Merge tag 'for-linus-6.0' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
 "A small fix to the reported set of supported CPUID bits, and selftests
  fixes:

   - Skip tests that require EPT when it is not available

   - Do not hang when a test fails with an empty stack trace

   - avoid spurious failure when running access_tracking_perf_test in a
     KVM guest

   - work around GCC's tendency to optimize loops into mem*() functions,
     which breaks because the guest code in selftests cannot call into
     PLTs

   - fix -Warray-bounds error in fix_hypercall_test"

* tag 'for-linus-6.0' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: selftests: Compare insn opcodes directly in fix_hypercall_test
  KVM: selftests: Implement memcmp(), memcpy(), and memset() for guest use
  KVM: x86: Hide IA32_PLATFORM_DCA_CAP[31:0] from the guest
  KVM: selftests: Gracefully handle empty stack traces
  KVM: selftests: replace assertion with warning in access_tracking_perf_test
  KVM: selftests: Skip tests that require EPT when it is not available

arch/x86/kvm/cpuid.c

@@ -902,8 +902,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 			entry->edx = 0;
 		}
 		break;
-	case 9:
-		break;
 	case 0xa: { /* Architectural Performance Monitoring */
 		union cpuid10_eax eax;
 		union cpuid10_edx edx;

tools/testing/selftests/kvm/Makefile

@@ -48,6 +48,8 @@ LIBKVM += lib/rbtree.c
 LIBKVM += lib/sparsebit.c
 LIBKVM += lib/test_util.c
 
+LIBKVM_STRING += lib/string_override.c
+
 LIBKVM_x86_64 += lib/x86_64/apic.c
 LIBKVM_x86_64 += lib/x86_64/handlers.S
 LIBKVM_x86_64 += lib/x86_64/perf_test_util.c
@@ -220,7 +222,8 @@ LIBKVM_C := $(filter %.c,$(LIBKVM))
 LIBKVM_S := $(filter %.S,$(LIBKVM))
 LIBKVM_C_OBJ := $(patsubst %.c, $(OUTPUT)/%.o, $(LIBKVM_C))
 LIBKVM_S_OBJ := $(patsubst %.S, $(OUTPUT)/%.o, $(LIBKVM_S))
-LIBKVM_OBJS = $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ)
+LIBKVM_STRING_OBJ := $(patsubst %.c, $(OUTPUT)/%.o, $(LIBKVM_STRING))
+LIBKVM_OBJS = $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ) $(LIBKVM_STRING_OBJ)
 
 EXTRA_CLEAN += $(LIBKVM_OBJS) cscope.*
 
@@ -231,6 +234,12 @@ $(LIBKVM_C_OBJ): $(OUTPUT)/%.o: %.c
 $(LIBKVM_S_OBJ): $(OUTPUT)/%.o: %.S
 	$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
 
+# Compile the string overrides as freestanding to prevent the compiler from
+# generating self-referential code, e.g. without "freestanding" the compiler may
+# "optimize" memcmp() by invoking memcmp(), thus causing infinite recursion.
+$(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
+	$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
+
 x := $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
 $(TEST_GEN_PROGS): $(LIBKVM_OBJS)
 $(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)

tools/testing/selftests/kvm/access_tracking_perf_test.c

@@ -31,8 +31,9 @@
  * These limitations are worked around in this test by using a large enough
  * region of memory for each vCPU such that the number of translations cached in
  * the TLB and the number of pages held in pagevecs are a small fraction of the
- * overall workload. And if either of those conditions are not true this test
- * will fail rather than silently passing.
+ * overall workload. And if either of those conditions are not true (for example
+ * in nesting, where TLB size is unlimited) this test will print a warning
+ * rather than silently passing.
  */
 #include <inttypes.h>
 #include <limits.h>
@@ -172,16 +173,22 @@ static void mark_vcpu_memory_idle(struct kvm_vm *vm,
 		    vcpu_idx, no_pfn, pages);
 
