KVM: selftests: Add memory size parameter to the demand paging test

Add an argument to allow the demand paging test to work on larger and
smaller guest sizes.
Signed-off-by: Ben Gardon <bgardon@google.com>
[Rewrote parse_size() to simplify and provide user more flexibility as
 to how sizes are input. Also fixed size overflow assert.]
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/Makefile

@@ -7,7 +7,7 @@ top_srcdir = ../../../..
 KSFT_KHDR_INSTALL := 1
 UNAME_M := $(shell uname -m)
 
-LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c
+LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c lib/test_util.c
 LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c
 LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
 LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c

tools/testing/selftests/kvm/demand_paging_test.c

@@ -34,6 +34,8 @@
 /* Default guest test virtual memory offset */
 #define DEFAULT_GUEST_TEST_MEM		0xc0000000
 
+#define DEFAULT_GUEST_TEST_MEM_SIZE (1 << 30) /* 1G */
+
 /*
  * Guest/Host shared variables. Ensure addr_gva2hva() and/or
  * sync_global_to/from_guest() are used when accessing from
@@ -276,11 +278,10 @@ static int setup_demand_paging(struct kvm_vm *vm,
 	return 0;
 }
 
-#define GUEST_MEM_SHIFT 30 /* 1G */
 #define PAGE_SHIFT_4K  12
 
 static void run_test(enum vm_guest_mode mode, bool use_uffd,
-		     useconds_t uffd_delay)
+		     useconds_t uffd_delay, uint64_t guest_memory_bytes)
 {
 	pthread_t vcpu_thread;
 	pthread_t uffd_handler_thread;
@@ -289,33 +290,40 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
 	int r;
 
 	/*
-	 * We reserve page table for 2 times of extra dirty mem which
-	 * will definitely cover the original (1G+) test range.  Here
-	 * we do the calculation with 4K page size which is the
-	 * smallest so the page number will be enough for all archs
-	 * (e.g., 64K page size guest will need even less memory for
-	 * page tables).
+	 * We reserve page table for twice the ammount of memory we intend
+	 * to use in the test region for demand paging. Here we do the
+	 * calculation with 4K page size which is the smallest so the page
+	 * number will be enough for all archs. (e.g., 64K page size guest
+	 * will need even less memory for page tables).
 	 */
 	vm = create_vm(mode, VCPU_ID,
-		       2ul << (GUEST_MEM_SHIFT - PAGE_SHIFT_4K),
+		       (2 * guest_memory_bytes) >> PAGE_SHIFT_4K,
 		       guest_code);
 
 	guest_page_size = vm_get_page_size(vm);
-	/*
-	 * A little more than 1G of guest page sized pages.  Cover the
-	 * case where the size is not aligned to 64 pages.
-	 */
-	guest_num_pages = (1ul << (GUEST_MEM_SHIFT -
-				   vm_get_page_shift(vm))) + 16;
+
+	TEST_ASSERT(guest_memory_bytes % guest_page_size == 0,
+		    "Guest memory size is not guest page size aligned.");
+
+	guest_num_pages = guest_memory_bytes / guest_page_size;
+
 #ifdef __s390x__
 	/* Round up to multiple of 1M (segment size) */
 	guest_num_pages = (guest_num_pages + 0xff) & ~0xffUL;
 #endif
+	/*
+	 * If there should be more memory in the guest test region than there
+	 * can be pages in the guest, it will definitely cause problems.
+	 */
+	TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),
+		    "Requested more guest memory than address space allows.\n"
+		    "    guest pages: %lx max gfn: %lx\n",
+		    guest_num_pages, vm_get_max_gfn(vm));
 
 	host_page_size = getpagesize();
-	host_num_pages = (guest_num_pages * guest_page_size) / host_page_size +
-			 !!((guest_num_pages * guest_page_size) %
-			    host_page_size);
+	TEST_ASSERT(guest_memory_bytes % host_page_size == 0,
+		    "Guest memory size is not host page size aligned.");
+	host_num_pages = guest_memory_bytes / host_page_size;
 
