+
+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,
@@ -1661,6 +1685,7 @@ enum pv_cmd_id {
KVM_PV_VERIFY,
KVM_PV_PREP_RESET,
KVM_PV_UNSHARE_ALL,
+ KVM_PV_INFO,
};

struct kvm_pv_cmd {
--
2.34.1