 	/*
-	 * Test that at least 90% of memory has been marked idle (the rest might
-	 * not be marked idle because the pages have not yet made it to an LRU
-	 * list or the translations are still cached in the TLB). 90% is
+	 * Check that at least 90% of memory has been marked idle (the rest
+	 * might not be marked idle because the pages have not yet made it to an
+	 * LRU list or the translations are still cached in the TLB). 90% is
 	 * arbitrary; high enough that we ensure most memory access went through
 	 * access tracking but low enough as to not make the test too brittle
 	 * over time and across architectures.
+	 *
+	 * Note that when run in nested virtualization, this check will trigger
+	 * much more frequently because TLB size is unlimited and since no flush
+	 * happens, much more pages are cached there and guest won't see the
+	 * "idle" bit cleared.
 	 */
-	TEST_ASSERT(still_idle < pages / 10,
-		    "vCPU%d: Too many pages still idle (%"PRIu64 " out of %"
-		    PRIu64 ").\n",
+	if (still_idle < pages / 10)
+		printf("WARNING: vCPU%d: Too many pages still idle (%" PRIu64
+		       "out of %" PRIu64 "), this will affect performance results"
+		       ".\n",
 		       vcpu_idx, still_idle, pages);
 
 	close(page_idle_fd);

tools/testing/selftests/kvm/include/x86_64/vmx.h

@@ -617,6 +617,7 @@ void nested_map_memslot(struct vmx_pages *vmx, struct kvm_vm *vm,
 			uint32_t memslot);
 void nested_identity_map_1g(struct vmx_pages *vmx, struct kvm_vm *vm,
 			    uint64_t addr, uint64_t size);
+bool kvm_vm_has_ept(struct kvm_vm *vm);
 void prepare_eptp(struct vmx_pages *vmx, struct kvm_vm *vm,
 		  uint32_t eptp_memslot);
 void prepare_virtualize_apic_accesses(struct vmx_pages *vmx, struct kvm_vm *vm);

tools/testing/selftests/kvm/lib/assert.c

@@ -22,7 +22,7 @@ static void test_dump_stack(void)
 	 * Build and run this command:
 	 *
 	 *	addr2line -s -e /proc/$PPID/exe -fpai {backtrace addresses} | \
-	 *		grep -v test_dump_stack | cat -n 1>&2
+	 *		cat -n 1>&2
 	 *
 	 * Note that the spacing is different and there's no newline.
 	 */
@@ -36,18 +36,24 @@ static void test_dump_stack(void)
 		 n * (((sizeof(void *)) * 2) + 1) +
 		 /* Null terminator: */
 		 1];
-	char *c;
+	char *c = cmd;
 
 	n = backtrace(stack, n);
-	c = &cmd[0];
-	c += sprintf(c, "%s", addr2line);
 	/*
-	 * Skip the first 3 frames: backtrace, test_dump_stack, and
-	 * test_assert. We hope that backtrace isn't inlined and the other two
-	 * we've declared noinline.
+	 * Skip the first 2 frames, which should be test_dump_stack() and
+	 * test_assert(); both of which are declared noinline.  Bail if the
+	 * resulting stack trace would be empty. Otherwise, addr2line will block
+	 * waiting for addresses to be passed in via stdin.
 	 */
+	if (n <= 2) {
+		fputs("  (stack trace empty)\n", stderr);
+		return;
+	}
+
+	c += sprintf(c, "%s", addr2line);
 	for (i = 2; i < n; i++)
 		c += sprintf(c, " %lx", ((unsigned long) stack[i]) - 1);
+
 	c += sprintf(c, "%s", pipeline);
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-result"

tools/testing/selftests/kvm/lib/string_override.c

+// SPDX-License-Identifier: GPL-2.0-only
+#include <stddef.h>
+
+/*
+ * Override the "basic" built-in string helpers so that they can be used in
+ * guest code.  KVM selftests don't support dynamic loading in guest code and
+ * will jump into the weeds if the compiler decides to insert an out-of-line
+ * call via the PLT.
+ */
+int memcmp(const void *cs, const void *ct, size_t count)
+{
+	const unsigned char *su1, *su2;
+	int res = 0;
+
+	for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--) {
+		if ((res = *su1 - *su2) != 0)
+			break;
+	}
+	return res;
+}
+
+void *memcpy(void *dest, const void *src, size_t count)
+{
+	char *tmp = dest;
+	const char *s = src;
+
+	while (count--)
+		*tmp++ = *s++;
+	return dest;
+}
+
+void *memset(void *s, int c, size_t count)
+{
+	char *xs = s;
+
+	while (count--)
+		*xs++ = c;
+	return s;
+}

tools/testing/selftests/kvm/lib/x86_64/vmx.c

@@ -5,6 +5,8 @@
  * Copyright (C) 2018, Google LLC.
  */
 
+#include <asm/msr-index.h>
+
 #include "test_util.h"
 #include "kvm_util.h"
 #include "processor.h"
@@ -542,9 +544,27 @@ void nested_identity_map_1g(struct vmx_pages *vmx, struct kvm_vm *vm,
 	__nested_map(vmx, vm, addr, addr, size, PG_LEVEL_1G);
 }
 
