KVM: s390: selftests: Add uc_skey VM test case

Add a test case manipulating s390 storage keys from within the ucontrol
VM.

Storage key instruction (ISKE, SSKE and RRBE) intercepts and
Keyless-subset facility are disabled on first use, where the skeys are
setup by KVM in non ucontrol VMs.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Link: https://lore.kernel.org/r/20241108091620.289406-1-schlameuss@linux.ibm.com
Acked-by: Janosch Frank <frankja@linux.ibm.com>
[frankja@linux.ibm.com: Fixed patch prefix]
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Message-ID: <20241108091620.289406-1-schlameuss@linux.ibm.com>

tools/testing/selftests/kvm/include/s390x/processor.h

@@ -32,4 +32,10 @@ static inline void cpu_relax(void)
 	barrier();
 }
 
+/* Get the instruction length */
+static inline int insn_length(unsigned char code)
+{
+	return ((((int)code + 64) >> 7) + 1) << 1;
+}
+
 #endif

tools/testing/selftests/kvm/s390x/ucontrol_test.c

@@ -79,6 +79,33 @@ asm("test_mem_asm:\n"
 	"	j	0b\n"
 );
 
+/* Test program manipulating storage keys */
+extern char test_skey_asm[];
+asm("test_skey_asm:\n"
+	"xgr	%r0, %r0\n"
+
+	"0:\n"
+	"	ahi	%r0,1\n"
+	"	st	%r1,0(%r5,%r6)\n"
+
+	"	iske	%r1,%r6\n"
+	"	ahi	%r0,1\n"
+	"	diag	0,0,0x44\n"
+
+	"	sske	%r1,%r6\n"
+	"	xgr	%r1,%r1\n"
+	"	iske	%r1,%r6\n"
+	"	ahi	%r0,1\n"
+	"	diag	0,0,0x44\n"
+
+	"	rrbe	%r1,%r6\n"
+	"	iske	%r1,%r6\n"
+	"	ahi	%r0,1\n"
+	"	diag	0,0,0x44\n"
+
+	"	j	0b\n"
+);
+
 FIXTURE(uc_kvm)
 {
 	struct kvm_s390_sie_block *sie_block;
@@ -298,8 +325,50 @@ static void uc_handle_exit_ucontrol(FIXTURE_DATA(uc_kvm) *self)
 	}
 }
 
-/* verify SIEIC exit
+/*
+ * Handle the SIEIC exit
  * * fail on codes not expected in the test cases
+ * Returns if interception is handled / execution can be continued
+ */
+static void uc_skey_enable(FIXTURE_DATA(uc_kvm) *self)
+{
+	struct kvm_s390_sie_block *sie_block = self->sie_block;
+
+	/* disable KSS */
+	sie_block->cpuflags &= ~CPUSTAT_KSS;
+	/* disable skey inst interception */
+	sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE | ICTL_RRBE);
+}
+
+/*
+ * Handle the instruction intercept
+ * Returns if interception is handled / execution can be continued
+ */
+static bool uc_handle_insn_ic(FIXTURE_DATA(uc_kvm) *self)
+{
+	struct kvm_s390_sie_block *sie_block = self->sie_block;
+	int ilen = insn_length(sie_block->ipa >> 8);
+	struct kvm_run *run = self->run;
+
+	switch (run->s390_sieic.ipa) {
+	case 0xB229: /* ISKE */
+	case 0xB22b: /* SSKE */
+	case 0xB22a: /* RRBE */
+		uc_skey_enable(self);
+
+		/* rewind to reexecute intercepted instruction */
+		run->psw_addr = run->psw_addr - ilen;
+		pr_info("rewind guest addr to 0x%.16llx\n", run->psw_addr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * Handle the SIEIC exit
+ * * fail on codes not expected in the test cases
+ * Returns if interception is handled / execution can be continued
  */
 static bool uc_handle_sieic(FIXTURE_DATA(uc_kvm) * self)
 {
@@ -315,7 +384,10 @@ static bool uc_handle_sieic(FIXTURE_DATA(uc_kvm) * self)
 	case ICPT_INST:
 		/* end execution in caller on intercepted instruction */
 		pr_info("sie instruction interception\n");
-		return false;
+		return uc_handle_insn_ic(self);
+	case ICPT_KSS:
+		uc_skey_enable(self);
+		return true;
 	case ICPT_OPEREXC:
 		/* operation exception */
 		TEST_FAIL("sie exception on %.4x%.8x", sie_block->ipa, sie_block->ipb);
@@ -472,4 +544,73 @@ TEST_F(uc_kvm, uc_gprs)
 	ASSERT_EQ(1, sync_regs->gprs[0]);
 }
 
