KVM: arm64: pvtime: Ensure task delay accounting is enabled

Ensure we're actually accounting run_delay before we claim that we'll
expose it to the guest. If we're not, then we just pretend like steal
time isn't supported in order to avoid any confusion.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200622142710.18677-1-drjones@redhat.com

diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c
index 1e0f4c2..f7b52ce 100644 (file)
--- a/arch/arm64/kvm/pvtime.c
+++ b/arch/arm64/kvm/pvtime.c
@@ -3,6 +3,7 @@
 
 #include <linux/arm-smccc.h>
 #include <linux/kvm_host.h>
+#include <linux/sched/stat.h>
 
 #include <asm/kvm_mmu.h>
 #include <asm/pvclock-abi.h>
@@ -73,6 +74,11 @@ gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu)
        return base;
 }
 
+static bool kvm_arm_pvtime_supported(void)
+{
+       return !!sched_info_on();
+}
+
 int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu,
                            struct kvm_device_attr *attr)
 {
@@ -82,7 +88,8 @@ int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu,
        int ret = 0;
        int idx;
 
-       if (attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
+       if (!kvm_arm_pvtime_supported() ||
+           attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
                return -ENXIO;
 
        if (get_user(ipa, user))
@@ -110,7 +117,8 @@ int kvm_arm_pvtime_get_attr(struct kvm_vcpu *vcpu,
        u64 __user *user = (u64 __user *)attr->addr;
        u64 ipa;
 
-       if (attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
+       if (!kvm_arm_pvtime_supported() ||
+           attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
                return -ENXIO;
 
        ipa = vcpu->arch.steal.base;
@@ -125,7 +133,8 @@ int kvm_arm_pvtime_has_attr(struct kvm_vcpu *vcpu,
 {
        switch (attr->attr) {
        case KVM_ARM_VCPU_PVTIME_IPA:
-               return 0;
+               if (kvm_arm_pvtime_supported())
+                       return 0;
        }
        return -ENXIO;
 }