[PATCH v2 4/4] KVM: selftests: Add arm64 coverage for steal time pid changes

[Dongli Zhang <dongli.zhang@oracle.com>]

The previous patch added the common steal_time_change_pid test with x86
support. Add the arm64 support so the same test also covers arm64.

Use KVM_ARM_VCPU_PVTIME_IPA to enable the steal time shared page from
userspace, and use the PV_TIME_ST SMCCC call in the guest to retrieve and
read that page.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
As I have access to only x86 and arm64 KVM hosts, I created and validated
the selftest on those two architectures only.

 tools/testing/selftests/kvm/Makefile.kvm      |  1 +
 .../selftests/kvm/steal_time_change_pid.c     | 54 +++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 036c28849f84..1de13c0017e4 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -205,6 +205,7 @@ TEST_GEN_PROGS_arm64 += guest_memfd_test
 TEST_GEN_PROGS_arm64 += mmu_stress_test
 TEST_GEN_PROGS_arm64 += rseq_test
 TEST_GEN_PROGS_arm64 += steal_time
+TEST_GEN_PROGS_arm64 += steal_time_change_pid
 
 TEST_GEN_PROGS_s390 = $(TEST_GEN_PROGS_COMMON)
 TEST_GEN_PROGS_s390 += s390/memop
diff --git a/tools/testing/selftests/kvm/steal_time_change_pid.c b/tools/testing/selftests/kvm/steal_time_change_pid.c
index 3c39594db398..12d4927d1c01 100644
--- a/tools/testing/selftests/kvm/steal_time_change_pid.c
+++ b/tools/testing/selftests/kvm/steal_time_change_pid.c
@@ -46,6 +46,60 @@ static void steal_time_enable(struct kvm_vcpu *vcpu)
 		     (ulong)st_gva | KVM_MSR_ENABLED);
 }
 
+#elif defined(__aarch64__)
+
+#define STEAL_TIME_SIZE	((sizeof(struct st_time) + 63) & ~63)
+
+#define PV_TIME_ST	0xc5000021
+
+struct st_time {
+	u32 rev;
+	u32 attr;
+	u64 st_time;
+};
+
+static void guest_code(void)
+{
+	struct arm_smccc_res res;
+	struct st_time *st;
+
+	do_smccc(PV_TIME_ST, 0, 0, 0, 0, 0, 0, 0, &res);
+	GUEST_ASSERT_NE(res.a0, -1);
+	GUEST_ASSERT_EQ(res.a0, (ulong)st_gva);
+
+	st = (struct st_time *)res.a0;
+	WRITE_ONCE(guest_stolen_time, READ_ONCE(st->st_time));
+	GUEST_SYNC(0);
+
+	WRITE_ONCE(guest_stolen_time, READ_ONCE(st->st_time));
+	GUEST_SYNC(1);
+
+	WRITE_ONCE(guest_stolen_time, READ_ONCE(st->st_time));
+	GUEST_DONE();
+}
+
+static bool steal_time_supported(struct kvm_vcpu *vcpu)
+{
+	struct kvm_device_attr dev = {
+		.group = KVM_ARM_VCPU_PVTIME_CTRL,
+		.attr = KVM_ARM_VCPU_PVTIME_IPA,
+	};
+
+	return !__vcpu_ioctl(vcpu, KVM_HAS_DEVICE_ATTR, &dev);
+}
+
+static void steal_time_enable(struct kvm_vcpu *vcpu)
+{
+	u64 st_ipa = (ulong)st_gva;
+	struct kvm_device_attr dev = {
+		.group = KVM_ARM_VCPU_PVTIME_CTRL,
+		.attr = KVM_ARM_VCPU_PVTIME_IPA,
+		.addr = (u64)&st_ipa,
+	};
+
+	vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
+}
+
 #else
 #error "steal_time_change_pid is not implemented on this architecture"
 #endif
-- 
2.43.7