 	guest_test_phys_mem = (vm_get_max_gfn(vm) - guest_num_pages) *
 			      guest_page_size;
@@ -403,7 +411,8 @@ static void help(char *name)
 	int i;
 
 	puts("");
-	printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n", name);
+	printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n"
+	       "          [-b memory]\n", name);
 	printf(" -m: specify the guest mode ID to test\n"
 	       "     (default: test all supported modes)\n"
 	       "     This option may be used multiple times.\n"
@@ -417,6 +426,8 @@ static void help(char *name)
 	printf(" -d: add a delay in usec to the User Fault\n"
 	       "     FD handler to simulate demand paging\n"
 	       "     overheads. Ignored without -u.\n");
+	printf(" -b: specify the size of the memory region which should be\n"
+	       "     demand paged. e.g. 10M or 3G. Default: 1G\n");
 	puts("");
 	exit(0);
 }
@@ -424,6 +435,7 @@ static void help(char *name)
 int main(int argc, char *argv[])
 {
 	bool mode_selected = false;
+	uint64_t guest_memory_bytes = DEFAULT_GUEST_TEST_MEM_SIZE;
 	unsigned int mode;
 	int opt, i;
 	bool use_uffd = false;
@@ -450,7 +462,7 @@ int main(int argc, char *argv[])
 	guest_mode_init(VM_MODE_P40V48_4K, true, true);
 #endif
 
-	while ((opt = getopt(argc, argv, "hm:ud:")) != -1) {
+	while ((opt = getopt(argc, argv, "hm:ud:b:")) != -1) {
 		switch (opt) {
 		case 'm':
 			if (!mode_selected) {
@@ -471,6 +483,9 @@ int main(int argc, char *argv[])
 			TEST_ASSERT(uffd_delay >= 0,
 				    "A negative UFFD delay is not supported.");
 			break;
+		case 'b':
+			guest_memory_bytes = parse_size(optarg);
+			break;
 		case 'h':
 		default:
 			help(argv[0]);
@@ -484,7 +499,7 @@ int main(int argc, char *argv[])
 		TEST_ASSERT(guest_modes[i].supported,
 			    "Guest mode ID %d (%s) not supported.",
 			    i, vm_guest_mode_string(i));
-		run_test(i, use_uffd, uffd_delay);
+		run_test(i, use_uffd, uffd_delay, guest_memory_bytes);
 	}
 
 	return 0;

tools/testing/selftests/kvm/include/test_util.h

@@ -39,4 +39,6 @@ void test_assert(bool exp, const char *exp_str,
 		    #a, #b, #a, (unsigned long) __a, #b, (unsigned long) __b); \
 } while (0)
 
+size_t parse_size(const char *size);
+
 #endif /* SELFTEST_KVM_TEST_UTIL_H */

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

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * tools/testing/selftests/kvm/lib/test_util.c
+ *
+ * Copyright (C) 2020, Google LLC.
+ */
+#include <stdlib.h>
+#include <ctype.h>
+#include <limits.h>
+#include "test_util.h"
+
+/*
+ * Parses "[0-9]+[kmgt]?".
+ */
+size_t parse_size(const char *size)
+{
+	size_t base;
+	char *scale;
+	int shift = 0;
+
+	TEST_ASSERT(size && isdigit(size[0]), "Need at least one digit in '%s'", size);
+
+	base = strtoull(size, &scale, 0);
+
+	TEST_ASSERT(base != ULLONG_MAX, "Overflow parsing size!");
+
+	switch (tolower(*scale)) {
+	case 't':
+		shift = 40;
+		break;
+	case 'g':
+		shift = 30;
+		break;
+	case 'm':
+		shift = 20;
+		break;
+	case 'k':
+		shift = 10;
+		break;
+	case 'b':
+	case '\0':
+		shift = 0;
+		break;
+	default:
+		TEST_ASSERT(false, "Unknown size letter %c", *scale);
+	}
+
+	TEST_ASSERT((base << shift) >> shift == base, "Overflow scaling size!");
+
+	return base << shift;
+}