+bool kvm_vm_has_ept(struct kvm_vm *vm)
+{
+	struct kvm_vcpu *vcpu;
+	uint64_t ctrl;
+
+	vcpu = list_first_entry(&vm->vcpus, struct kvm_vcpu, list);
+	TEST_ASSERT(vcpu, "Cannot determine EPT support without vCPUs.\n");
+
+	ctrl = vcpu_get_msr(vcpu, MSR_IA32_VMX_TRUE_PROCBASED_CTLS) >> 32;
+	if (!(ctrl & CPU_BASED_ACTIVATE_SECONDARY_CONTROLS))
+		return false;
+
+	ctrl = vcpu_get_msr(vcpu, MSR_IA32_VMX_PROCBASED_CTLS2) >> 32;
+	return ctrl & SECONDARY_EXEC_ENABLE_EPT;
+}
+
 void prepare_eptp(struct vmx_pages *vmx, struct kvm_vm *vm,
 		  uint32_t eptp_memslot)
 {
+	TEST_REQUIRE(kvm_vm_has_ept(vm));
+
 	vmx->eptp = (void *)vm_vaddr_alloc_page(vm);
 	vmx->eptp_hva = addr_gva2hva(vm, (uintptr_t)vmx->eptp);
 	vmx->eptp_gpa = addr_gva2gpa(vm, (uintptr_t)vmx->eptp);

tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c

@@ -14,6 +14,9 @@
 #include "kvm_util.h"
 #include "processor.h"
 
+/* VMCALL and VMMCALL are both 3-byte opcodes. */
+#define HYPERCALL_INSN_SIZE	3
+
 static bool ud_expected;
 
 static void guest_ud_handler(struct ex_regs *regs)
@@ -22,7 +25,7 @@ static void guest_ud_handler(struct ex_regs *regs)
 	GUEST_DONE();
 }
 
-extern unsigned char svm_hypercall_insn;
+extern uint8_t svm_hypercall_insn[HYPERCALL_INSN_SIZE];
 static uint64_t svm_do_sched_yield(uint8_t apic_id)
 {
 	uint64_t ret;
@@ -39,7 +42,7 @@ static uint64_t svm_do_sched_yield(uint8_t apic_id)
 	return ret;
 }
 
-extern unsigned char vmx_hypercall_insn;
+extern uint8_t vmx_hypercall_insn[HYPERCALL_INSN_SIZE];
 static uint64_t vmx_do_sched_yield(uint8_t apic_id)
 {
 	uint64_t ret;
@@ -56,30 +59,20 @@ static uint64_t vmx_do_sched_yield(uint8_t apic_id)
 	return ret;
 }
 
-static void assert_hypercall_insn(unsigned char *exp_insn, unsigned char *obs_insn)
-{
-	uint32_t exp = 0, obs = 0;
-
-	memcpy(&exp, exp_insn, sizeof(exp));
-	memcpy(&obs, obs_insn, sizeof(obs));
-
-	GUEST_ASSERT_EQ(exp, obs);
-}
-
 static void guest_main(void)
 {
-	unsigned char *native_hypercall_insn, *hypercall_insn;
+	uint8_t *native_hypercall_insn, *hypercall_insn;
 	uint8_t apic_id;
 
 	apic_id = GET_APIC_ID_FIELD(xapic_read_reg(APIC_ID));
 
 	if (is_intel_cpu()) {
-		native_hypercall_insn = &vmx_hypercall_insn;
-		hypercall_insn = &svm_hypercall_insn;
+		native_hypercall_insn = vmx_hypercall_insn;
+		hypercall_insn = svm_hypercall_insn;
 		svm_do_sched_yield(apic_id);
 	} else if (is_amd_cpu()) {
-		native_hypercall_insn = &svm_hypercall_insn;
-		hypercall_insn = &vmx_hypercall_insn;
+		native_hypercall_insn = svm_hypercall_insn;
+		hypercall_insn = vmx_hypercall_insn;
 		vmx_do_sched_yield(apic_id);
 	} else {
 		GUEST_ASSERT(0);
@@ -87,8 +80,13 @@ static void guest_main(void)
 		return;
 	}
 
+	/*
+	 * The hypercall didn't #UD (guest_ud_handler() signals "done" if a #UD
+	 * occurs).  Verify that a #UD is NOT expected and that KVM patched in
+	 * the native hypercall.
+	 */
 	GUEST_ASSERT(!ud_expected);
-	assert_hypercall_insn(native_hypercall_insn, hypercall_insn);
+	GUEST_ASSERT(!memcmp(native_hypercall_insn, hypercall_insn, HYPERCALL_INSN_SIZE));
 	GUEST_DONE();
 }