+TEST_F(uc_kvm, uc_skey)
+{
+	struct kvm_s390_sie_block *sie_block = self->sie_block;
+	struct kvm_sync_regs *sync_regs = &self->run->s.regs;
+	u64 test_vaddr = VM_MEM_SIZE - (SZ_1M / 2);
+	struct kvm_run *run = self->run;
+	const u8 skeyvalue = 0x34;
+
+	/* copy test_skey_asm to code_hva / code_gpa */
+	TH_LOG("copy code %p to vm mapped memory %p / %p",
+	       &test_skey_asm, (void *)self->code_hva, (void *)self->code_gpa);
+	memcpy((void *)self->code_hva, &test_skey_asm, PAGE_SIZE);
+
+	/* set register content for test_skey_asm to access not mapped memory */
+	sync_regs->gprs[1] = skeyvalue;
+	sync_regs->gprs[5] = self->base_gpa;
+	sync_regs->gprs[6] = test_vaddr;
+	run->kvm_dirty_regs |= KVM_SYNC_GPRS;
+
+	/* DAT disabled + 64 bit mode */
+	run->psw_mask = 0x0000000180000000ULL;
+	run->psw_addr = self->code_gpa;
+
+	ASSERT_EQ(0, uc_run_once(self));
+	ASSERT_EQ(true, uc_handle_exit(self));
+	ASSERT_EQ(1, sync_regs->gprs[0]);
+
+	/* ISKE */
+	ASSERT_EQ(0, uc_run_once(self));
+
+	/*
+	 * Bail out and skip the test after uc_skey_enable was executed but iske
+	 * is still intercepted. Instructions are not handled by the kernel.
+	 * Thus there is no need to test this here.
+	 */
+	TEST_ASSERT_EQ(0, sie_block->cpuflags & CPUSTAT_KSS);
+	TEST_ASSERT_EQ(0, sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE));
+	TEST_ASSERT_EQ(KVM_EXIT_S390_SIEIC, self->run->exit_reason);
+	TEST_ASSERT_EQ(ICPT_INST, sie_block->icptcode);
+	TEST_REQUIRE(sie_block->ipa != 0xb229);
+
+	/* ISKE contd. */
+	ASSERT_EQ(false, uc_handle_exit(self));
+	ASSERT_EQ(2, sync_regs->gprs[0]);
+	/* assert initial skey (ACC = 0, R & C = 1) */
+	ASSERT_EQ(0x06, sync_regs->gprs[1]);
+	uc_assert_diag44(self);
+
+	/* SSKE + ISKE */
+	sync_regs->gprs[1] = skeyvalue;
+	run->kvm_dirty_regs |= KVM_SYNC_GPRS;
+	ASSERT_EQ(0, uc_run_once(self));
+	ASSERT_EQ(false, uc_handle_exit(self));
+	ASSERT_EQ(3, sync_regs->gprs[0]);
+	ASSERT_EQ(skeyvalue, sync_regs->gprs[1]);
+	uc_assert_diag44(self);
+
+	/* RRBE + ISKE */
+	sync_regs->gprs[1] = skeyvalue;
+	run->kvm_dirty_regs |= KVM_SYNC_GPRS;
+	ASSERT_EQ(0, uc_run_once(self));
+	ASSERT_EQ(false, uc_handle_exit(self));
+	ASSERT_EQ(4, sync_regs->gprs[0]);
+	/* assert R reset but rest of skey unchanged */
+	ASSERT_EQ(skeyvalue & 0xfa, sync_regs->gprs[1]);
+	ASSERT_EQ(0, sync_regs->gprs[1] & 0x04);
+	uc_assert_diag44(self);
+}
+
 TEST_HARNESS_MAIN