KVM: selftests: aarch64: vPMU register test for unimplemented counters

Add a new test case to the vpmu_counter_access test to check
if PMU registers or their bits for unimplemented counters are not
accessible or are RAZ, as expected.
Signed-off-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231020214053.2144305-12-rananta@google.com
[Oliver: fix issues relating to exception return address]
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c

@@ -5,8 +5,9 @@
  * Copyright (c) 2023 Google LLC.
  *
  * This test checks if the guest can see the same number of the PMU event
- * counters (PMCR_EL0.N) that userspace sets, and if the guest can access
- * those counters.
+ * counters (PMCR_EL0.N) that userspace sets, if the guest can access
+ * those counters, and if the guest is prevented from accessing any
+ * other counters.
  * This test runs only when KVM_CAP_ARM_PMU_V3 is supported on the host.
  */
 #include <kvm_util.h>
@@ -287,25 +288,74 @@ static void test_access_pmc_regs(struct pmc_accessor *acc, int pmc_idx)
 		       pmc_idx, PMC_ACC_TO_IDX(acc), read_data, write_data);
 }
 
+#define INVALID_EC	(-1ul)
+uint64_t expected_ec = INVALID_EC;
+
 static void guest_sync_handler(struct ex_regs *regs)
 {
 	uint64_t esr, ec;
 
 	esr = read_sysreg(esr_el1);
 	ec = (esr >> ESR_EC_SHIFT) & ESR_EC_MASK;
-	__GUEST_ASSERT(0, "PC: 0x%lx; ESR: 0x%lx; EC: 0x%lx", regs->pc, esr, ec);
+
+	__GUEST_ASSERT(expected_ec == ec,
+			"PC: 0x%lx; ESR: 0x%lx; EC: 0x%lx; EC expected: 0x%lx",
+			regs->pc, esr, ec, expected_ec);
+
+	/* skip the trapping instruction */
+	regs->pc += 4;
+
+	/* Use INVALID_EC to indicate an exception occurred */
+	expected_ec = INVALID_EC;
+}
+
+/*
+ * Run the given operation that should trigger an exception with the
+ * given exception class. The exception handler (guest_sync_handler)
+ * will reset op_end_addr to 0, expected_ec to INVALID_EC, and skip
+ * the instruction that trapped.
+ */
+#define TEST_EXCEPTION(ec, ops)				\
+({							\
+	GUEST_ASSERT(ec != INVALID_EC);			\
+	WRITE_ONCE(expected_ec, ec);			\
+	dsb(ish);					\
+	ops;						\
+	GUEST_ASSERT(expected_ec == INVALID_EC);	\
+})
+
+/*
+ * Tests for reading/writing registers for the unimplemented event counter
+ * specified by @pmc_idx (>= PMCR_EL0.N).
+ */
+static void test_access_invalid_pmc_regs(struct pmc_accessor *acc, int pmc_idx)
+{
+	/*
+	 * Reading/writing the event count/type registers should cause
+	 * an UNDEFINED exception.
+	 */
+	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->read_cntr(pmc_idx));
+	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->write_cntr(pmc_idx, 0));
+	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->read_typer(pmc_idx));
+	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->write_typer(pmc_idx, 0));
+	/*
+	 * The bit corresponding to the (unimplemented) counter in
+	 * {PMCNTEN,PMINTEN,PMOVS}{SET,CLR} registers should be RAZ.
+	 */
+	test_bitmap_pmu_regs(pmc_idx, 1);
+	test_bitmap_pmu_regs(pmc_idx, 0);
 }
 
 /*
  * The guest is configured with PMUv3 with @expected_pmcr_n number of
  * event counters.
  * Check if @expected_pmcr_n is consistent with PMCR_EL0.N, and
- * if reading/writing PMU registers for implemented counters works
- * as expected.
+ * if reading/writing PMU registers for implemented or unimplemented
+ * counters works as expected.
  */
 static void guest_code(uint64_t expected_pmcr_n)
 {
-	uint64_t pmcr, pmcr_n;
+	uint64_t pmcr, pmcr_n, unimp_mask;
 	int i, pmc;
 
 	__GUEST_ASSERT(expected_pmcr_n <= ARMV8_PMU_MAX_GENERAL_COUNTERS,
@@ -320,15 +370,33 @@ static void guest_code(uint64_t expected_pmcr_n)
 			"Expected PMCR.N: 0x%lx, PMCR.N: 0x%lx",
 			expected_pmcr_n, pmcr_n);
 
+	/*
+	 * Make sure that (RAZ) bits corresponding to unimplemented event
+	 * counters in {PMCNTEN,PMINTEN,PMOVS}{SET,CLR} registers are reset
+	 * to zero.
+	 * (NOTE: bits for implemented event counters are reset to UNKNOWN)
+	 */
+	unimp_mask = GENMASK_ULL(ARMV8_PMU_MAX_GENERAL_COUNTERS - 1, pmcr_n);
+	check_bitmap_pmu_regs(unimp_mask, false);
+
 	/*
 	 * Tests for reading/writing PMU registers for implemented counters.
-	 * Use each combination of PMEVT{CNTR,TYPER}<n>_EL0 accessor functions.
+	 * Use each combination of PMEV{CNTR,TYPER}<n>_EL0 accessor functions.
 	 */
 	for (i = 0; i < ARRAY_SIZE(pmc_accessors); i++) {
 		for (pmc = 0; pmc < pmcr_n; pmc++)
 			test_access_pmc_regs(&pmc_accessors[i], pmc);
 	}
 
+	/*
+	 * Tests for reading/writing PMU registers for unimplemented counters.
+	 * Use each combination of PMEV{CNTR,TYPER}<n>_EL0 accessor functions.
+	 */
+	for (i = 0; i < ARRAY_SIZE(pmc_accessors); i++) {
+		for (pmc = pmcr_n; pmc < ARMV8_PMU_MAX_GENERAL_COUNTERS; pmc++)
+			test_access_invalid_pmc_regs(&pmc_accessors[i], pmc);
+	}
+
 	GUEST_DONE();
 }
 

tools/testing/selftests/kvm/include/aarch64/processor.h

@@ -104,6 +104,7 @@ enum {
 #define ESR_EC_SHIFT		26
 #define ESR_EC_MASK		(ESR_EC_NUM - 1)
 
+#define ESR_EC_UNKNOWN		0x0
 #define ESR_EC_SVC64		0x15
 #define ESR_EC_IABT		0x21
 #define ESR_EC_DABT		0x25